Preparation Of Nickel Phosphide Micro-nano Structure And Study On Its Electrocatalytic Hydrogen Evolution Performance

With the increasingly problems of energy crisis,environmental pollution and greenhouse effect,the development of renewable and clean energy has been extremely urgent.Hydrogen is a non-pollution and renewable energy source,with its high energy density(between 120 and 140 MJ kg-1),environment-friendly nature,abundant reserves,convenient storage.Therefore,hydrogen is regarded as an ideal efficient energy carrier in the future.Among the many hydrogen production technologies,the production of hydrogen through Water splitting is potentially of great importance in solving the energy crisis and environmental problems.Efficient and stable catalyst are essential in the production of hydrogen by water splitting.It is well known that the platinum-based catalysts exhibit unparalleled catalytic performance for the hydrogen evolution reactions(HER)of electrochemical water splitting,such as low overpotentials,low starting potentials and low Tafel slopes.But the high cost and scarcity of platinum-based catalysts,large-scale hydrogen production was limited.The development of low cost-effective and earth-abundant alternatives with high HER activity and stability has attracted much research attention.Nickel phosphides have been widely attention and research for HER catalysis due to their high activity and durability.In this paper,two novel nickel phosphide HER catalysts were prepared and hydrogen evolution performance have been studied.The research achievements are listed as follows:(1)A facile,effective,and practical phosphidation strategy was developed to prepare novel self-supported porous nickel phosphide nanosheets.As-prepared self-supported Ni5P4/NiP2 porous nanosheets exhibits excellent HER performance in acidic solution,and a relatively low overpotential of 92 mV at the current densities of 10 mA·cm-2,with the small Tafel slope of 52.8 mV·dec-1.The outstanding HER activity of the porous NisP4/NiP2 nanosheets can be attributed to the high electrochemically active surface area provided by the complete phosphidation reaction and the synergistic effect between NisP4 and NiP2 phases.The porous NisP4/NiP2 nanosheets exhibited excellent stability under both accelerated degradation test and long-term durability test.This method can be employed to prepare large-area self-supported porous NisP4/NiP2 nanosheets with nearly same HER activities and long-term stability,indicates that it has potential for practical application.This work paved a new avenue for the preparation of transition-metal phosphides HER catalysts in a facile,stable,and practical manner to promote their commercial applications.(2)Development a very convenient and scalable method,combined with electroless nickel planting technology and high-efficiency phosphating method to realize the preparation of novel porous nickel phosphide nanosheet arrays on different substrate.The as-prepared porous Ni5P4/NiP2/Ni2P nanosheet arrays on carbon cloth exhibits excellent HER performance in acidic solution,and a relatively low overpotential of 63 mV at the current densities of 10 mA·cm-2,with the small Tafel slope of 47.3 mV dec'1.The HER performance is superior to recently published non-noble metal catalysts for HER in acidic media.The outstanding HER activity can be attributed to the high electrochemically active surface area and the synergistic effect between Ni5P4,NiP2 and Ni2P phases.The porous Ni5P4/NiP2/Ni2P nanosheet arrays exhibited excellent stability under both accelerated degradation test and long-term durability test.Ni-P/CC-60-450 shown good tenacity and this method can be employed to prepare large-area porous Ni5P4/NiP2/Ni2P nanosheet arrays with nearly same HER activities,suggesting a high potential for practical application.Besides,this method was used to prepare porous self-supported nickel phosphide nanosheet arrays by leaf vein(LV)and silkworm cocoon(SC)as substrates,both shows highly active electrocatalysts for hydrogen evolution reaction,which indicates that the method can overcome the problem of whether the substrate is conductive.It can be expected that this work provide approach is a universal method to produce transition-metal phosphides on different substrates for HER catalysis.