Controllable Synthesis Of Metal Ruthenium Cobalt Atomic-Scale Electrocatalysts Toward Organics Oxidation

Electrocatalytic water splitting has been regarded as the most promising technology for hydrogen production,which plays a vital role in resolving environmental problems caused by traditional fossil.Two half-reactions of hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）are often involved in electrocatalytic water splitting,and their theoretical overpotentials are 0 V and 1.23 V,respectively.However,the high potential gap between HER and OER has become a main barrier restricting the large-scale application of this procedure.Electrocatalysisi oxidation of organic compounds with active groups replacing sluggish OER represents an effective pathway toward reducing the potential of water splitting.The conversion potentials driving the conversion of substrates in electrocatalysis oxidation of organics are relatively lower than that of OER,and,meanwhile,more valuable organic chemicals instead of O₂ are produced.This process is thermodynamically favorable and economically attractive.Nevertheless,the existing most of catalysts show low electrocatalytic activities,resulting in that the slightly higher potentials are still required for the oxidation of organics.Thus,the development of efficient electrocatalysts toward reducing the potential of conversion of organic compounds is highly desirable for the practical application of electrolysis water production H₂ with low-cost.In this aspect,Ru-and Co-based catalysts with excellent electrocatalytic activities have been prepared through tuning the structure size and coordination geometry.These catalysts significantly reduce potential of organic substrates conversion and improve the practical application potential toward hydrogen production via electrocatalytic water splitting.And the main work in this thesis includes following three parts:（1）Ru nanoparticles with small size on the surface of nitrogen-doped carbon nanotubes（Ru-NPs/NCNTs）was prepared via a simple impregnation and wet-chemical reduction strategy.The obtained Ru-NPs/NCNTs shows outstanding performance toward electrocatalytic oxidation of benzyl alcohol,achieving the current density of 10m A cm^-2 at 1.19 V vs.RHE,which is much less than that of OER（1.76 V vs.RHE）.Moreover,benzyl alcohol is also converted into benzaldehyde with high yield（96%）and Faraday efficiency（100%）during this process.Furthermore,Ru-NPs/NCNTs also possesses robust stability and its catalytic activity is still maintained after 5 cycels electrocatalysis.Theoretical calculation shows that the good activity of Ru-NPs/NCNTs can be attributed the unique horizontal adsorption geometry between benzyl alcohol and the surface atoms of Ru-NPs,which shortens the distance between the hydroxyl group and the Ru active centers,further increasing the activation opportunity and enhancing the electrocatalytic activity.This work offers a new strategy for developing highly efficient electrocatalysts toward organics oxidation,promoting the anodic reaction kinetics and improving cathodic hydrogen production efficiency.（2）Ru nanoparticles,possessing uniform structure size of 1.3 nm,were anchored on the the surface of nitrogen-doped carbon nanorodes（Ru/CN-Rod）through impregnation and thermal treatment approach.And the structure size and the loading amount of Ru nanoparticles can be effectively modulated by the stragety,simultaneously the electrocatalytic performance was also maintained.As a result,the obtained Ru/CN-Rod reachs the current density of 10 m A cm^-2 at the potential of 1.04V vs.RHE through the electro-oxidation of furfuryl alcohol,and simultaneously promotes the highly selective formation of furfural with the Faraday efficiency of ca.100%.Additionally,Ru/CN-Rod also exhibits ultra-high activity toward HER in alkaline solution,which only requires the overpotential of 56.3 m V achieving the current density of 10 m A cm^-2.And its HER performance can be comparable to commercial 20%Pt/C catalyst（54.2 m V）.Moreover,Ru/CN-Rod shows robust stability activity,which can endure electrolysis for 24 h and 5000 cycles at CV tests.Furthermore,Ru/CN-Rod can also serves as a bifunctional catalyst to achieve 10 m A cm^-2 at 1.42 V in a two-electrode electrolysis system,in which the eleoctro-oxidation of furfuryl alcohol and HER are perfomed at the same tiome.The potential is lower than the overpotential（1.57 V）for the conventional overall water splitting over commercial Pt/C and Ir O₂.This work provides a new strategy for the development of high-efficiency dual-functional electrocatalytic catalysts,as well as the achievement of electrocatalytic oxidation of organics and the electrolysis water.（3）Single-atom Ru loading on N,S co-doped commercial carbon（Ru-SAs/NSC）was obtained through the pyrolysis of Ru-bipyridyl complex.The co-doped strategy can not only effectively prevent the migration of isolated Ru atoms and maintain the rather high loadings of Ru（5.56 wt%）,but also significantly improve the stability and activity of Ru-SAs/NSC.The resulting Ru-SAs/NSC further enhances the electrocatalytic activity of Ru-based catalysts for electro-oxidation of benzyl alcohol,which reaches 10 m A cm^-2 at the potential of 0.97 V vs.RHE.Furthermore,benzaldehyde with high yield（96%）,selectivity（～99%）and Faraday efficiency（100%）can be still achieved.Additionally,we have demonstrated that the adsorption geometry of reactants on surface of catalysts significantly affects the electrocatalytic performance of catalysts via ingeniously tuning the structure of substrates.This work highlights the vital role of adsorption geometry of the substrate molecules in the performance of catalyst toward the exploitation of active electrocatalysts and the design of efficient reactions.（4）Single-atom Co on N,S co-doped carbon（Co-SAs/NSC）was synthesized by the low-temperature pyrolysis of Co-bipyridyl complex.The loadings of Co-SAs/NSC with Co-S₂N₄ geometry is about 10.15 wt%.The Co-SAs/NSC shows excellent activity toward electro-oxidation thioether in acid solution,which achieves the 10 m A cm^-2 at the potential of 1.44 V vs.RHE.At a low potential of 1.40 V vs.RHE,the conversion rate is as high as 99.7%,which is more than those of Pt catalyst and corresponding Co nanoparticles.Additionally,experimental and theoretical calculations shows that single-atom Co as the active center can accurately adsorb with the S-sites of substrate,and promote the transformation of intermediates to products,further reducing the reaction energy barrier and improving the catalytic performance.This work opened up a new way for the fabrication of highly density metal single atom catalysts and the production of valuable products thrgouh the conversion of low value orgiancs.