Desing And Synthesis Of Copper Phosphide-based Nanomaterials And Their Electrocatalysis Performance For Water Splitting

Because traditional energy reserves are limited and a large amount of greenhouse gases are generated when used,the research on clean and renewable energy is of great significance.Hydrogen(H₂)is an ideal new energy material due to its high energy density,and the combustion products are pollution-free.Hydrogen production by electrolysis of water can directly produce high-purity H₂without harmful gas by-products.However,due to the unfavorable factors of its kinetics,high power consumption is usually required.The use of catalysts can reduce unnecessary power consumption in the process of water electrolysis.Pt-based and Ru-based precious metals are the best catalysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),respectively.However,due to their small reserves,high price and poor stability,they cannot be applied in large-scale production.In this paper,the cheap non-noble metal catalyst copper phosphide as the research object,from the morphology,elements,structure and other aspects of its improvement,in order to obtain high activity,high stability,high cost-effective electrolytic water catalyst.The main research contents and results of this paper are as follows:(1)Using phosphorous resin and copper foam(CF)as raw materials,Cu₃P nanosheets coated with nitrogen and phosphorus(N,P)co-doped carbon layer,which were grown in situ on copper foam,were obtained by epitaxial growth method in one step at high temperature(Cu₃P@NPC-CF).The thickness of N,P double-doped carbon shell is about 10 layers(?4 nm),which not only provides abundant active sites,but also endows Cu₃P nanomaterials with strong acid and alkali resistance.The thickness of Cu₃P nanosheets was about 30 nm,the width was more than 3?m,and the width-to-thickness ratio was more than 100,which made the Cu₃P nanosheets exposed more active sites.And due to the effect of no binder,Cu₃P@NPC-CF has a good electron transmission capacity.Then,its electrochemical properties in acidic(0.5 M H₂SO₄),neutral(1 M Phosphate Buffer Solution,PBS)and alkaline(1 M KOH)electrolyte,and Cu₃P@NPC-CF electrocatalyst exhibited excellent HER activity and stability.In acidic,neutral and alkaline solutions,only 81.94,192.52 and 135.45 mV are needed to reach the current density of 10 mA cm^-2,and the Tafel slope is only 81.25,127.71 and 93.14mV dec^-1,respectively.And after 90 hours of stability test,the current retention rate is 81.32%,96.06%,95.61%,with excellent stability.(2)Cu₃P-Cu₂O Janus nanoparticles(the size of particles is about 50 nm)supported on N,P co-doped porous carbon(Cu₃P-Cu₂O/NPC)were successfully synthesized by one-step heat treatment using phosphorous resin and CuCl₂ as raw materials,has a rich pore structure.The presence of Janus structure enables Cu₃P-Cu₂O/NPC to have both excellent HER catalytic activity of Cu₃P and excellent OER catalytic activity of Cu₂O,which can be used for both HER and OER catalytic reactions.In 1 M KOH,for its HER and OER,only need 138 mV and286 mV overpotential can reach 10 mA cm^-2 current density,respectively,and Tafel slope are respectively 62.64 and 79.02 mV dec^-1.When used in both HER and OER for total hydrolysis,only 1.57 and 1.81 V are required to achieve current densities of 10 and 50 mA cm^-2,respectively.At the same time,Cu₃P-Cu₂O/NPC also has excellent stability,can work for a long time in alkaline solution,after more than 168 h of total hydrolysis reaction,still can maintain the activity of more than 98%.