Construction And Water Electrolysis Properties Of Nickel-doped Cobalt-based Transition Metal Phosphides

With the development of society,human society will face increasingly serious energy and environmental problems.Thus,the development of new energy has become an urgent need of mankind.As a new energy source with high energy density,large storage capacity,clean properties,hydrogen energy is highly expected by human beings.Currently,electrolytic water hydrogen production technology is the most effective method to obtain green hydrogen,but noble metals as catalysts have to be used in the water decomposition process.Therefore,non-noble metal electrolytic water catalysts have become a hot spot for current research.Compared with other transition metal phosphides,Co-based transition metal phosphides（Co-TMPs）are a promising catalyst with quite suitable Fermi energy level and d-band center,and the exchange current density（j0）is at its peak location.However,for the electrocatalytic performance of Co-TMPs,there is still some distance away from that of noble metal catalysts.For this reason,in this thesis,Ni is doped into Co P by doping engineering to obtain hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）bifunctional catalysts with lower overpotentials.The experimental results are obtained as follows:1.NiCoP/NF catalysts with hexagonal inclusion and nanocapsules doped with Ni are prepared by a combination of hydrothermal method and transition metal doping followed by phosphorization of Ni-Co bimetallic hydroxide（Ni Co-DH）grown on nickel foam（NF）substrate.Ni Co P/NF possesses a suitable electronic structure and its unique morphological structure ensures that Ni Co P/NF has more active sites and larger specific surface area,beneficial for the improvement of the catalyst.2.Electrochemical tests in 1.0 M KOH show that the overpotentials of Ni Co P/NF at 10 m A/cm² are 42 m V and 237 m V,respectively,for HER and OER.In addition,the voltage of overall water splitting is only 1.505 V at a current density of 10 m A/cm²when used as both cathode and anode.Moreover,the stability can be maintained for more than 100 h at a current density of 1000 m A/cm².In seawater,the voltage of overall water splitting of Ni Co P/NF is only 1.567 V at 10 m A/cm² and maintained stability for more than 100 h at a current density of 1000 m A/cm²,which are more than most reported bimetallic phosphides.3.Through density functional theory（DFT）calculations,it is demonstrated that the doping of Ni can effectively adjust the electronic structure of Co P and reduce the Gibbs free energy(ΔG_H*),thus enhancing its HER properties.