Construction Of Hollow Mesoporous Carbon-confined Ruthenium Nanocatalyst And Study On The Performance Of PH-universal Hydrogen Evolution Reaction

With the depletion of fossil fuels and increasingly serious environmental pollution,the development of sustainable,renewable and green energy has become the key to future economic development.Hydrogen energy,as a clean and high-quality energy source,has been widely concerned by researchers.Hydrogen production by electrolysis of water is an efficient and convenient way to produce hydrogen.Design of efficient and stable hydrogen evolution reaction（HER）electrocatalysts for mass production of hydrogen via electrochemical water splitting is a challenging but urgent task.Although platinum（Pt）based material is the best HER catalyst at present,its large-scale application is restricted because of its high price and scarce earth reserves.Ruthenium（Ru）has similar hydrogen bonding strength to Pt,superior hydrolytic dissociation ability and wide p H range stability,and has become a hot spot in the field of catalytic HER.However,the high surface energy of Ru nanoparticles/nanoclusters（Ru NPs/NCs）leads to easy aggregation and migration during preparation and reaction,which seriously affects the utilization rate and activity of the catalyst.Therefore,it is essential to explore a stable and efficient HER catalyst with high Ru atom utilization rate in the whole p H range.It is one of the best ways to improve the accessibility and stability of Ru active sites by anchoring Ru NPs on a carbon substrate with good conductivity and acid and alkali corrosion resistance.Hollow mesoporous carbon,with high specific surface area,rich porosity,through-hole inside and outside,large cavity and good conductivity,accelerate the diffusion and electron transfer rate of reactants and products,and become an excellent carbon carrier material.If Ru is directly loaded on mesoporous carbon,the stability of Ru in the reaction process cannot be guaranteed because of the weak interaction between Ru and mesoporous carbon surfaces.Therefore,it is the key to determine the activity and stability of the catalyst to explore a way to stabilize Ru on mesoporous carbon.In this paper,Ru/HMCs-x,HMCs@Ru,Ru@HMCs,Ru/S-HMCs and Ru NCs/Sx-HMCs were prepared by confining Ru in the pores rich in mesoporous carbon（HMCs）,which were used to study the performance of HER at p H-universal,the specific research contents and work are as follows:1.The hollow mesoporous carbon embedded Ru NPs catalyst（Ru/HMCs-500）was prepared by modified St?ber method and sodium borohydride reduction method,and its HER catalytic activity and stability in the whole p H range were studied.Hollow mesoporous carbon（HMCs-x）with controllable pore size were prepared by adjusting the concentration of ammonia water.Accurate design of pore and Ru NPs size successfully prepared Ru/HMCs-500 catalyst.The experimental results show that the mass activity of Ru/HMCs-500 in 0.5 M H₂SO₄,1 M KOH and 0.5 M PBS solutions is 1.3,7.0,and 3.8 times higher than that of Pt/C at an overpotential of-50 m V（vs.RHE）,respectively.The characterization results reveal that Ru NPs with embedded structure confined by pores has high dispersibility and is not easy to lose or agglomerate,which ensures the long-term catalytic stability and activity,which greatly improves their intrinsic activity and reduces the activation energy of HER.This work provides an idea for designing HER catalyst with high activity in full p H medium.2.A simple hydrothermal selective in-situ polymerization strategy was designed to accurately control the anchoring point of Ru in hollow mesoporous carbon spheres（HMCs）（outer surface,HMCs@Ru;cavity,Ru@HMCs;and pore channels,Ru/S-HMCs）.The HER mechanisms of the three catalysts over a wide p H range were revealed by analyzing the loading position,content,dispersion,particle size,and valence state of Ru.HMCs@Ru showed excellent area activity,with overpotentials of 64.3,2.8,and 78.1 m V at 10 m A?cm^-2 in 0.5 M H₂SO₄,1 M KOH and 0.5 M PBS solutions,respectively.Ru/S-HMCs exhibit high mass activity,with values 43.3,2.9,and 12.7 times those of Pt/C in 0.5 M H₂SO₄,1 M KOH and 0.5M PBS media,respectively,at-50 m V.After 2000 cyclic voltammetry cycles,the performances of HMCs@Ru and Ru/S-HMCs hardly decreased,indicating good stability.The excellent electrocatalytic activity can be attributed to two main factors:（1）the confinement effect,which not only promotes high Ru dispersion but also prevents the leaching of active metal under harsh conditions,and（2）their excellent structural characteristics,the catalyst structure features a large cavity located in the center（～160 nm in diameter）and an ultrathin monolayer of mesopores（～6 nm）uniformly distributed on the hollow shells,ensuring fast mass diffusion and electron transfer kinetics,as well as complete accessibility of catalytic sites.3.S-doped graded mesoporous carbon pore confined Ru nanocluster（Ru NCs）catalysts（Ru NCs/S-HMCs）were prepared by combining modified St?ber method with hydrothermal method.H₂S produced by thiourea decomposition under high temperature hydrothermal conditions tends to enter rough mesoporous carbon channels,and Ru³⁺introduced into mesoporous carbon channels under electrostatic action was reduced to Ru NCs by high-temperature hydrothermal treatment.High temperature annealing S was successfully doped into the mesoporous carbon shell around Ru NCs.The effects of different Ru/S feed ratios and S precursor addition sequence on the materials were explored.It is worth noting that halving or doubling the doping amount of S will lead to the formation of Ru O₂,with insufficient S exposing the Ru O₂（110）crystal plane,while excessive S mainly exposes the（101）crystal plane.The experimental results show that the incorporation of S improves the kinetics of Volmer process and reduces the hydrogen adsorption energy barrier.Ru NCs/S-HMCs showed excellent HER activity at all p H conditions.At the current density of 10 m A?cm^-2,the low overpotential of 63.5 m V,3.5 m V and 61.0 m V were shown in 0.5 M H₂SO₄,1 M KOH and 0.5 PBS solutions,respectively.The mass activity of Ru NCs/S_0.5-HMCs in acidic,alkaline and neutral media is2997.6,21542.2,and 7088.1 m A?mg^-1,which is 4.8,77.2,and 59.5 times that of Pt/C,respectively,and it has obvious practical value.This work provides a reference for the preparation of small molecule-assisted anchored metal particle catalysts.