The Investigation Of Ni-based Non-precious Metal Multi Composites Bifunctional Electrocatalysts For Overall Water Splitting

The rapid economic and social development has led to increasing energy demand and irreparable environmental damage.The continuous consumption of fossil fuels has aroused people's high attention to the energy crisis.People are eager to find alternatives to sustainable non-renewable resources.Hydrogen is widely concerned for its advantages of clean,safe,and non-polluting and renewable characteristics.There are many methods to product hydrogen,hydrogen produced by electrolyzed water can use other renewable energy sources to generate electricity,and use the inexhaustible water resources on the earth to prepare high-purity hydrogen.The bottleneck of hydrogen production during overall water splitting is the large overpotential in the oxygen evolution reaction of anode.Therefore,developing bifunctional catalysts for overall water splitting with high electrocatalytic activity have far-reaching research significance.Ni-based binary and ternary non-precious metal composites bifunctional electrocatalysts are prepared through experimental optimization.The catalysts were characterized by SEM,XRD and XPS etc.,and electrochemical performance was investigated in 1.0 M KOH during the hydrogen evolution reaction,oxygen evolution reaction and overall water splitting.The catalytic mechanism was discussed and the main results achieved are as follows:(1)A 3D flowered-like spherical Ni3S2/MoS-2 nano-heterojunction bifunctional catalyst was prepared by a simple one-step hydrothermal method.We use Ni3S2/MOS2 as both anode and cathode in overall water splitting system,it shows excellent catalytic performance in both hydrogen evolution reaction and oxygen evolution reaction.The current density reaches 10 mA·cm-2 only need 184 mV and 116mV overpotential for HER and OER,respectively.And when the current density reaches 10 mA·cm-2,only 1.522 V applied voltage is required.This original bifunctional catalysis electrode with specific morphology offering large active sites and high catalytic activity using a simple hydrothermal method preparation shows great potential for overall water splitting.(2)The urchin-like ternary composite nano-bifunctional electrocatalyst Mn02/NiMoS was prepared by two steps of hydrothcrmal.Experiments show that the catalyst only needs 1.514 V applied voltage to reach 10 nA·cm-2,and it has highly catalytic activity and stable morphology for 20 hours.The main reasons are as follows:First,the catalyst is a macroscopically 3D structure,it is consisted of 2D nanosheets and 1D nanorods.The mesoporous structure provides a large number of catalytically active sites.And it is a reliable substitute for precious metal catalysts.The crystal of MnO2 is ?-MnO2.The ?-MnO2,rich of high concentration of potassium ions is full of defects,while the oxygen concentration active interrmediates such as OH*and OOH*provide a large number of active sites.Thereby it can accelerate the catalytic of oxygen evolution and overall water splitting of the catalysts.