A kind of metal anode that is used for the aqueous electrolysis system
Technical field
The invention belongs to the aqueous electrolysis field, relate to a kind of oxygen electrode of analysing, particularly porous metal electrode, utilize its high-specific surface area to reduce oxygen evolution potential.
Background technology
The theoretical electrolysis voltage that brine electrolysis is produced hydrogen and oxygen is 1.23V, but in fact, because overpotential, bath resistance and other resistance factor in oxygen and the hydrogen formation reaction process, it is high that the voltage ratio theoretical value of actual needs is wanted, between 1.65-2.4V.The existence of overpotential has increased the brine electrolysis energy consumption, according to Faraday's law, produces 1m
3(standard) hydrogen, theoretical power consumption is 2.87kWh, and actual electric weight is 2 times of theoretical power consumption.Therefore, should manage to reduce the electrode overpotential, to reduce the brine electrolysis energy consumption.
Electrolytic process in alkaline aqueous solution, higher overpotential for oxygen evolution are the major causes that causes high energy consumption.The method that reduces overpotential for oxygen evolution at present mainly contains following three kinds: (1) improves reacting liquid temperature; (2) increase electrode area; (3) apply high activated catalyst at electrode surface.Improve reacting liquid temperature for water solution system, the boiling point of water is the limit, and the pressurization that continues to heat will further increase cost.The development work of high activated catalyst is the research focus always, but catalyzer is in the load of electrode surface and solution not yet in effect, and the catalyzer obscission is serious.Thereby can reduce current density reduction overpotential for oxygen evolution though increase electrode area, the simple electrode size that increases can make the electrolyzer cost of investment increase greatly.
In addition, the novel process of aqueous electrolysis industry has proposed new requirement to analysing oxygen electrode.Proposed to improve the novel process that alumina producing efficient can realize the recycle of alkali lye again in the Chinese invention patent " a kind of technology of producing aluminum oxide by alkali dissolving carbonation method (application number 200710178670.2) ".The electrolytic carbon acid sodium solution prepares sodium hydroxide solution and sodium hydrogen carbonate solution is the key point of whole process flow in this technology.The anode of this electrowinning process is analysed oxygen, and cathode hydrogen evolution, the bath voltage during work are produced required power consumption than higher up to 2.5-2.9V.Therefore, under the condition of operating device cost of investment, effectively reduce the electrowinning process bath voltage, this technology is realized that industrialization is significant.
Summary of the invention
According to Ta Feier equation η=a+blgi, wherein a and b are positive number.When electrode active material fixedly the time, a, b numerical value are certain.If current density i increases, the then corresponding increase of overpotential η.On the other hand, current density i=I/S, I are strength of current, and S is an electrode area.Hence one can see that, and when the strength of current I of the electrode of flowing through one timing, overpotential η and lgS are inversely proportional to, and promptly increase electrode area S and can reduce overpotential η.That is to say, in the aqueous electrolysis system, under the electrode material condition identical, increase electrode area and can reduce the overpotential η that analyses oxygen electrode, still, increase electrode area merely and can increase equipment investment cost greatly with catalyzer.
At above-mentioned deficiency of the prior art, the present invention proposes the metal anode of the big expanded metal of a kind of specific surface area as anode substrate, load high activated catalyst, to reduce the overpotential for oxygen evolution of aqueous electrolysis system.
The metal anode that is used for the aqueous electrolysis system that the present invention proposes is characterized in that with the porous metal material being matrix, the area load high activated catalyst.
The porous metal electrode that the present invention proposes by the repressed slabbing of spherical or erose metal or alloy powder, is made through sintering again.Material internal has the three-dimensional pore space structure of being made up of micron hole on equally distributed connection macroporosity and the hole wall, volume porosity is 30%~60%, and opening porosity is 60~99.7%, 1~100 micron of mean pore size, Young's modulus is 0.5~37GPa, and ultimate compression strength is 0.04~2.2GPa.
The porous metal electrode that the present invention proposes, its material can be various metal or alloy such as titanium, stainless steel, nickel, copper.Consider from anti-corrosion anodic angle, be advisable with titanium.
The porous metal electrode that the present invention proposes, its surface-coated catalyst layer.Catalyzer is the material that can reduce overpotential for oxygen evolution, for example catalytic removal of nox and other metal oxide.The method that applies can be that presoma is coated in porous metal sheet surface, high temperature sintering again, maybe the catalyzer for preparing is adopted the mode of electrophoretic deposition, or adopts electrochemical method directly synthetic in porous metal sheet surface electrical.
The porous metal electrode that the present invention proposes because its inside has vesicular structure, can effectively increase the electrochemical activity surface-area of electrode, and help supported catalyst, thereby effectively reduce the anodic overpotential for oxygen evolution, realizes energy-saving and cost-reducing purpose.
Embodiment
The invention will be further described below in conjunction with comparative example and embodiment.
Comparative example 1
After alkali cleaning oil removing washing, etching 3h in oxalic acid solution (10%) then is placed in the distilled water standby with netted titanium electrode substrate.With chloro-iridic acid (H
2IrCl
66H
2O, AR, Beijing Non-Fervoous Metal Inst.), propyl carbinol and concentrated hydrochloric acid mix by 1: 10: 1 volume ratio, evenly be coated on the above-mentioned titanium net matrix with soft woollen goods brush pen, dry 10min down in 120 ℃, then at 450 ℃ of predetermined roasting temperature 15min, repetitive coatings-drying-roasting process 4 times promptly makes the titanium base and is coated with the iridium mesh electrode.
With ion-exchange membrane electrolyzer detecting electrode performance, it is anode that this titanium is coated with iridium electrode, and it is negative electrode that nickel is coated with ruthenium electrode, and cationic membrane is a barrier film, and the electrolytic solution of positive column is the Na of 1.5mol/L
2CO
3Solution, the electrolytic solution in cathodic area are the NaOH solution of 6.5mol/L, and cathode and anode spacing is about 4mm, and the electrolytic tank electrode useful area is 120cm
2, electrolysis under 75 ℃ condition is when current density is 1000A/m
2The time average cell voltage be about 2.60V.
Embodiment 1
After alkali cleaning oil removing washing, etching 3h in oxalic acid solution (10%) then is placed in the distilled water standby with powder metallurgy gained titanium plate.With chloro-iridic acid (H
2IrCl
66H
2O, AR, Beijing Non-Fervoous Metal Inst.), propyl carbinol and concentrated hydrochloric acid mix by 1: 10: 1 volume ratio, evenly be coated on the above-mentioned powder metallurgy titanium matrix with soft woollen goods brush pen, dry 10min down in 120 ℃, then at 450 ℃ of predetermined roasting temperature 15min, repetitive coatings-drying-roasting process 4 times promptly makes powder metallurgy titanium base and is coated with iridium electrode.
With ion-exchange membrane electrolyzer detecting electrode performance, it is anode that this powder metallurgy titanium base is coated with iridium electrode, and it is negative electrode that nickel is coated with ruthenium electrode, and cationic membrane is a barrier film, and the electrolytic solution of positive column is the Na of 1.5mol/L
2CO
3Solution, the electrolytic solution in cathodic area are the NaOH solution of 6.5mol/L, and cathode and anode spacing is about 4mm, and the electrolytic tank electrode useful area is 120cm
2, electrolysis under 75 ℃ condition is when current density is 1000A/m
2The time average cell voltage be about 2.52V.
Embodiment 2
After alkali cleaning oil removing washing, etching 3h in oxalic acid solution (10%) then is placed in the distilled water standby with powder metallurgy titanium plate.With hydrate ruthenium trichloride (RuCl
3NH
2O, GR, Shanghai Chemical Reagent Co., Ltd., Sinopharm Group), propyl carbinol and concentrated hydrochloric acid mix by 1: 10: 1 volume ratio, evenly be coated on the above-mentioned Ti mmaterial matrix with soft woollen goods brush pen, dry 10min down in 120 ℃, then at 450 ℃ of predetermined roasting temperature 15min, repetitive coatings-drying-roasting process 4 times promptly makes powder metallurgy titanium base and is coated with ruthenium electrode.
With ion-exchange membrane electrolyzer detecting electrode performance, it is anode that this powder metallurgy titanium base is coated with ruthenium electrode, and it is negative electrode that nickel is coated with ruthenium electrode, and cationic membrane is a barrier film, and the electrolytic solution of positive column is the Na of 1.5mol/L
2CO
3Solution, the electrolytic solution in cathodic area are the NaOH solution of 6.5mol/L, and cathode and anode spacing is about 4mm, and the electrolytic tank electrode useful area is 120cm
2, electrolysis under 75 ℃ condition is when current density is 1000A/m
2The time average cell voltage be about 2.56V.