Nano-carbon Based Materials For Electrochemical Reduction Reaction(ORR/ECR/NRR)

Sustainable development is a vital theme of human survival in the 21st century.However,with the progress of science and technology and the development of the society,the human demand for energy is increasing.Thus,the exploration and development of high-performance catalytic materials is a tough task of the current science and technology for researchers.Electrochemical catalytic conversion not only has the advantages of simple operation,mild reaction controlled and reaction,and it can utilize green energy such as nuclear power,wind power and solar energy.As the important component of the electrochemical catalytic conversion,electrochemical reduction reaction includes the oxygen reduction reaction(ORR),carbon dioxide reduction reaction(CO2RR)and nitrogen reduction reaction(NRR).However,the above reaction process involves the multi-step with electronic proton reaction,resulting in slow reaction rate.Therefore,in order to solve the above problems,the choice of the catalyst and design become a crucial question.So far,in view of the electrochemical reduction of clean energy conversion process,reported the main catalysts are the precious metal based catalysts.Looking for a kind of high catalytic efficiency,rich in natural resources,good stability and low cost of alternative catalyst have become the pressing needs in the electrochemical reduction reaction.Nano carbon material has good conductivity,diverse hybrid structure,varied topography and plentiful in resources,thus caused wide attention from scientists.Especially,since 2004,professor Geim and professor Novoselov from the university of Manchester firstly isolated the single layer graphene by means of the micro mechanical exfoliation.Graphene has the novel physical and chemical properties,which is widely appied in the field of catalysis,effect tube,optoelectronic devices,topological insulators as well as the energy storages.For this thesis,the mainly contents are as following:1.Exfoliation of grahene and graphene analogue materials by secondary flow reactors.Mono-and few-layer graphene are achieved in only 75s;By secondary flow reactor,sub 8 nm Fe3O4 nanoparticle loaded few layer graphene can be systhezied without protector;2.Nitrogen doping of graphene oxide was demonstrated for the first time at a temperature as low as 5 0C in ammonia solution with the aid of ultrasonication.Controlling the ultrasonication time and bath temperature permitted tuning of the N doping level.The resulting N doped graphene oxide showed high activity towards the oxygen reduction reaction;3.Designing highly selective and energy-efficient electrocatalysts to minimize the competitive hydrogen evolution reaction in electrochemical reduction of aqueous CO2 remains a challenge.In this study,we report that doping of Pd with a small amount of Te could selectively convert CO2 to CO with a low overpotential.The PdTe/few-layer graphene(FLG)catalyst with a Pd/Te molar ratio of 1:0.05 displayed a maximum CO Faradaic efficiency of about 90%at-0.8 V(vs.reversible hydrogen electrode,RHE),CO partial current density of 4.4 tA cm-2 and CO formation turnover frequency of 0.14 s-1 at-1.0 V(vs.RHE),which were 3.7-,4.3-,and 10-fold higher than that over Pd/FLG,respectively.Density functional calculations showed that Te adatoms preferentially bind at terrace sites of Pd,thereby suppressing undesired hydrogen evolution,whereas CO2 adsorption and activation occurred on the high index sites of Pd to produce CO;4.Nitrogen fixation at ambient conditions remains a significant challenge.In this work,we report nitrogen fixation by Ru single-atom electrocatalytic reduction at room temperature and atmospheric pressure.In contrast to traditional Ru nanoparticles,the single Ru sites supported on ZrO2/N-doped porous carbon greatly promoted electroreduction of aqueous N2 selectively to NH3,affording an NH3 faradaic efficiency of about 21%at a very low overpotential(0.206 V),which significantly surpasses other reported catalysts.An unprecedented NH3 formation rate of 4560μg h-1 mg-1Ru was achieved at-0.21 V versus a reversible hydrogen electrode with stable behavior for at least 60 h of reaction,even comparable to the yields and efficiencies obtained under harsh temperatures and/or pressures.Experiments combined with density functional calculations showed that the Ru sites with oxygen vacancies were major active centres that permit the stabilization of*NNH,the dramatic destabilization of*H,and enhanced N2 adsorption.