Construction Of Carbon-encapsulated W2C/WP Heterostructure And The Study On Electrocatalytic Performance For Her

Due to the massive depletion of traditional fossil fuels and the urgent need to achieve carbon neutrality,the development of sustainable and feasible energy storage and conversion technologies is particularly important.Hydrogen,with its high mass energy density and non-polluting combustion products,is currently considered as the most promising alternative to fossil fuels.Water electrolysis powered by renewable energy is the most promising way to produce high-purity green hydrogen on a large scale.Therefore,there is an urgent need to develop non-precious metal catalysts with high performance and low cost to effectively improve the water splitting performance.Tungsten-based compounds with low cost,abundant earth content and excellent catalytic performance are expected to replace Pt-based catalysts as the preferred electrocatalyst materials for promoting HER.However,due to poor electrical conductivity and stability,the practical application of tungsten-based electrocatalysts in large-scale sustainable hydrogen production is still greatly hindered.In this paper,the heterogeneous structure of carbon-coated W₂C and WP was constructed.The carbon composite can improve the conductivity and stability of the material.The synergistic effect between different phases can improve the charge transfer of the composite catalyst and expose more active sites.The specific research contents and results are listed as follows:（1）In the first section,W₂C nanospheres were prepared as a hydrogen evolution catalyst by a two-step method,followed by optimization of synthesis conditions,detailed morphological and structural characterization,and electrochemical performance tests.First,the morphology,crystal phase and structure of the precursor were changed by adjusting the synthesis temperature.W₂C/C synthesized at 25 ^oC had the best morphology and electrochemical performance.It required 145 m V overpotential to obtain the current density of10 m A cm^-2,which is significantly lower than the overpotential required by W₂C/C synthesized at 0 ^oC and 75 ^oC.Secondly,the effects of carbonization temperature on W₂C/C crystal phase,crystallinity and graphitization degree of carbon materials were studied.The W₂C/C-800 product obtained by carbonization at 800 ^oC had stronger electrical conductivity and higher electrochemical surface area,and showed superior HER activity.It required an overpotential of 145 m V to obtain a current density of 10 m A cm^-2 and the Tafel slope was 85m V dec^-1.It had good cyclic stability,the current density only had a slight loss at 145 m V overpotential after 2000 CV cycles.（2）In the second section,the W-PDA precursor was phosphated at high temperature,constructed a novel heterostructure（W₂C/WP@C）composed of W₂C and WP as an efficient HER electrocatalyst.Then the morphology,composition,valence state and electrochemical properties were characterized in detail.The contents of W₂C and WP in the catalyst were regulated by adjusting the ratio of W source and P source,so as to explore their influence on the degree of graphitization and charge transfer rate of the material.W₂C/WP@C-1 had higher conductivity,better charge transfer rate and larger electrochemical surface area,thus showing excellent activity and stability.It only needed an overpotential of 120 m V to obtain a current density of 10 m A cm^-2,and the corresponding Tafel slope was as low as 70 m V dec^-1.The W₂C/WP@C-1electrode was electrolyzed in water for 12 h in acidic medium,and the current density loss was only about 24%.