Structure Regulation And Performance Of Carbon-nitrogen Supported Ruthenium-based Hydrogen Evolution Electrocatalysts

Since the implementation of the "double carbon" strategy,promoting the transformation of traditional energy to green and low-carbon has become the top priority for socio-economic development.Hydrogen energy as a high energy density,zero emission of sustainable clean energy has been widely concerned.Among the existing hydrogen production technologies,electrolytic water for hydrogen production is high efficiency,mild conditions and environmentally friendly.Water splitting consists of hydrogen evolution reactions(HER)and oxygen evolution reactions(OER),where the high overpotential during the reaction greatly limits the efficiency of hydrogen production.At present,platinum(Pt)based catalytic materials,which have been widely recognized internationally,show excellent catalytic activity in electrocatalytic water splitting,but their largescale application is restricted by the problems of high cost and lack of resources.Therefore,the development of a low-cost and efficient hydrogen evolution catalyst has become the focus of research.Ruthenium(Ru),one of the cheap Pt group metals,has become the most promising Pt-based catalyst alternative.Due to the fact that Ru-H has a similar strength to Pt-H,it facilitates the hydrogen desorption process and exhibits Pt-like HER activity.Nevertheless,Ru-based nanocatalysts still have great room for improvement,and there is a lack of systematic research on their reaction mechanism and active center.In this thesis,guided by the performance regulation of carbon and nitrogen supported ruthenium-based hydrogen evolution electrocatalysts,the morphological structure,crystal structure and electronic structure of rutheniumbased catalysts were regulated by lattice confinement strategy,heterogeneous metal interface regulation strategy and crystal phase engineering strategy,respectively,to explore their HER performance in different pH environments.The main research contents are as follows:(1)The RuNP-RuSA@CFN-800 by three-dimensional fullerene network lattice(CFN)lattice-confined Ru nanoparticles(RuNP)and single atoms(RuSA)was successfully obtained by solvothermal-thermal sintering method.RuNPRuSA@CFN-800 revealed significantly superb alkaline HER activity,with a current density of 10 mA cm-2 only requiring an overpotential of 33 mV,and the ultra-stable CFN substrate enables stable hydrogen production for over 1400 h.At the industrial level,an overpotential of 251 mV can provide a large current output of 1000 mA cm-2.The experimental and density functional theory(DFT)results showed that the electronic synergistic effect between RuNP and RuSA can effectively adjust the charge distribution of RuNP-RuSA@CFN-800,reduce the Gibbs free energy of the intermediate product in the hydrolysis process,and accelerate the electrocatalytic kinetics of HER.This work provides a general route for the construction of ultra-stable alkaline hydrogen evolution electrocatalysts.(2)The Pt/Ru@CFN bimetallic hydrogen evolution catalyst with heterogeneous metal interface was successfully prepared by two-step solvothermal-thermal sintering method.Pt/Ru＠CFN showed excellent acidic and alkaline HER activity.At a current density of 10 mA cm-2,the hydrogen evolution overpotentials of Pt/Ru@CFN in 0.5 M H2SO4 and 1 M KOH solutions were 36.2 and 63.1 mV,respectively.The heterogeneous interface formed between Pt and Ru can not only increase the number of active sites in the system,but also optimize the electron configuration of Ru and Pt,providing a new path for charge transfer in the material and ultimately improving the electrocatalytic HER performance.This work provides a novel idea for the design of efficient metal-based acidic and alkaline hydrogen evolution catalysts.(3)The fcc/hcp-RuNP/CN polycrystalline ruthenium-based catalyst with the coexistence of face-centered cubic(fcc)Ru and hexagonal(hcp)Ru for all-pH was successfully synthesized by one-step solid-phase sintering method.The newly synthesized fcc/hcp-RuNP/CN exhibited excellent HER catalytic activity at pHuniversal conditions,required overpotentials of only 16.8,23.8 and 22.3 mV in 1 M KOH,0.5 M H2SO4 and 1 M PBS to reach 10 mA cm-2,respectively.At the same time,fcc/hcp-RuNp/CN can achieve industrial applications in both alkaline and acidic environments,and the overpotentials are only 275.9 and 285.8 mV at 1000 mA cm-2,respectively.The stacking fault formed between metastable fcc-Ru and stable hcp-Ru phase interface can effectively adjust the electronic structure of the catalyst,promote the electron transfer during the reaction process,optimize its adsorption capacity for hydrogen,and lead to the improvement of HER activity of the catalyst.This work provides a fresh method for the construction of the universal pH-stable metal-based hydrogen evolution electrocatalysts.