Electro-and Photoelectrocatalytic Water Splitting Based On MXene And Transition Metal Hydroxide Composite Catalysts

Hydrogen is the most abundant resource in the entire universe,which constitutes75%of the mass of the entire universe.Under the current situation of increasingly exhausted fossil energy,hydrogen is called the ultimate energy source of mankind.Hydrogen is secondary energy and needs to be produced from hydrogen-containing substances such as water and fossil fuels.Water is a large"storage"of hydrogen.The efficient production of hydrogen energy from water can greatly reduce the use of non-renewable energy sources such as petroleum and coal mines in the future.During Water splitting,hydrogen and oxygen are both produced,in which the process of generating hydrogen from water is a two-electron transfer reaction,and the generation of oxygen is a four-electron process.Therefore,higher energy is required to overcome the kinetic obstacles that occur in the process of generating oxygen.In exploring the technology of water splitting to produce hydrogen,in-depth research through electrochemical and photoelectrochemical methods has great potential,in which developing efficient anode and photoanode catalysts are the key to overcome the slow water oxidation kinetics.In this work,the water oxidation Fe and Co layered double hydroxides?FeCo-LDH?is combined with the two-dimensional material MXene?Ti₃C₂T_x?to obtain a new composite water oxidation anode catalyst FeCo-LDH/MXene.The addition of MXene nanosheets can effectively prevent the aggregation of FeCo-LDH and increase the active sites.FeCo-LDH/MXene exhibits a higher electron transfer capability and a larger electrochemically active surface area.Due to the efficient synergy between the atoms in FeCo-LDH/MXene,the electrocatalytic water oxidation activity has been significantly improved.At a current density of 10 mA cm^-2,the overpotential is only268 mV and the performance is significantly better than that of graphene or multi-wall carbon nanotube modified by FeCo-LDH.Due to the appropriate band gap?2.4 eV?,the n-type semiconductor BiVO₄ material can absorb visible light and is widely used in the research of photoelectric catalytic water splitting,but its slow kinetics limits extensive development.In this paper,MXene?Ti₃C₂T_x?is modified on the surface of BiVO₄,the good structure and charge transport characteristics of MXene are used to enhance the surface hole transport efficiency of BiVO₄.The NiOOH transition metal nanomaterials are modified on the surface of MXene/BiVO₄ as a cocatalyst by electrodeposition.The results show that the synergistic effect of MXene and NiOOH significantly improves the photoelectric catalytic water oxidation performance.When the applied voltage is 1.23 V vs.RHE,the photocurrent density of NiOOH/MXene/BiVO₄ can reach 4.47 mA cm^-2?...