Study On Transition Metal And Au Coloaded SrTiO₃ To Reduce CO₂ And H₂O Into Syngas Under Visible-light Irradiation

Rapidly increasing consumption of fossil energy and tremendous emission of green-house CO₂ because of industrial and inhabitant need have attracted wide attention.The recycle based on photocatalysis approach to reduce CO₂ into combustible and then burning consumption could help extricate human from dependence of fossil energy.Simulating the natural photosynthesis,this semiconductor-based photochemical route could convert inexhaustible CO₂ and H₂ O into CO,H₂,methanol,methane fuels,which is an ideal approach to transform solar energy to chemical energy and thus to satisfy human's energy demand.Traditional wide-band-gap semiconductors,such as TiO₂,SrTiO₃,etc,exhibit excellent chemical stability and therefore are ideal materials for photocatalytic reaction,but the characteristic of ultravioletexcitation limits the utilization of solar energy.Au nanoparticles?NPs?exhibit intensivevisible-light absorption due to the local surface plasmon resonance?LSPR?effect.If combining Au NPs with SrTiO₃,the photoelectrons excites from the surface of Au can be transferred onto the conduction band of SrTiO₃,and then,is pumped with sufficient potential to participate in CO₂ photoreduction.Based on the above-mentioned mechanism,Au NPswere photodeposited on the commercial SrTiO₃?STO?sample to form Au@STO which successfully achieved CO₂ photoreaction into syngas?the mixture of CO and H₂?and methane under visible-light irradiation.Furthermore,to improve the productivity and the selectivity towards syngas,nine kinds of metal NPs?Pt?Ag?Cu?Ni?Pd?Ru?Rh?Co?Ir?were loaded on Au@STO as cocatalysts.The photocatalytic characterizations indicated that Rh-Au@STO sample exhibited the highest turnover number?TON=17.2?and best selectivity?Sel.=98%?.Compared with Au@STO sample,it achieved 6-times enhancement of photocatalytic productivity and the suppression of CH4 evolution.According to previous study on the chemisorption energy of various gaseous reactants over these metals,it could beproposed that the moderate chemisorption energies towards all the reactants and products helped sample to achieve high efficiency because of the easy adsorption of reactants and easy desorption of products.What's more,in contrast to non-noble metals,such as Ni and Co,the CH4 reforming over noble metals conversed CH4 and CO₂ into syngas,which contributed to the better selectivity for syngas evolution.The corresponding O₂ evolution as oxidation productwas not detected and the CO₂ photoreaction went slower with reaction time prolonging.After detailed characterization,the reason could be ascribed to that the lattice Ti—O—Ti structure of SrTiO₃ was oxidized to Ti—O—O—Ti,leading to impedimentto further oxidizationover the surface of semiconductor.Although the universal defects of no oxidative product and unsustainability in CO₂ photoreduction couldn't be resolved,our study has realized relatively high syngas productivity under visible-light irradiation.This work reports the syngas synthesis via plasmonic photocatalysis for the first time.Compared with the conventional way which relies on the consumption of nature resources,our study provides a low-cost and non-pollution approach.