Study On Electrolytic Water Properties Of Co-MOFs Nanosheets And Their Derivatives

In recent years,the energy issue has been one of the biggest problems facing human survival and development.The sharp increase in energy demand and the sharp decline in energy resources have become one of the main contradictions in the human development process.Hydrogen energy is recognized as an alternative clean energy source due to its cleanliness and regenerability.However,the preparation of hydrogen has always been an industrial difficulty.Water decomposition is widely recognized as a promising strategy for renewable,clean and efficient energy production.Among them,electrochemical total water decomposition is one of many methods of decomposing water.It is driven by two half-cell reactions,including a hydrogen evolution reaction（HER）and an oxygen release reaction（OER）.However,the electrolysis efficiency in the HER and OER processes is very low due to the inevitable dynamic overpotential.Therefore,exploring efficient electrolyzed water catalysts has become a hot spot.Based on the theoretical basis,this paper designs and synthesizes high-efficiency catalysts based on metal-organic framework materials and studies their applications in the field of electrocatalytic total decomposition water.main tasks as follows:（1）A flaky cobalt-based metal organic framework material was constructed by chemical deposition method,and its catalytic performance in oxygen evolution reaction（OER）was studied.The results show that this catalyst exhibits superior OER catalytic activity and HER properties are not satisfactory.At a low current density of10 mA·cm^-2,the overpotential of the catalyst is only 188 mV with a small impedance.On this basis,two schemes were designed to modify the materials to improve the total decomposition efficiency.（2）Co-MOF is deposited on the current collector foam by chemical precipitation,and then the iron element is introduced into the metal organic framework by a displacement reaction to form a composite,which is converted into a double metal phosphide at a low temperature phosphating.The decomposition water experiment confirmed that the two metals played a certain synergistic role in the catalysis after the introduction of Fe element,which not only had a good catalytic effect on the oxygen evolution reaction,but also greatly improved the hydrogen evolution reaction efficiency.At a current density of 50 mA·cm^-2,the OER overpotential is 278 mV,the HER overpotential is 136 mV,and the potential required for total decomposition of water is only 1.65 V.（3）It is known in experiments and literature reports that the double metal hydroxide has good OER catalytic activity,but the catalytic activity for HER is generally not high,so a rational design based on this design is used to improve this situation.First,hydrothermal method is to co-grow two kinds of transition metal elements,iron and nickel,onto the foamed nickel to form a double metal hydroxide nanosheet,and then deposit the Co-MOF nanosheet onto the hydroxide sheet by chemical deposition to form a composite.Finally,a low-efficiency phosphating treatment was used to prepare a highly efficient total decomposition water catalyst.The catalyst has an OER overpotential of only 230 mV at 100 mA·cm^-2 and HER overpotential of only 154 mV.The potential required for total decomposition of water is only 1.65 V.Experiments have confirmed that this design can be used as an effective alternative to alleviating the tension caused by clean energy fossil fuels.