Electrocatalytic Oer Activity Of Co-Fe LDH In Neutral And Near Neutral Aqueous Solution

At present,efficient splitting of water into hydrogen and oxygen as an effective way to achieve solar and wind energy storage,and thus become an solution to the energy crisis and environmental problems.The oxygen evolution reaction(OER)is a major bottleneck in water splitting because it involves four electron and proton transfer steps.Electrocatalytic water oxidation via the introduction of precious and non-precious metal catalysts has been demonstrated to be a feasible method for improving OER activity.However,most noble and non-noble metal catalysts are mainly used in acidic and alkaline media,and they are low energy transfer in neutral media especially neutral non-buffering sea water.The direct use of sea water instead of high pure water is of great importance because 97%of the total water available on the planet is salt water.However,the catalyst has two major problems to OER in neutral medium.On the one hand,the catalyst has high OER onset potential and low current density in neutral solution.On the other hand,there is a strong dependence on buffer electrolytes in neutral solution and the catalyst is easily deactivated during the long-term testing process and competition from chloride oxidation reactions in sea water.Therefore,it is very important to reduce the onset potential of OER,improve the current density,and effectively prevent the deactivation of the catalyst and competition from chloride oxidation reactions in the neutral medium.In this paper,Co-Fe LDH with layered structure and interlayer anion exchangeable was prepared by the separate nucleation and aging steps method.It was applied to neutral non-buffered sea water and PBS,and study the catalyst reaction mechanism and influencing factors in neutral media.The main results of the experiments are present as follows:1.Co-Fe LDH as a catalyst was prepared by the separate nucleation and aging steps method,the neutral non-buffer solution was prepared by using sea salt as the electrolyte.Its electrocatalytic oxygen evolution performance was studied.The experimental data show that the catalyst exhibits a large OER current density in sea water and good long-term performance and stability by controlled potential electrolysis.The current density remained approximately 86%of the original value after 8 h at constant overpotential of 560 mV and a current density of～10.4 mA/cm2 was attained.The value is matched to the 10-20 mA/cm2 output of a commercial photovoltaic device.And we have explored the reasons for the excellent electrochemical performance of the catalyst in sea water and found that the anions and cation in the electrolyte solution had an important contribution to the improvement of the catalyst activity.This study will provide the possibility for the direct application of Co-Fe LDH to the electrolysis of near neutral natural sea water,and provide more design ideas for improving the electrochemical performance of the catalyst in neutral systems.2.Co-Fe LDH by electrochemical reduction for half an hour was used as catalyst and studied the OER performance of catalyst in neutral buffer solution PBS.The experimental results show that the OER onset potential is reduced by 100 mV after electrochemical reduction treatment,and the current density is also increased.The reason may be attributed to that electrochemical treatment changes the valence of metals Co and Fe,thereby promoting the conduct of OER reactions.At the same time the process is also the crystallization of the crystal to the amorphous transition by above measured,which also improve the electrochemical activity also has a certain contribution.It can be seen that the metal valence of OER catalyst is also one of the measures to improve its electrocatalytic activity.