Study On Anion Regulation Of Iron-based Catalysts And Their Performance For Water Splitting

The pollution problems caused by the excessive consumption of traditional energy have force us to seek a clean,efficient and sustainable alternative energy source.As a green,clean energy source,hydrogen energy is considered to be an ideal carrier for energy storage and supply in the future.Hydrogen production by electrolysis of water splitting can make full use of non-grid-connected green energy sources,and has received widespread attention.However,its bottleneck is mainly the anodic oxygen evolution reaction?OER?.Therefore,it is the key to produce a highly efficient and inexpensive anode oxygen evolution catalysts to produce hydrogen from electrolyzed water.Transition metal-based catalysts such as Co,Ni,Fe,etc.have a wide range of sources,low cost and good OER performance,thus can be used as an excellent basic catalyst for electrolyzed water.The modification of the transition metal-based catalyst,such as doping non-metal elements,is expected to obtain a highly efficient electrolyzed water catalysts.In this paper,we use a variety of methods for element doping of iron-based transition metal catalysts to achieve a good effect of surface modification.The main content is mainly divided into four aspects as follows:?1?A series of CoFeP/NC catalysts were synthesized by a simple gas-solid phase reaction,which exhibited excellent OER performance.The results show that the Co_0.35Fe_0.17P_0.48/NC amorphous nanorod catalyst has the best OER performance.Through a series of physical characterizations,we attribute its excellent properties to its amorphous structure,Fe-doped and carbon-nitrogen coated structure.Besides,under the alkaline conditions,the overpotential of the catalyst on the glassy carbon electrode was only 257 mV and the Tafel slope was 31 mV/dec.?2?The NiFe₂O₄-12Pi catalyst was synthesized by the method of equal volume impregnation to dope the element P for NiFe₂O₄ catalyst and obtained NiFe₂O₄-12Pi catalyst ultimately,which modificate the surface of the catalyst.The result of element doping is to achieve a uniform distribution of P elements,and the oxygen evolution activity is greatly improved:comparing with the original catalyst,the overpotential of NiFe₂O₄-12Pi nanoparticles is reduced from 440 mV vs.RHE to 330 mV vs.RHE,and the tafel slope is reduced from87 mV/dec to 57 mV/dec.In addition,the morphology and structure of the NiFe₂O₄-12Pi catalyst remained unchanged before and after the OER tests compared with the NiFe₂O₄ catalyst,showing excellent stability.?3?A simple and rapid electroless plating method was designed to grow FeB-Ni nanoflower catalyst in situ on nickel foam at room temperature.In 1 M KOH solution,the catalyst can be used as an excellent bifunctional electrocatalyst.Its oxygen evolution overpotential and hydrogen evolution overpotential at 10 mA/cm² are 250 mV and 58 mV,respectively.Under the same conditions,the FeB-Ni catalyst exhibits a fairly good performance for overall water splitting,requiring a cell voltage of 1.63 V to afford 10 mA/cm².Combined with a series of physical characterizations,it is proved that the excellent dual-functionality of the catalyst depends not only on the larger active area,but also on its internal fast electron transfer rate.?4?An amorphous tapered array catalyst FeP-Ni was synthesized by the method of electroless plating method.In 1 M KOH solution,the catalyst also exhibits excellent dual function of electrolyzed water.At the current density of10 mA/cm²,its oxygen evolution overpotential and hydrogen evolution overpotential are 218 mV and 120 mV,respectively.Under the same electrolyte conditions,the electrolysis cell using the FeP-Ni catalyst couple requires a cell voltage of 1.65 V to afford a current density of 10 mA/cm².It is proved combined with physical characterization that the in-situ grown phosphide effectively promotes the electrolyzed water performance of the catalyst,and the advance of electroless plating method was verified simultaneously.