Platinum Site Configuration And Activity Regulation In Hydrogen Evolution Reaction

With the increasingly serious problems of environmental pollution and energy shortage,it is urgent to find a renewable clean energy to replace fossil energy.Hydrogen is considered to be the most promising energy carrier in the future because of its high energy density,no pollution and reformability.Using wind/light and other renewable resources to generate electricity to drive electrolytic water to produce hydrogen is a green and sustainable energy path,which has attracted extensive attention from academia and industry.The development of anode and cathode catalysts in its system has become the core task of the development of electrolytic water to produce hydrogen.Noble metal Pt is the best catalyst for cathodic hydrogen evolution reaction（HER）,but its high price and resource scarcity limit its industrial application.Therefore,how to improve the activity of Pt sites and how to reduce the use of Pt metal,so as to develop Pt based catalysts with "cost reduction and efficiency enhancement"has become one of the hotspots of current research.To this end,researchers are trying some strategies,such as reducing the size of Pt and even reaching the monatomic level;Regulate the coordination environment and electronic structure of Pt sites to optimize site activity;The carrier lattice solidifies the Pt site to improve the catalytic stability of the site,and so on.Combined with the above objectives,this paper controls the binding Pt sites through two schemes:nano alloying and sulfide carrier solidification,and realizes the dual management of Pt component content and site environment.The two Pt based catalysts show excellent hydrogen evolution reaction activity,which is significantly higher than that of commercial Pt/C catalysts in terms of quality,activity and economic benefit.The details are as follows:1.By designing nano bimetallic eutectic alloys,we developed Pt co synergistic active units with charge polarization for acid-base universal hydrogen evolution reaction.Based on the adsorption reduction pyrolysis process control of ZnCo based metal organic framework（MOF）precursor,a hybrid catalyst of nitrogen rich doped porous carbon supported PtCo alloy nanoparticles was successfully prepared（PtCo@NC）,it can show excellent and stable HER activity in both acidic and alkaline electrolyte.Specifically,in acidic and alkaline electrolyte,the overpotential with current density of 10mA/cm2 is 34mv and 21 mV respectively.Since the Pt content in the catalyst is only 2.67 wt%,the activity per unit mass of Pt is significantly higher than that of commercial Pt/C catalyst,and better than most Pt based catalysts reported recently.Combined with experimental and theoretical analysis,the charge transfer between adjacent Pt and co atoms in the alloy forms an electropolarized atom pair unit,which optimizes the center position of the d-band of Pt and Co atoms and their absorption free energy to the reaction intermediates H*and OH*respectively,which not only promotes the dissociation of water molecules,but also accelerates the hydrogen evolution reaction,which not only optimizes the acidic HER activity of Pt sites,but also significantly enhances the alkaline HER activity through the synergistic effect of Pt-Co.This work provides a low Pt content HER catalyst and emphasizes the value of designing atomic level synergistic catalytic units.2.We designed and developed Ni3S2 nano sheet array dispersed anchored ultrafine Pt clusters（Pt-NiS）for alkaline hydrogen evolution reaction by photo-controlled deposition.The hydrothermal Ni3S2 nanosheet arrays on the three-dimensional porous conductive nickel foam（NF）substrate have a certain photoelectric effect,which controls the photoreduction deposition of Pt clusters and realizes the dispersion anchoring of ultrafine Pt sites.Compared with the commercial Pt/C catalyst and its coated electrode,the developed Pt-NiS-NF catalytic electrode has the following advantages:（1）the three-dimensional multistage support structure has a larger specific surface area,which is conducive to the loading and exposure of Pt sites;（2）The size of Pt clusters anchored by photo controlled deposition is less than 4nm,with good monodispersity,interface crystallization and solidification,stable and non agglomeration;（3）The interface Ni-S-Pt chemical coordination and electron transfer modulate the electronic structure of Pt and Ni sites,and optimize their adsorption free energy for H*and OH*respectively,which is conducive to give play to the synergistic effect of bimetallic sites and promote the dissociation and activation of water molecules;（4）The self-supporting structure does not need the intervention of adhesive（such as Nafion）bonding and coating process,which not only avoids the problems of high contact resistance and unstable falling off caused by adhesive,but also simplifies the electrode manufacturing process and reduces the process cost.The performance test results show that Pt-NiS-NF The overpotential of the electrode to reach 10mA/cm2 current density in alkaline water electrolyte only needs 53mV,and the content of Pt is only 1.2 μg/cm2,which is significantly superior to the commercial Pt/C catalyst in terms of Pt mass activity and operation stability.In this work,a self-supporting electrode for in-situ anchoring ultra-fine Pt sites was developed,which provides an idea for the design of Pt based catalyst carrier integrated electrode.