The Study Of Nonmetal-doped Electrocatalyst Synthesis And Their Performances In Catalyzing Water Electrolysis

Hydrogen is a kind of clean and renewable energy and well known as a desirable energy carrier for next generation power source.Water electrolysis is the most promising way to produce hydrogen on a large scale.At present,the bottleneck of hydrogen generation through water electrolysis technology is the lack of efficient,stable and cheap electrocatalyst.Many experimental results and theoretical calculations show that heteroatom doping can effectively improve the activity of electrocatalysts.Metallic cation doping has been widely studied,while nonmetal element doping has just emerged.Due to the much stronger electronegativity of nonmetal elements than metal elements,the electronic structure of materials can be readily engineered by nonmetal element doping.In this paper,we have systematically studied the synthesis of four kinds of nonmetal element doped electrocatalysts,including phosphorus doped molybdenum carbide phase MXenes?P-Mo₂CT_x?,phosphorus doped cobalt sulfide(P-Co_1-xS),sulfur doped nickel phosphide ultralong nanowires?S-Ni₂P NW?and sulfur doped iron phosphide?S-FeP@CFC?,and their application in catalyzing hydrogen evolution reaction?HER?.In the work of P-Mo₂CT_x,we incorporated phosphorus into Mo₂CT_x MXenes through a simple phosphorization course,which enlarge the d spacing of the?002?crystal planes of Mo₂CT_x MXenes.The phosphorized Mo₂CT_x MXenes exhibit significantly improved electrocatalytic performance toward HER compared with pristine Mo₂CT_x MXenes,with a dramatic decrease in overpotential(more than 100 mV at 10 mA cm^-2).Theoretical computation suggests that P doped Mo₂CT_x MXenes possess a metallic band structure and an optimal hydrogen adsorption,which lead to improved conductivity and electrocatalytic kinetics,respectively.This work not only advances the understanding of property-tunning of the latest two-dimensional materials MXenes,but also paves the way for the development of MXenes-based materials that can be applied in the field of energy conversion and storage.In the work of P-Co_1-xS,various cobalt sulfides(including CoS₂,Co_1-xS,and Co₉S₈)doped with P are anchored on carbon cloth through a facile hydrothermal method.Among tested electrocatalysts,P doped Co_1-xS exhibits excellent electrocatalytic performance with an overpotential of 110 and 165 mV for current densities of 10 and 100 mA cm^-2,respectively.Density functional theory calculations reveal that P doped Co_1-xS possesses a smaller bandgap and more optimal hydrogen adsorption sites than pristine Co_1-xS.This work initiates P doping into different cobalt sulfides and sheds light on HER activity improvement mechanism of P doping,which could guide the design of earth-abundant HER electrocatalysts for the‘hydrogen economy'.In the work of S-Ni₂P NW,a one-step synthesis of densely-packed ultralong S doped Ni₂P nanowire HER electrocatalysts is reported for the first time,which are obtained by direct phosphorization-sulfuration of commercially available nickel foam using phosphorus/sulphur mixed vapor.The nanowires prepared here have extremely high length to diameter ratio which ranges from 500 to 1000.The formation mechanism of such morphology is illustrated by a systematic study of the morphology,microstructure and elementary distribution of the nanowire array cathode.The ultralong nanowire morphology and novel‘1D@3D'structure clearly helps improve the HER performances,since the self-supported Ni₂P nanowire array cathode exhibits outstanding HER electrocatalytic activity and long-term durability in all of the acidic,alkaline,and neutral conditions.In the work of S-FeP@CFC,we originally develop a novel and inexpensive protocol to prepare S-incorporated FeP nanofilm electrocatalysts coating on commercial carbon fiber cloth?S-FeP@CFC?.Involving only atmospheric-pressure synthesis procedures makes such protocol both scalable and feasible.S-FeP@CFC has been optimized by slightly regulating the annealing temperature in its synthesis process.The optimized S-FeP@CFC exceed most of the previously reported nonmetal-incorporated/doped electrocatalysts in catalyzing HER.In acid electrolyte,it needs overpotential of only 83and 106 mV to achieve current densities of 10 and 20 mA cm^-2,respectively,with a 24-hour-long durability.Moreover,high activities superior and close to that of benchmark Pt are also observed for the optimized S-FeP@CFC in neutral and alkaline media,exhibiting excellent pH-universal catalytic HER performances.