| Hydrogen production by electrolysis is an effective way to convert the intermittent and unstable energy obtained from large scale solar and wind energy to the green hydrogen energy.It can provide efficient and rapid hydrogen production methods for the future hydrogen energy.Compared with traditional electrolysis of water,the electrolysis of carbonate solution can not only produce hydrogen and oxygen,but also obtain NaOH and NaHC03/C02 products,which have broad prospects of application in the chemical processes of membrane electrolysis-alkaline digestion&carbonation precipitation for production of alumina,recycling of alkaline C02 absorbent and electrochemical reduction of C02.However,the kinetic performance of oxygen evolution in carbonate solution is poor,and thus resulting in highenergy consumption of electrolysis.Moreover,the acidification of the solution during the electrolysis will cause serious corrosion of the catalyst.In order to solve the above problems,this paper proposes to prepare highly effective corrosion resistant nickel iron chromium complex hydroxide by electrodeposition method as oxygen evolution catalyst in carbonate solution.The main contents of this paper are as follows:1.NiFeCr(OH)x/SLS and NiFeCr(OH)x/NF were prepared on stainless steel(SLS)or foam nickel(NF)substrates by co-electrodeposition.The influence of the preparation conditions such as the concentration of Ni/Fe/Cr metal ion,the deposition current density and the deposition time on the properties of the materials were investigated.The experimental results show that the anodic oxygen evolution performance of the prepared SLS is the best when the deposition time is 600 s and the deposition current density is 50 mA·cm-2.When NF was used as the substrate,the optimum codeposition current density and time were 200 mA-cm-2 and 120 s,respectively.The oxygen evolution overpotential ?10 and ?100 of the prepared electrode are 430 mV and 650 mV in 0.5 mol L-1 Na2CO3/NaHCO3 solution respectively,and the oxygen evolution overpotential is the smallest.2.NiFe(OH)x@Cr(OH)3/SLS and NiFe(OH)x@Cr(OH)3/NF oxygen evolution anodes were prepared by a stepwise deposition of chromium hydroxide at the first deposition of nickel iron hydroxide.The results of SEM and XPS show that the structure of the surface of stainless steel mesh and the surface of nickel foam is made of irregular stacked spheres composed of interconnected ultra-thin nanoscale,and the surface oxides are composed of NiFe(OH)x thin slices and Cr(OH)3 grains.The electrochemical performance analysis shows that the NiFeCr(OH)x/SLS and NiFeCr(OH)x/NF electrodes prepared with the deposition current density of 200 mA·cm-2 and the deposition time of 60 s have the best catalytic performance for oxygen evolution,and the deposition effect based on NF is better than that of the SLS substrate.3.The oxygen evolution activity and stability of the electrode prepared by the step-by-step electrodeposition method are better than the co-electrodeposition method.LSV test results showe that in 0.5 mol L-1 Na2C03/NaHC03 solution,the Tafel slope of NiFe(OH)x@Cr(OH)3/NF electrode prepared by step electrodeposition is 33 mV dec-1.The oxygen evolution overpotential at 10 mA·cm-2 is only 370 mV,which is 60 mV lower than that of NiFeCr(OH)x/NF electrode prepared by co-deposition.From the test results of stability,it can be seen that the NiFe(OH)x@Cr(OH)3/NF electrode prepared by stepwise electrodeposition in carbonate solution has the best stability.The polarization potential remains stable for 98 h at current density of 10 mA-cm-2. |
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