Preparation Of Transition Metal-based Catalysts And Study On Its Electrochemical Performance

With population growth and economic development,global energy demand is increasing.Fossil fuels such as crude oil,natural gas and coal are the current main sources of energy,and people will still use them to obtain energy for quite a long time.However,these fossil fuel-based energy sources will produce a large number of toxic and harmful polluting gases during use,and CO₂ among them is the"culprit"that causes the greenhouse effect.At the same time,as a non-renewable energy source,fossil fuels will one day face exhaustion that cannot meet human needs.Therefore,there is an urgent need to explore and develop alternative renewable energy sources,among which solar energy,wind energy,water energy and tidal energy are considered promising alternatives.However,intermittent and geographical restrictions require that people must effectively capture,convert,and store these green energy sources in chemical form.Hydrogen?H₂?has been considered as a carrier of green energy because of its high energy density per unit mass and cleanliness during use.In addition,H₂ is also an important chemical raw material for many chemical conversions and ammonia synthesis in the petroleum industry.However,most of the H₂ in the current market is produced by fossil fuels through chemical reactions,which requires a large amount of energy input,and at the same time inevitably leads to the emission of toxic and harmful polluting gases during the reaction.As a result,it pollutes the environment and cannot achieve sustainable and environmental protection.In this case,water electrolysis is considered to be an effective way to produce H₂,and its own clean characteristic in the process of producing H₂ by water electrolysis make it easy to widely used.More importantly,the electrical input for water electrolysis can come directly from renewable energy sources?solar energy,wind energy,water energy,etc.?.Under standard conditions,the thermodynamic potential of water electrolysis to generate H₂ and O₂ is 1.23V.However,since the kinetics of both half reactions are slow,a large overpotential?the difference between the applied potential and the thermodynamic potential?is usually required to achieve an industrially relevant current density,thus resulting in lower energy conversion efficiency.In this regard,people have made tremendous efforts to explore and develop various electrocatalytic systems in order to reduce over-electricity requirements and at the same time improve the overall energy conversion efficiency.The focus is on the development of qualified electrocatalysts.The most advanced H₂ and O₂ evolution reaction?HER and OER?electrocatalysts are Pt and Ir O₂/RuO2,respectively.However,the disadvantages of low content and high price limit their large-scale application.The transition metal-based electrocatalyst has high electrocatalytic activity,rich earth content and low cost,so it can be used for electrochemical water splitting.These electrocatalysts exhibit high HER or high OER activity,and some of them even exceed the performance of benchmark precious metal-based catalysts.In this paper,we have developed transition metal-based electrocatalysts with transition metals as the main line and carbon materials as the substrate,then tested and characterized their electrochemical performance.The carbon material as a substrate can provide a supporting platform,increase the specific surface area of the material,and expose more active sites.At the same time,through doping,we change the atomic structure and properties of the material to improve the electrocatalytic performance of the material.The specific work are as follows:?1?As a noble metal,Ru has good HER catalytic performance,but the price is high.And Cu as a non-noble metal material,has low price but poor conductivity.We doped Ru with Cu to form a RuCu alloy and supported it on a carbon black substrate?CB??RuCu/CB?.Experimental tests show the excellent HER performance of the prepared RuCu/CB electrocatalyst:It has an effective HER catalytic performance in neutral and alkaline electrolyte solutions,requiring only 91 mV and 85 mV overpotentials to provide a release current of 10 mV·cm^-2.The corresponding small Tafel slopesare 46 mV·dec^-11 and 43 mV·dec^-1,respectively,with impressive intrinsic activity and Tafel slope comparable to that of the Pt/C.And after the Ru Cu/CB is tested in 3000 cycles of LSV,the HER performance remains almost unchanged,with long-term stability and durability.?2?Ni₃S₂ has strong hydrogen?H*?adsorption capacity,but has poor H*desorption and H₂ production capacity.Therefore,in order to improve the intrinsic electrocatalytic activity of Ni₃S₂,we selected Al for doping,and formed Al-Ni₃S₂/CFC using carbon fiber material?CFC?as the substrate.Al doping and CFC played an active role,improving the electrocatalytic performance of Al-Ni₃S₂/CFC.The experimental results show that the overpotential of Al-Ni₃S₂/CFC at a current density of 10 mA·cm^-2 is only 1.416 V,and the corresponding small Tafel slope is 140mV·dec^-1.Through CV,it is calculated that it has a large electrochemically active area of 1020 cm².At the same time,the Nernst curve shows that Al-Ni₃S₂/CFC has a small resistance of 12?.The above results indicate that Al-Ni₃S₂/CFC has good electrocatalytic oxygen evolution performance and is an excellent electrocatalytic material.