Rational Design Of Alloyed Catalysts Towards Chemical Reduction Of Carbon-based Moleculars

The development of modern economy relies on the consumption of fossil fuels,such as coal,petroleum,and natural gas.The overuse of fossil fuels resulted in serious energy crisis.The ever-increasing energy demand drives researchers to explore sustainable alternatives,including wind,water,and solar energies.Due to the intermittent and local properties,such renewable energy sources are difficult to merge into the electricity grid.Considering the intermittent thermal energy or electricity powered by renewerable sources,it is highly desired to storage the renewerable energy into chemical energy,which is commonly a chemical reduction process.The electrochemical reduction of CO2 is particularly appealing,because this process proceeds under the ambient reaction condition and can be driven by intermittent electricity produced by renewable energy sources.However,electrochemical reduction of CO2 requires highly efficient catalysts because of the high energy barrier of the C-O activation in CO2 molecular.Developing alloyed materials represents a promising strategy to the design of ideal catalysts,because the alloyed materials usually exhibited distinct properties compared with the single counterparts.Moreover,the ensemble effect and electron transfer in alloyed materials provides additional opportunities to tune the catalytic properties.Therefore,rational design of alloyed systems is a potential means to develop highly efficient catalysts towards electrochemical reduction of CO2.Herein,we reported the controlled synthesis and catalytic properties towards reduction reaction of alloyed systems,including pentacle Au-Cu alloyed nanocrystals,CdSxSe1-2 alloyed nanorods,and NixSn1-xS2 ultrathin nanosheets.These alloyed materials showed superior performance towards model reduction reaction or electrochemical reduction of CO2,We also investigated the influence of alloy effect on the process of CO2 electrochemical reduction.The related projects are concluded as follows:1.We firstly investigated the controlled synthesis and formation mechanism of alloyed materials.The pentacle Au-Cu alloyed nanocrystals which contained abundant high-index facets were synthesized and applied to the model reduction reaction of p-nitrophenol.The growth is found to start from a decahedral core,followed by protrusion of branches along twinning planes.Due to the high-index facets,the pentacle nanocrystals showed better catalytic activity than those of conventional pure Au and Au-Cu alloyed nanoparticles towards the reduction of p-nitrophenol to p-aminophenol by NaBH4.2.We further illustrated the influence of alloy effect on the process of CO2 electrochemical reduction.Alloyed CdSxSe1-x nanorods with tunable Se contents were prepared through the co-reduction of S and Se powders.Such alloyed CdSxSe1-*x nanorods enabled the widest range of syngas proportions ever reported at the current density above 10 mA cm-2 in CO2 electrochemical reduction.At-1.2 V vs RHE,the ratios of CO/H2 in syngas varied from 4:1 to 1:4 with the x value switching from 1 to 0 in CdSxSe1-x nanorods.Notably,all proportions of syngas were achieved with current density higher than-25 mA cm-2.During the potentiostatic tests,CdSxSe1-x nanorods exhibited excellent long-term stability.Mechanistic study revealed that the increased Se content in CdSxSe1-x nanorods strengthened the binding of H atoms,leading to the increased coverage of H*and thus the enhanced selectivity for H2 production in CO2 electrochemical reduction.3.The intrinst factor acconting for the enhancement of alloyed systems in CO2 electrochemical reduction was further revealed.In this part,we alloyed atomically thin SnS2 nanosheets with 1%to 7%of Ni(which also named as Ni doped SnS2)for enhanced performance towards CO2 electroreduction.The Ni doped SnS2 nanosheets exhibited much higher current density and Faradaic efficiency for formate product than that of the pure SnS2 nanosheets.Mechanistic study revealed that Ni doping gave rise to a defect level and lowered the work function of SnS2 nanosheets,resulting in the promoted CO2 activation process and thus improved performance in CO2 electroreduction.