Design Of Dual-site Hybrid Electrocatalysts For Hydrogen Evolution Reaction

As an economical and efficient secondary energy carrier,hydrogen can be used as the main reducing agent and energy source in hydrogen metallurgy,which is the important basis of green development of metallurgy and the"hydrogen economy".Electrolysis of water-splitting reaction,which can utilize the stable electricity driven from renewable energy?solar,wind,etc.?,is one of the most promising technology as a sustainable source of hydrogen.However,because the expensive price and scarce resources of Pt,which is the benchmark electrocatalyst toward hydrogen evolution reaction?HER?,the development of traditional electrolysis is greatly restricted.Meanwhile,the abundant transition metal catalyst,such as Ni and Fe,normally require high overpotential to boost HER,resulting in low efficiency and high power loss,which severely limits the large-scale application.Moreover,since the different reaction pathway,it has been reported that the state-of-the-art electrocatalyst?Pt?for hydrogen evolution reaction?HER?in acidic media,exhibits relatively sluggish kinetics in alkaline media,being at least two orders of magnitude slower than those in acidic media.In this context,this thesis demonstrates three hybrid electrocatalysts to boost HER.The design of various catalysts based on the different reaction steps in acidic or alkaline media and all these three catalyst have dual active site for HER.All as-resulted dual-site catalysts are better than the single-site catalysts towards HER,confirming the hybrid is more effective and these works will provide an experimental and theoretical basis for the rational design and application of industrial catalysts.The design and preparation of hybrid materials will also be beneficial to the investigation of electrode materials in electrocatalysis,supercapacitors and metal-air batteries.The main contents are as follows:?1?A functionalized Ni Ru-hydroxide?NiRu-OH?catalyst that acts as a capable candidate to immobilize highly dispersed single Pt atoms is described.We synthesize this catalyst by means of Ru leaching from a NiRu-layer double hydroxide?NiRu-LDH?under oxygen evolution reaction?OER?conditions.The hybrid catalyst shows extremely high HER activity,with an overpotential of 38 mV to drive a typical current density of 10 m A cm^-22 in alkaline media.We ascribe the excellent catalytic activity to the synergistic effect of the highly dispersed single Pt atoms and NiRu-OH in a dual-site alkaline HER mechanism.?2?A hybrid electrocatalyst consisting of Ru clusters trapped in NiCo-layered double hydroxide?NiCo-LDH?as the basis for an efficient hydrogen evolution reaction?HER?in alkaline media.Benefiting from the fast water dissociation kinetics on NiCo-LDH and favorable H recombination on Ru,the resultant Ru-Ni Co-LDH shows an extremely low HER overpotential of 28 mV at a current density of 10 mA cm^-22 with a small Tafel slope of 42 mV dec^-1.This superior catalytic activity can be ascribed to its high charge transfer ability and to the synergistic effect of the highly dispersed Ru and the Ni Co-LDH.Moreover,we also found that the oxidized Ru incorporated in NiCo-LDH was entirely reduced to Ru⁰ under hydrogen-evolution conditions,which suggests that Ru⁰ is the true catalytically active phase responsible for the outstanding HER performance.?3?In order to increase the active sites on the basal plane of Mo S2,a cyclic voltammetry?CV?cycling method was used to synthesize a catalyst comprising deposited Pt nanoparticles on MoS2 nanoflake stack structures on stainless steel mesh?SSM?.Compared with single materials?Mo S₂ or Pt particles?,the hybrid structure exhibits significantly enhanced hydrogen evolution reaction?HER?catalytic activity with an overpotentials of 87 mV at 10 mA cm^-2.The excellent HER performance should be attributed to the increase of active sites and improvement of intrinsic activity of MoS₂.