Study On Preparation And Performance Of Cobalt-based Electrocatalysts Doped With B And P For Water Splitting

The exhaustion of global fossil fuels and the aggravation of environmental pollution have made human beings more urgent for new energy.Hydrogen energy is considered as the most promising alternative to fossil energy as the main energy in the future.There are limitations in the use of low-quality energy such as solar energy.The combination of solar power generation and water electrolysis technology enables the conversion of low-quality energy into hydrogen energy with high energy density for storage and use.The key of electrochemical water-splitting technology lies in the economy and efficiency of the electrodes,the noble-metal catalysts has excellent performance,but it's"high price and less quantity",therefore,the purpose of this study is to prepare cost-effective non-noble metal catalysts,in order to solve low-cost and high efficiency of the electrodes of electrocatalytic water-splitting.Noble metal catalysts have excellent performance,but"high price and less quantity",so the development of non-noble metal catalysts is an important step in large-scale hydrogen production.In this paper,the influence of the doping of nonmetal boron and phosphorus and the introduction of Mo and W on the electrolytic water catalyst of Co-based binary metal is studied.The catalytic performance and stability of catalyst samples were evaluated by cyclic voltammetry/linear sweep voltammetry,electrochemical impedance spectroscopy,turnover frequency,Faraday efficiency and chronopotential method.The results are as follows:(1)The composition of electrolyte,the current density,pH,the process conditions and the deposition time have a great direct influence on the catalytic performance in double-pulse electrodeposition.Optimal ratio of CoMo system:CoCl2·6H2O 0.12mol/L,NaH2PO2·H2O 0.2 mol/L,H3BO3 0.3 mol/L,Na2MoO4·2H2O 0.15 mol/L,pH=5,positive/negative pulse average current density 0.55/0.175 A/cm~2,deposition time 15min;Optimal ratio of CoW system:CoCl2·6H2O 0.10 mol/L,NaH2PO2·H2O 0.3 mol/L,H3BO3 0.3 mol/L,Na2WO4·2H2O 0.06mol/L,pH=6,positive/negative pulse average current density 0.35/0.135 A/cm~2,deposition time 12 min.(2)In 1 mol/L KOH alkaline solution,overpotential of HER and OER for Co-Mo-B-P/CF catalyst were 48 mV and 275 mV at 10 mA/cm~2,respectively,and Tafel slope of HER is 40 mV/dec.The reaction followed the volmer-heyrovsky path,indicating that H degradation is a rate control step.The metal active sites are mainly Co~?/Co~? and Mo~?.The enhancement of B/P doping CoMo catalyst activity is due to increase of specific surface area from the micrball and nanosheet composite structure,the electron contribution of B/P to the Co/Mo active site,the reduction of the charge transfer impedance,and the direct deposition of the catalyst on the surface of the carrier with high conductivity.(2)Overpotential of the Co-W-B-P/CF catalyst for HER and OER is 65 mV and280 mV at 10 mA/cm~2,respectively,and corresponding Tafel slope is 43 and 103mV/dec,indicating that the majority of H2 were generated through the volmer-heyrovsky step.The metal active sites are mainly Co~?/Co~? and W~?/W~0.The co-existence of amorphous and crystals in the Co-W-B-P/CF catalyst is conducive to adsorption of reactants.The poor conductivity of amorphous catalysts is partly overcome due to catalysts were directly electrodeposited on the copper foam.