JP4931025B2 - Stabilized reference electrode circuit - Google Patents

Stabilized reference electrode circuit Download PDF

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JP4931025B2
JP4931025B2 JP2009004288A JP2009004288A JP4931025B2 JP 4931025 B2 JP4931025 B2 JP 4931025B2 JP 2009004288 A JP2009004288 A JP 2009004288A JP 2009004288 A JP2009004288 A JP 2009004288A JP 4931025 B2 JP4931025 B2 JP 4931025B2
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純 城間
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Description

本発明は、燃料電池などの電気化学装置において使用される参照電極回路に関し、特に、動的水素電極（ＤＨＥ）の電位を安定させることができる安定化参照電極回路に関する。   The present invention relates to a reference electrode circuit used in an electrochemical device such as a fuel cell, and more particularly to a stabilized reference electrode circuit capable of stabilizing the potential of a dynamic hydrogen electrode (DHE).

電気化学実験や電気化学装置においては、目的とする反応を起こさせる電極（以下「作用極」と記す）を電解液に浸け、さまざまな電流や電圧を加える。その時、電流を流す相手として別の電極（以下「対極」と記す）を用いる。通常、作用極と電解液界面との電位差に着目するため、電解液の電位をモニターするための電極（以下「参照極」と記す）をさらに導入し、作用極−対極間の電圧ではなく、作用極−参照極間の電圧を記録する。   In electrochemical experiments and electrochemical devices, an electrode (hereinafter referred to as a “working electrode”) that causes a target reaction is immersed in an electrolytic solution, and various currents and voltages are applied. At that time, another electrode (hereinafter referred to as “counter electrode”) is used as a partner through which a current flows. Usually, in order to pay attention to the potential difference between the working electrode and the electrolyte solution interface, an electrode for monitoring the potential of the electrolyte solution (hereinafter referred to as “reference electrode”) is further introduced, not the voltage between the working electrode and the counter electrode, Record the voltage between the working and reference electrodes.

目的に応じていろいろな参照極が知られている。いずれも何らかの電気化学反応の平衡を用い、その反応により、電解液に対する電位が決まる。例えば、よく用いられる銀／塩化銀電極の場合、電解液に対し約０．２Ｖの電位を示す。   Various reference poles are known depending on the purpose. In any case, some kind of electrochemical reaction equilibrium is used, and the electric potential with respect to the electrolytic solution is determined by the reaction. For example, a commonly used silver / silver chloride electrode exhibits a potential of about 0.2 V with respect to the electrolyte.

可逆水素電極（以下「ＲＨＥ」と記す）と呼ばれる参照極は、水素の酸化還元平衡を用いるものであり、約０Ｖ（正確には電解液中の水素イオン濃度（ｐＨ）に応じた電位）を示すことが知られている。   A reference electrode called a reversible hydrogen electrode (hereinafter referred to as “RHE”) uses a redox equilibrium of hydrogen, and has a potential of about 0 V (more precisely, a potential corresponding to the hydrogen ion concentration (pH) in the electrolyte). It is known to show.

また、動的水素電極（以下「ＤＨＥ」と記す）と呼ばれる参照極も知られている（下記特許文献１、非特許文献１、２参照）。ＤＨＥは、ＲＨＥの代わりに簡易的に用いられるものであり、２つの電極で構成される。これら２つの電極間に微小な定電流を印加して水の電気分解を起こさせ、陽極側で酸素を発生させ、陰極側で水素を発生させると、このときの陰極の電位がほぼＲＨＥの電位と等しくなる。ＤＨＥを用いる場合、この現象を利用して陰極の電位を基準電位として使用する。ＤＨＥでは、反応が進行しているため、平衡状態とは言えず、真のＲＨＥ電位とは若干ずれがあることが知られているが、これは実測により後で補正することができる。   A reference electrode called a dynamic hydrogen electrode (hereinafter referred to as “DHE”) is also known (see Patent Document 1 and Non-Patent Documents 1 and 2 below). DHE is simply used instead of RHE, and is composed of two electrodes. When a small constant current is applied between these two electrodes to cause electrolysis of water, oxygen is generated on the anode side, and hydrogen is generated on the cathode side, the potential of the cathode at this time is approximately the potential of RHE. Is equal to When using DHE, the cathode potential is used as a reference potential by utilizing this phenomenon. In DHE, since the reaction proceeds, it cannot be said that it is in an equilibrium state, and it is known that there is a slight deviation from the true RHE potential. However, this can be corrected later by actual measurement.

特開２００６−３３９０８４号公報JP 2006-339084 A

J. Giner, J. Electrochem. Soc., 第１１１巻, １９６４年, ｐ．３７６−３７７J. Giner, J. Electrochem. Soc., 111, 1964, p. 376-377 A. Kuver, I. Vogel, W. Vielstich, J. Power Sources, 第５２巻, １９９４年, ｐ．７７A. Kuver, I. Vogel, W. Vielstich, J. Power Sources, Vol. 52, 1994, p. 77

しかし、ＤＨＥでは、電位が安定しない（ゆらぐ）という問題がある。即ち、精度の高い実験を行うためには、電解液電位の変化を捉えるための参照極電位は、本来、電解液の電位の変化に追随して平行に変化する必要がある（「本来あるべき参照極電位」）が、ＤＨＥを用いると、これに微小な電位ゆらぎが加算されたものが出力される。実際の測定結果によると、数十秒オーダーの期間で最大１０ｍＶ程度変化することが分かっている。従って、このことが、高い精度が要求される電気化学実験や電気化学装置において、ＤＨＥ
を参照極として使用することが困難な原因となっていた。 However, DHE has a problem that the potential is not stable (fluctuates). In other words, in order to perform a highly accurate experiment, the reference electrode potential for capturing the change in the electrolyte potential must originally change in parallel with the change in the potential of the electrolyte ( When the DHE is used as the reference electrode potential "), a value obtained by adding a small potential fluctuation to this is output. According to actual measurement results, it is known that the maximum change is about 10 mV in a period of several tens of seconds. Therefore, this is the DHE in electrochemical experiments and electrochemical devices that require high accuracy.
Is a difficult cause to use as a reference electrode.

本発明は、上記の課題を解決すべく、電気化学実験や電気化学装置において使用される動的水素電極（ＤＨＥ）の電位を安定させることができる安定化参照電極回路を提供することを目的とする。   The present invention aims to provide a stabilized reference electrode circuit capable of stabilizing the potential of a dynamic hydrogen electrode (DHE) used in electrochemical experiments and electrochemical devices in order to solve the above-described problems. To do.

本発明の目的は、以下の手段によって達成される。ここで、本発明の理解を容易にするために符号を記載しているが、これは本発明を実施の形態に限定することを意図したものではない。   The object of the present invention is achieved by the following means. Here, reference numerals are used to facilitate understanding of the present invention, but this is not intended to limit the present invention to the embodiments.

即ち、本発明に係る第１の安定化参照電極回路は、動的水素電極を用いた安定化参照電極回路であって、
電解液（１）に浸けられ、前記動的水素電極の陰極である第１電極（Ａ）及び前記動的水素電極の陽極である第２電極（Ｂ）と、
前記第１及び第２電極（Ａ、Ｂ）の間に定電流を印加する定電流電源（２）と、
前記第１電極の電位が入力される第１電圧フォロワ回路（ＶＦ１）と、
前記電解液に浸けられた付加電極（Ｃ）と、
前記付加電極（Ｃ）の電位が入力される第２電圧フォロワ回路（ＶＦ２）と
前記第１及び第２電圧フォロワ回路の出力電位が入力される減算回路（３）と
前記減算回路（３）の出力電位が入力される平滑回路（４）と、
前記平滑回路（４）及び前記第２電圧フォロワ回路（ＶＲＦ２）の出力電位が入力される加算回路（５）とを備え、
前記第１及び第２電圧フォロワ回路の各々が、入力インピーダンスよりも小さい出力インピーダンスを有し、
前記減算回路（３）が、入力される前記第１電圧フォロワ回路（ＶＦ１）の出力電位（ＥＡ’）から前記第２電圧フォロワ回路（ＶＦ２）の出力電位（ＥＣ’）を減算した電位（ＥＡ’−ＥＣ’）を出力し、
前記平滑回路（４）が、前記減算回路（３）の出力電位を平滑して出力し、
前記加算回路（５）が、前記平滑回路（４）及び前記第２電圧フォロワ回路（ＶＦ２）の出力電位を加算して出力することを特徴としている。 That is, the first stabilized reference electrode circuit according to the present invention is a stabilized reference electrode circuit using a dynamic hydrogen electrode,
A first electrode (A) which is immersed in an electrolytic solution (1) and is a cathode of the dynamic hydrogen electrode; and a second electrode (B) which is an anode of the dynamic hydrogen electrode;
A constant current power source (2) for applying a constant current between the first and second electrodes (A, B);
A first voltage follower circuit (VF1) to which the potential of the first electrode is input;
An additional electrode (C) immersed in the electrolytic solution;
A second voltage follower circuit (VF2) to which the potential of the additional electrode (C) is input; a subtraction circuit (3) to which the output potentials of the first and second voltage follower circuits are input; and the subtraction circuit (3). A smoothing circuit (4) to which an output potential is input;
An addition circuit (5) to which the output potentials of the smoothing circuit (4) and the second voltage follower circuit (VRF2) are input;
Each of the first and second voltage follower circuits has an output impedance less than an input impedance;
The potential obtained by subtracting the output potential (E C ′) of the second voltage follower circuit (VF2) from the output potential (E A ′) of the first voltage follower circuit (VF1) input by the subtracting circuit (3). (E A '-E C ')
The smoothing circuit (4) smoothes and outputs the output potential of the subtracting circuit (3),
The addition circuit (5) adds the output potentials of the smoothing circuit (4) and the second voltage follower circuit (VF2) and outputs the result.

また、本発明に係る第２の安定化参照電極回路は、動的水素電極（ＤＨＥ）を用いた安定化参照電極回路であって、
電解液（１）に浸けられ、前記動的水素電極の陰極である第１電極（Ａ）及び前記動的水素電極の陽極である第２電極（Ｂ）と、
前記第１及び第２電極（Ａ、Ｂ）の間に定電流を印加する定電流電源（２）と、
前記第１電極の電位が入力される第１電圧フォロワ回路（ＶＦ１）と、
前記電解液に浸けられた付加電極（Ｃ）と、
前記付加電極（Ｃ）の電位が入力される第２電圧フォロワ回路（ＶＦ２）と
前記第１及び第２電圧フォロワ回路の出力電位が入力される第１減算回路（３）と
前記第１減算回路（３）の出力電位が入力される平滑回路（４）と、
前記平滑回路（４）及び前記第２電圧フォロワ回路（ＶＲＦ２）の出力電位が入力される第２減算回路（５）とを備え、
前記第１減算回路（３）が、入力される前記第１電圧フォロワ回路（ＶＦ１）の出力電位（ＥＡ’）から前記第２電圧フォロワ回路（ＶＦ２）の出力電位（ＥＣ’）を減算した電位（ＥＡ’−ＥＣ’）を出力し、
前記平滑回路（４）が、前記第１減算回路（３）の出力電位を平滑し、且つ極性を反転させて出力し、
前記第２減算回路（５）が、前記第２電圧フォロワ回路（ＶＦ２）の出力電位から、前
記平滑回路（４）の出力電位を減算して出力することを特徴としている。 A second stabilized reference electrode circuit according to the present invention is a stabilized reference electrode circuit using a dynamic hydrogen electrode (DHE),
A first electrode (A) which is immersed in an electrolytic solution (1) and is a cathode of the dynamic hydrogen electrode; and a second electrode (B) which is an anode of the dynamic hydrogen electrode;
A constant current power source (2) for applying a constant current between the first and second electrodes (A, B);
A first voltage follower circuit (VF1) to which the potential of the first electrode is input;
An additional electrode (C) immersed in the electrolytic solution;
A second voltage follower circuit (VF2) to which the potential of the additional electrode (C) is input; a first subtraction circuit (3) to which the output potentials of the first and second voltage follower circuits are input; and the first subtraction circuit. A smoothing circuit (4) to which the output potential of (3) is input;
A second subtracting circuit (5) to which the output potential of the smoothing circuit (4) and the second voltage follower circuit (VRF2) is input;
The first subtracting circuit (3) subtracts the output potential (E C ') of the second voltage follower circuit (VF2) from the output potential (E A ') of the input first voltage follower circuit (VF1). outputs the potential (E a '-E C') ,
The smoothing circuit (4) smoothes the output potential of the first subtracting circuit (3) and inverts the polarity to output it,
The second subtracting circuit (5) subtracts the output potential of the smoothing circuit (4) from the output potential of the second voltage follower circuit (VF2) and outputs the result.

また、本発明に係る第３の安定化参照電極回路は、上記の第１又は第２の安定化参照電極回路において、前記平滑回路の時定数が、２０秒以上１００秒以下であることができる。   Further, in the third stabilized reference electrode circuit according to the present invention, in the first or second stabilized reference electrode circuit, a time constant of the smoothing circuit may be 20 seconds or more and 100 seconds or less. .

上記の第１〜第３の安定化参照電極回路の何れかにおいて、前記付加電極は、縦１０ｍｍ以上１００ｍｍ以下、横２ｍｍ以上２０ｍｍ以下の板状体であり、カーボンで形成されていることができる。   In any one of the first to third stabilization reference electrode circuits, the additional electrode is a plate-like body having a length of 10 mm to 100 mm and a width of 2 mm to 20 mm, and can be formed of carbon. .

本発明によれば、電気化学実験や電気化学装置において、参照極として用いられる動的水素電極（ＤＨＥ）の電位を安定させることができる。従って、より精度の高い電気化学装置を提供することができ、より精度の高い電気化学実験を行うことができる。   According to the present invention, the potential of a dynamic hydrogen electrode (DHE) used as a reference electrode in an electrochemical experiment or an electrochemical apparatus can be stabilized. Therefore, a more accurate electrochemical device can be provided, and a more accurate electrochemical experiment can be performed.

本発明の実施の形態に係る安定化参照電極回路を示す概略構成図である。It is a schematic block diagram which shows the stabilization reference electrode circuit which concerns on embodiment of this invention. 図１に示した安定化参照電極回路における電位波形を示すグラフである。It is a graph which shows the electric potential waveform in the stabilization reference electrode circuit shown in FIG. 実験した構成を示す図であり、平滑回路を用いない構成を示す。It is a figure which shows the structure which experimented and shows the structure which does not use a smoothing circuit. 実験した構成を示す図であり、平滑回路を用いた構成（本発明の安定化参照電極回路に対応）を示す。It is a figure which shows the structure experimented, and shows the structure (corresponding | compatible to the stabilization reference electrode circuit of this invention) using the smoothing circuit. 実験結果を示すグラフであり、検証用参照極（銀／塩化銀電極）を用いて測定した作用極電位の経時変化を示す。It is a graph which shows an experimental result, and shows a time-dependent change of the working electrode potential measured using the reference electrode for verification (silver / silver chloride electrode).

以下、本発明に係る実施の形態を、添付した図面に基づいて説明する。   DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.

図１は、本発明の実施の形態に係る安定化参照電極回路を示す概略構成図である。本安定化参照電極回路は、
電解液１に浸けられ、動的水素電極ＤＨＥを構成する第１電極（陰極）Ａ及び第２電極（陽極）Ｂと、
第１及び第２電極Ａ、Ｂの間に微小な定電流を印加する定電流電源２と、
第１電極Ａの電位が入力される第１電圧フォロワ回路ＶＦ１と、
第１電圧フォロワ回路ＶＦ１の出力ノードＮ１の電位が入力される減算回路３と、
減算回路３の出力ノードＮ２の電位が入力される平滑回路４と、
平滑回路４の出力ノードＮ３の電位が入力される加算回路５と、
電解液１に浸けられた付加電極Ｃと、
付加電極Ｃの電位が入力される第２電圧フォロワ回路ＶＦ２と
を備えて構成されている。 FIG. 1 is a schematic configuration diagram showing a stabilized reference electrode circuit according to an embodiment of the present invention. The stabilized reference electrode circuit is
A first electrode (cathode) A and a second electrode (anode) B which are immersed in the electrolytic solution 1 and constitute the dynamic hydrogen electrode DHE;
A constant current power source 2 that applies a minute constant current between the first and second electrodes A and B;
A first voltage follower circuit VF1 to which the potential of the first electrode A is input;
A subtraction circuit 3 to which the potential of the output node N1 of the first voltage follower circuit VF1 is input;
A smoothing circuit 4 to which the potential of the output node N2 of the subtraction circuit 3 is input;
An adder circuit 5 to which the potential of the output node N3 of the smoothing circuit 4 is input;
An additional electrode C immersed in the electrolytic solution 1;
And a second voltage follower circuit VF2 to which the potential of the additional electrode C is input.

第２電圧フォロワ回路ＶＦ２の出力ノードＮ４の電位は、減算回路３及び加算回路５に入力される。そして、減算回路３は入力される２つの電位の差を出力し、加算回路５は入力される２つの電位の和を出力端子Ｔから出力する。平滑回路４は、入力される電位の波形を平滑して出力する。   The potential of the output node N4 of the second voltage follower circuit VF2 is input to the subtraction circuit 3 and the addition circuit 5. The subtraction circuit 3 outputs the difference between the two input potentials, and the addition circuit 5 outputs the sum of the two input potentials from the output terminal T. The smoothing circuit 4 smoothes and outputs the waveform of the input potential.

図１において、第１及び第２電圧フォロワ回路ＶＦ１、ＶＦ２は、公知の電圧フォロワ回路およびアンプ（例えば等倍アンプ）で構成され、出力インピーダンスは入力インピーダンスよりも低い。減算回路３は、第１オペアンプＤＡ１とその周囲に接続された複数の抵抗とで構成されている。加算回路５も同様に、第２オペアンプＤＡ２とその周囲に接続された複数の抵抗とで構成されている。平滑回路４は、ローパスフィルタＬＰＦとその周
囲に接続された抵抗およびキャパシタとで構成されている。 In FIG. 1, the first and second voltage follower circuits VF1 and VF2 are configured by a known voltage follower circuit and an amplifier (for example, a 1 × amplifier), and the output impedance is lower than the input impedance. The subtracting circuit 3 is composed of a first operational amplifier DA1 and a plurality of resistors connected around it. Similarly, the adder circuit 5 is composed of a second operational amplifier DA2 and a plurality of resistors connected around it. The smoothing circuit 4 is composed of a low-pass filter LPF and resistors and capacitors connected around it.

なお、電圧フォロワ回路、減算回路、加算回路、平滑回路は、当業者には周知である。また、それらの回路を構成するための半導体素子（ＩＣチップ）が種々提供されており、当業者であれば、要求される特性に応じて、それらの中から適宜選択し、選択された半導体素子に応じて、周囲に接続する素子（抵抗、キャパシタ）を適宜設計することも可能である。従って、ここでは、これらの回路の詳細説明を省略する。   Note that the voltage follower circuit, subtraction circuit, addition circuit, and smoothing circuit are well known to those skilled in the art. In addition, various semiconductor elements (IC chips) for configuring these circuits are provided, and those skilled in the art can appropriately select from these according to required characteristics and select the selected semiconductor elements. In accordance with the above, it is possible to appropriately design elements (resistors, capacitors) connected to the periphery. Therefore, detailed description of these circuits is omitted here.

また、図１においては、電気化学装置を構成する作用極Ｄと、対極Ｅと、電源装置６とを示している。作用極Ｄおよび対極Ｅの材料、形状および寸法、並びに、電源装置（ポテンショスタットやガルバノスタットなど）６の仕様は、目的とする電気化学実験に応じて適宜選択することができる。   Further, FIG. 1 shows a working electrode D, a counter electrode E, and a power supply device 6 constituting the electrochemical device. The materials, shapes and dimensions of the working electrode D and the counter electrode E, and the specifications of the power supply device (potentiostat, galvanostat, etc.) 6 can be appropriately selected according to the target electrochemical experiment.

以下に、図１に示した安定化参照電極回路の動作をより具体的に説明する。なお、通常、電気化学実験に用いる電源装置（ポテンショスタットやガルバノスタット）では、作用極がアース（基準電位）になるように回路が設計されている（図１参照）。従って、本安定化参照電極回路を商用電源で駆動する場合（電源装置６のアースと、安定化参照電極回路のアースとを完全に絶縁し、安定化参照電極回路を“浮いた”状態で使わない限り）、この事情を考慮する必要がある。よって、本来であれば電解液の電位を基準として説明すれば理解が容易であるが、以下では、あえて作用極の電位を基準とし、図２に示した電位波形を参照しながら説明する。   Hereinafter, the operation of the stabilized reference electrode circuit shown in FIG. 1 will be described more specifically. Normally, in a power supply device (potentiostat or galvanostat) used for an electrochemical experiment, a circuit is designed so that the working electrode becomes ground (reference potential) (see FIG. 1). Therefore, when this stabilized reference electrode circuit is driven by a commercial power supply (the ground of the power supply 6 and the ground of the stabilized reference electrode circuit are completely insulated, and the stabilized reference electrode circuit is used in a “floating” state. Unless otherwise) this need to be taken into account. Therefore, it is easy to understand if the potential of the electrolytic solution is used as a standard, but the following description will be made with reference to the potential waveform shown in FIG.

図２において、電位Ｅ０は、アースされた基準電位である作用極Ｄの電位を表す。電気化学反応を行なう実験者は、電源装置６を操作し、任意の作用極／電解液電位差を作り出す。それが、電解液１の電位Ｅ１の変化として現れる。図２では、一例として、一定の値から一旦減少し、その後増加して一定の値になる変化として示されている。 In FIG. 2, the potential E 0 represents the potential of the working electrode D, which is a grounded reference potential. An experimenter performing an electrochemical reaction operates the power supply device 6 to create an arbitrary working electrode / electrolyte potential difference. This appears as a change in the potential E 1 of the electrolytic solution 1. In FIG. 2, as an example, it is shown as a change that once decreases from a certain value and then increases to a certain value.

［発明が解決しようとする課題］の項において説明したように、この電解液電位Ｅ１の変化を捉えるための参照極である第１電極Ａの電位ＥＡは、本来、電解液１の電位Ｅ１の変化に追随して平行に変化することが望ましいが、実際には図２に示したように、微小な電位ゆらぎが加算されて出力される。 As described in the section [Invention Problems to be Solved], the potential E A of the first electrode A is a reference electrode for capturing the change in electrolytic solution potential E 1 is essentially of the electrolyte 1 potential it is desirable to vary in parallel to follow the change of E 1, as actually shown in FIG. 2, the minute potential fluctuations is output are added.

一方、不活性だが面積の大きな付加電極Ｃが電解液１に浸けられていると、付加電極Ｃと電解液１の電位との差は不定ではあるが、付加電極Ｃの電位ＥＣは、ある程度の時間範囲で安定になると考えられる。 On the other hand, when the additional electrode C that is inactive but has a large area is immersed in the electrolytic solution 1, the difference between the potential of the additional electrode C and the electrolytic solution 1 is indefinite, but the potential E C of the additional electrode C is somewhat It is thought that it becomes stable in the time range.

従って、本安定化参照電極回路では、第１電極（ＤＨＥ）Ａの電位ＥＡおよび付加電極Ｃの電位ＥＣを、出力インピーダンスが小さい第１及び第２電圧フォロワ回路ＶＦ１、ＶＦ２を介して電位ＥＡ’、ＥＣ’として出力し、測定により電極系が乱されることを防止する。 Accordingly, in the present stabilizing the reference electrode circuit, a potential E C potentials E A and the additional electrode C of the first electrode (DHE) A, through the first and second voltage output impedance is small follower circuit VF1, VF2 potential Output as E A ′ and E C ′ to prevent the electrode system from being disturbed by the measurement.

第１及び第２電圧フォロワ回路ＶＦ１、ＶＦ２の出力ＥＡ’、ＥＣ’は、減算回路３に入力され、減算回路３はそれらの差ＥＡ’−ＥＣ’を出力する。 The outputs E A ′ and E C ′ of the first and second voltage follower circuits VF1 and VF2 are input to the subtraction circuit 3, and the subtraction circuit 3 outputs the difference E A ′ −E C ′.

減算回路３からの電位差ＥＡ’−ＥＣ’は、平滑回路４に入力され、所定の時定数（例えば数十秒）に設計されたローパスフィルタＬＰＦによって比較的低周波数の信号成分が出力される。その結果、入力信号（電位差ＥＡ’−ＥＣ’）から高周波数成分が除去され、入力信号が平滑されることになる。平滑回路４からの出力信号をＥＬＰＦと表す。図１のローパスフィルタＬＰＦでは、入出力信号の極性が反転するので、ＥＬＰＦ＝−（ＥＡ”−ＥＣ”）である。ここで、ＥＡ”およびＥＣ”はそれぞれ、ＥＡ’およびＥＣ’が平
滑回路４によって平滑された信号を表す。 The potential difference E A ′ −E C ′ from the subtraction circuit 3 is input to the smoothing circuit 4 and a signal component having a relatively low frequency is output by a low-pass filter LPF designed to have a predetermined time constant (for example, several tens of seconds). The As a result, the high frequency component is removed from the input signal (potential difference E A '-E C '), and the input signal is smoothed. The output signal from the smoothing circuit 4 is represented as E LPF . In the low pass filter LPF of FIG. 1, since the polarity of the input / output signal is inverted, E LPF = − (E A ″ −E C ″). Here, E A ″ and E C ″ represent signals obtained by smoothing E A ′ and E C ′ by the smoothing circuit 4, respectively.

最後に、平滑回路４からの出力信号ＥＬＰＦ、および、基準として使用される付加極Ｃの電位ＥＣ’（第２電圧フォロワ回路ＶＦ２の出力電位）は加算回路５に入力され、加算されて出力される。図１では、ローパスフィルタＬＰＦの入出力信号の極性が反転するので、加算回路５には減算回路３と同じ回路を用いている。 Finally, the output signal E LPF from the smoothing circuit 4 and the potential E C ′ of the additional pole C used as a reference (the output potential of the second voltage follower circuit VF2) are input to the adding circuit 5 and added. Is output. In FIG. 1, since the polarity of the input / output signal of the low-pass filter LPF is inverted, the same circuit as the subtraction circuit 3 is used for the addition circuit 5.

加算回路５からの出力信号はＥＣ’−ＥＬＰＦであり、上記の関係を考慮すると、ＥＣ’−ＥＬＰＦ＝ＥＣ’＋（ＥＡ”−ＥＣ”）となる。ここで、ＥＣ”はＥＣ’が平滑回路４によって平滑された信号であるが、上記したように不活性だが面積の大きな付加電極Ｃを使用すれば、付加電極Ｃの電位ＥＣは高周波成分を含まないので、電位ＥＣ’も高周波成分を含まない。よって、電位ＥＣ’は平滑回路４を通過しても変化せず、ＥＣ”＝ＥＣ’であり、ＥＣ’＋（ＥＡ”−ＥＣ”）＝ＥＡ”となる。このように、本安定化参照電極回路は、第１電極Ａの電位ＥＡを平滑し、微小な電位ゆらぎが除去された電位ＥＡ”を端子Ｔから供給することができる。 The output signal from the adder circuit 5 is E C '-E LPF , and considering the above relationship, E C ' -E LPF = E C '+ (E A "-E C "). Here, E C ″ is a signal obtained by smoothing E C ′ by the smoothing circuit 4. However, as described above, if the additional electrode C which is inactive but has a large area is used, the potential E C of the additional electrode C is high frequency. does not contain a component, potential E C 'also do not contain high frequency components. Therefore, the potential E C' does not change even after passing through the smoothing circuit 4, E C "= E C ' is, E C' + the (E a "-E C") = E a ". Thus, the stabilized reference electrode circuit, a potential E a of the first electrode a smoothing, fine potential fluctuations removed potential E A ″ can be supplied from terminal T.

上記では、加算回路５として、減算回路３と同じ回路を使用する場合を説明したが、平滑回路４として、入出力信号の極性が反転しない回路を使用する場合には、入力信号を加算して出力する本来の意味の加算回路を使用すればよい。その場合、平滑回路の出力信号は、ＥＡ”−ＥＣ”であり、加算回路の出力は、ＥＡ”−ＥＣ”＋ＥＣ’となる。従って、ＥＣ”＝ＥＣ’を考慮すると、出力端子Ｔから出力される電位は、上記と同様にＥＡ”となる。 In the above, the case where the same circuit as the subtraction circuit 3 is used as the addition circuit 5 has been described. However, when a circuit whose polarity of the input / output signal is not inverted is used as the smoothing circuit 4, the input signal is added. It is only necessary to use an original adder circuit for output. In that case, the output signal of the smoothing circuit is E A "-E C ", and the output of the adder circuit is E A "-E C " + E C '. Therefore, considering E C ″ = E C ′, the potential output from the output terminal T is E A ″ as described above.

また、電圧フォロワ回路、減算回路、平滑回路、加算回路は、増幅率も含めて、必要となる特性を満たすように適宜設計すればよい。また、これらの回路として、入力信号の極性と出力信号の極性とが反転する回路を使用する場合には、反転された信号をさらに反転させる回路（インバータ）を備えて構成すればよい。   In addition, the voltage follower circuit, the subtraction circuit, the smoothing circuit, and the addition circuit may be appropriately designed so as to satisfy necessary characteristics including the amplification factor. Further, as these circuits, when a circuit in which the polarity of the input signal and the polarity of the output signal are inverted is used, a circuit (inverter) that further inverts the inverted signal may be provided.

また、平滑回路の時定数は、これに限定されないが、約１０秒以上であることが望ましい。より望ましくは約２０秒〜１００秒であればよい。   The time constant of the smoothing circuit is not limited to this, but is preferably about 10 seconds or longer. More desirably, it may be about 20 seconds to 100 seconds.

また、付加電極は、これに限定されないが、縦約１０〜１００ｍｍ、横約２〜２０ｍｍ、厚さ約０．１〜１ｍｍの直方体（板状体）であることが望ましい。材質は、導電性材料であればよいが、カーボン、金などであることが望ましく、また、有効表面積を増加させる観点から表面が粗化されたもの、あるいは多孔質体であることが望ましい。   Moreover, although an additional electrode is not limited to this, It is desirable that it is a rectangular parallelepiped (plate-shaped body) of about 10-100 mm in length, about 2-20 mm in width, and about 0.1-1 mm in thickness. The material may be any conductive material, but is preferably carbon, gold, or the like, and is preferably a material whose surface is roughened or a porous body from the viewpoint of increasing the effective surface area.

以下に実施例を示し、本発明の特徴とするところをより一層明確にする。   Examples are shown below to further clarify the features of the present invention.

ＤＨＥを参照極として、代表的な電気化学測定であるサイクリックボルタンメトリー（作用極の保持電位を三角波状に変化させる実験）を行い、その際に作用極の電位が正しく三角波状に制御できているかどうかを第二の参照極（検証用参照極）を付加的に用いて検証した。   Cyclic voltammetry (experiment that changes the holding potential of the working electrode in a triangular waveform) is performed using DHE as a reference electrode, and whether the potential of the working electrode is correctly controlled in a triangular waveform. It was verified by additionally using a second reference electrode (reference electrode for verification).

平滑回路の使用の有効性を検証するには、ＤＨＥがある程度不安定な条件下で実験する必要があるが、検証用参照極は安定な電位を示す必要がある。そこで、電極および電解液は通常使用されるものを選択した。その上で、ＤＨＥには故意にノイズを与える実験を試みた。   In order to verify the effectiveness of the use of the smoothing circuit, it is necessary to perform an experiment under a condition where DHE is unstable to some extent, but the verification reference electrode needs to exhibit a stable potential. Therefore, electrodes and electrolytes that are usually used were selected. Based on this, an experiment was made to intentionally give noise to DHE.

図３、図４に実験に用いた２つの構成を示す。図３は、平滑回路を用いず、ＤＨＥ単独
を参照極として用いた構成を示す。ポテンショスタットの参照極端子にはＤＨＥの陰極をそのまま入力した。これに対して、図４は、平滑回路を用いた構成を示しており、本発明である安定化参照電極回路の出力をポテンショスタットの参照極端子に入力している。 3 and 4 show two configurations used in the experiment. FIG. 3 shows a configuration in which DHE alone is used as a reference electrode without using a smoothing circuit. The DHE cathode was directly input to the reference electrode terminal of the potentiostat. On the other hand, FIG. 4 shows a configuration using a smoothing circuit, and the output of the stabilized reference electrode circuit according to the present invention is input to the reference electrode terminal of the potentiostat.

電解液には０．５ｍｏｌ／Ｌの硫酸水溶液を用い、対極には白金板を、作用極には白金線を用い、検証用参照極としては、水溶液系で広く用いられている銀／塩化銀電極を用いた。ＤＨＥは本来定電流で運転するものであるが、故意に設定電流を周期的に変動させて、「不安定条件下のＤＨＥ」を模した。具体的には、電流を、５μＡと６．５μＡとの間で約０．１Ｈｚの変化速度で往復させた。   A 0.5 mol / L sulfuric acid aqueous solution is used for the electrolyte, a platinum plate is used for the counter electrode, a platinum wire is used for the working electrode, and a silver / silver chloride widely used in aqueous solutions as a reference electrode for verification. An electrode was used. DHE originally operates at a constant current, but the set current was intentionally varied periodically to simulate “DHE under unstable conditions”. Specifically, the current was reciprocated between 5 μA and 6.5 μA at a change rate of about 0.1 Hz.

平滑回路の電圧基準となる「付加極」には大面積（縦２０ｍｍ、横１０ｍｍ）の多孔質カーボン電極を用いた。平滑回路の時定数は１００秒に設定した。ポテンショスタットの設定電位は、０．２Ｖの走査幅内を２ｍＶ／ｓの走査速度で三角波状に上下変化させた。このサイクリックボルタンメトリー実験を行なっている間、検証用参照極（銀／塩化銀電極）に対する作用極（白金線）の電位を電圧計記録計で記録した。   A porous carbon electrode having a large area (vertical 20 mm, horizontal 10 mm) was used as the “additional electrode” serving as a voltage reference for the smoothing circuit. The time constant of the smoothing circuit was set to 100 seconds. The set potential of the potentiostat was changed up and down like a triangular wave at a scanning speed of 2 mV / s within a scanning width of 0.2V. During this cyclic voltammetry experiment, the potential of the working electrode (platinum wire) with respect to the reference electrode for verification (silver / silver chloride electrode) was recorded with a voltmeter recorder.

実験結果として、図５に検証用参照極（銀／塩化銀電極）を用いて測定した作用極電位の経時変化を示す。太い実線は図３の構成での測定結果であり、細い実線は図４の構成での実験結果である。図５から次のことが検証された。   As an experimental result, FIG. 5 shows a change with time of the working electrode potential measured using the reference electrode for verification (silver / silver chloride electrode). The thick solid line is the measurement result in the configuration of FIG. 3, and the thin solid line is the experimental result in the configuration of FIG. The following was verified from FIG.

ＤＨＥ単独の場合（図３の構成）、故意に設定電流を撹乱させていることに伴うＤＨＥ電位の変動が作用極の電位変動として現れている。一方、安定化参照電極回路を使用した場合（図４の構成）、平滑回路の時定数（１００秒）が撹乱の周期（約１０秒）よりも充分に大きいため、ＤＨＥの電位変動が作用極の電位変動を引き起こさなくなっている（楕円領域参照）。さらに、本回路の特徴である「付加極を基準としての平滑化」の効果により、電気化学測定実験者が本来意図している電位変化（本実験の場合三角波の折り返し時など）は正しく実現されている（円領域参照）。   In the case of DHE alone (configuration in FIG. 3), the fluctuation of the DHE potential caused by intentionally disturbing the set current appears as the potential fluctuation of the working electrode. On the other hand, when the stabilized reference electrode circuit is used (configuration shown in FIG. 4), the time constant (100 seconds) of the smoothing circuit is sufficiently larger than the disturbance period (about 10 seconds), so that the DHE potential fluctuation is the working electrode. (See the elliptical area). In addition, due to the effect of “smoothing with the additional pole as a reference”, which is a feature of this circuit, the potential change that the electrochemical measurement experimenter originally intended (in the case of this experiment, such as when the triangular wave is folded) is correctly realized. (See circle area).

１ 電解液
２ 定電流電源
３ 減算回路
４ 平滑回路
５ 加算回路
６ 電源装置
Ａ 第１電極（陰極）
Ｂ 第２電極（陽極）
Ｃ 付加電極
Ｄ 作用極
Ｅ 対極
ＶＦ１、ＶＦ２ 第１及び第２電圧フォロワ回路
ＤＡ１、ＤＡ２ 第１及び第２オペアンプ
Ｎ１〜Ｎ４ 第１〜第２ノード
ＬＰＦ ローパスフィルタ DESCRIPTION OF SYMBOLS 1 Electrolyte 2 Constant current power supply 3 Subtraction circuit 4 Smoothing circuit 5 Addition circuit 6 Power supply device A 1st electrode (cathode)
B Second electrode (anode)
C additional electrode D working electrode E counter electrode VF1, VF2 first and second voltage follower circuits DA1, DA2 first and second operational amplifiers N1-N4 first-second node LPF low-pass filter

Claims (4)

動的水素電極を用いた安定化参照電極回路であって、
電解液に浸けられ、前記動的水素電極の陰極である第１電極及び前記動的水素電極の陽極である第２電極と、
前記第１及び第２電極の間に定電流を印加する定電流電源と、
前記第１電極の電位が入力される第１電圧フォロワ回路と、
前記電解液に浸けられた付加電極と、
前記付加電極の電位が入力される第２電圧フォロワ回路と
前記第１及び第２電圧フォロワ回路の出力電位が入力される減算回路と
前記減算回路の出力電位が入力される平滑回路と、
前記平滑回路及び前記第２電圧フォロワ回路の出力電位が入力される加算回路とを備え、
前記減算回路が、入力される前記第１電圧フォロワ回路の出力電位から前記第２電圧フォロワ回路の出力電位を減算した電位を出力し、
前記平滑回路が、前記減算回路の出力電位を平滑して出力し、
前記加算回路が、前記平滑回路及び前記第２電圧フォロワ回路の出力電位を加算して出力することを特徴とする安定化参照電極回路。 A stabilized reference electrode circuit using a dynamic hydrogen electrode,
A first electrode that is immersed in an electrolyte and is a cathode of the dynamic hydrogen electrode; and a second electrode that is an anode of the dynamic hydrogen electrode;
A constant current power source for applying a constant current between the first and second electrodes;
A first voltage follower circuit to which the potential of the first electrode is input;
An additional electrode immersed in the electrolyte;
A second voltage follower circuit to which the potential of the additional electrode is input; a subtraction circuit to which the output potential of the first and second voltage follower circuits is input; and a smoothing circuit to which the output potential of the subtraction circuit is input;
An addition circuit to which an output potential of the smoothing circuit and the second voltage follower circuit is input;
The subtracting circuit outputs a potential obtained by subtracting the output potential of the second voltage follower circuit from the output potential of the first voltage follower circuit;
The smoothing circuit smoothes and outputs the output potential of the subtraction circuit;
The stabilized reference electrode circuit, wherein the adding circuit adds and outputs the output potentials of the smoothing circuit and the second voltage follower circuit. 動的水素電極を用いた安定化参照電極回路であって、
電解液に浸けられ、前記動的水素電極の陰極である第１電極及び前記動的水素電極の陽極である第２電極と、
前記第１及び第２電極の間に定電流を印加する定電流電源と、
前記第１電極の電位が入力される第１電圧フォロワ回路と、
前記電解液に浸けられた付加電極と、
前記付加電極の電位が入力される第２電圧フォロワ回路と
前記第１及び第２電圧フォロワ回路の出力電位が入力される第１減算回路と
前記第１減算回路の出力電位が入力される平滑回路と、
前記平滑回路及び前記第２電圧フォロワ回路の出力電位が入力される第２減算回路とを備え、
前記第１減算回路が、入力される前記第１電圧フォロワ回路の出力電位から前記第２電圧フォロワ回路の出力電位を減算した電位を出力し、
前記平滑回路が、前記第１減算回路の出力電位を平滑し、且つ極性を反転させて出力し、
前記第２減算回路が、前記第２電圧フォロワ回路の出力電位から、前記平滑回路の出力電位を減算して出力することを特徴とする安定化参照電極回路。 A stabilized reference electrode circuit using a dynamic hydrogen electrode,
A first electrode that is immersed in an electrolyte and is a cathode of the dynamic hydrogen electrode; and a second electrode that is an anode of the dynamic hydrogen electrode;
A constant current power source for applying a constant current between the first and second electrodes;
A first voltage follower circuit to which the potential of the first electrode is input;
An additional electrode immersed in the electrolyte;
A second voltage follower circuit to which the potential of the additional electrode is input; a first subtraction circuit to which the output potential of the first and second voltage follower circuits is input; and a smoothing circuit to which the output potential of the first subtraction circuit is input When,
A second subtraction circuit to which an output potential of the smoothing circuit and the second voltage follower circuit is input;
The first subtraction circuit outputs a potential obtained by subtracting the output potential of the second voltage follower circuit from the output potential of the first voltage follower circuit;
The smoothing circuit smoothes the output potential of the first subtracting circuit and inverts and outputs the polarity;
The stabilized reference electrode circuit, wherein the second subtraction circuit subtracts an output potential of the smoothing circuit from an output potential of the second voltage follower circuit. 前記平滑回路の時定数が、２０秒以上１００秒以下であることを特徴とする請求項１又は２に記載の安定化参照電極回路。   3. The stabilized reference electrode circuit according to claim 1, wherein a time constant of the smoothing circuit is 20 seconds or more and 100 seconds or less. 前記付加電極が、縦１０ｍｍ以上１００ｍｍ以下、横２ｍｍ以上２０ｍｍ以下の板状体であり、カーボンで形成されていることを特徴とする請求項１〜３の何れか１項に記載の安定化参照電極回路。   The stabilization reference according to any one of claims 1 to 3, wherein the additional electrode is a plate-like body having a length of 10 mm to 100 mm and a width of 2 mm to 20 mm, and is formed of carbon. Electrode circuit.
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