Preparation Self-supporing Of Copper-based Nanomaterials And Study Of Electrocatalytic Water Splitting

Due to energy exhaustion and environmental pollution,renewable energy sources have received widespread attention.Hydrogen energy is an ideal renewable energy source with high energy density and pollution-free.Electrochemical water splitting is a simple and effective method for hydrogen production.Up to now,the frequently-used electrocatalytic hydrogen evolution（HER）and electrocatalytic hydrogen evolution（OER）electrocatalysts are Pt-based materials and the oxides of Ru or Ir,respectively;but the scarcity and high cost hinder their practical application.Based on the advantages of good electrical conductivity,low price and rich reserves,copper-based electrode materials are prepared and studied through elemental doping,carbon coating and structural changes.The main contents and conclusions are as follows:（1）Ultrathin carbon-coated Cu₂S-Cu₃P@C nanorod arrays are prepared through simple liquid-solid reaction,low temperature and heat treatment carbonization method.The optimum preparation process is determined by adjusting the carbon content of the precursor and the temperature of carbonization treatment.Physical and chemical characterization and electrochemical measurements are performed.Nanorod-like Cu₂S-Cu₃P@C with an average length of about 200 nm,average diameter of 76 nm grows vertically on copper foam.The self-support structure supported on copper foam can expose more active sites,which is beneficial to the rapid transport of electrons along the nanorods and facilitates the diffusion of reactive materials to active sites and the escape of gas.Electrochemical characterization shows that Cu₂S-Cu₃P@C exhibits excellent HER performance with a low onset potential of 48 m V,an overpotential of 85 m V at?10 m A cm^?2,a small Tafel slope of 34m V dec^?1 in 0.5 M H₂SO₄ solution and the accelerated test is carried out by cyclic voltammetry after 1,000 cycles,the HER performance is almost unchanged.Meanwhile,after 80 hours holding at?400 m A cm^–2,the decrease in activity is negligible,which indicates that the nanorod-like Cu₂S-Cu₃P@C with good stability.These results show that the carbon-coated nanowire structure provides an available way for preparing high performance electrocatalysts for the HER.（2）The Cu-Fe/CF nanowire that is uniform in size and interlaced into a mesh is grown on copper foam by hydrothermal method and it exhibits excellent electrocatalytic OER activity in 1.0 M KOH solution with an onset potential of259 m V,tafel slope of 79 m V dec^?1.Furthermore,the Cu_xFe_1-x/CF has small impedance as well as large surface area.Using selenium powder as selenium source,the surface morphology of the sample does not change after selenylation.The resulting Cu_0.41Fe_0.60Se_1.99/CF nanowire with diameter between 8～12 nm and the activity of OER is significantly increased.Compared to the pre-selenization sample,the onset potential of catalysts after selenization is about 200 m V,tafel slope is 46 m V dec^?1.The reasons are as follows:ⅰ)Cu_0.41Fe_0.60Se_1.99/CF nanowires with larger specific surface area can expose more active sites;ⅱ)the introduction of selenium is conducive to the adsorption of OH^?ions and promotes the catalytic reaction.In addition,the stability of Cu_0.41Fe_0.60Se_1.99/CF nanowires is estimated by chronopotentiometry method.After 70 h of continuous electrolysis,maintaining a current density of 100 m A cm^?2 and the slight change is observe,indicating that the catalyst has good stability.