The Performance Of Atomically Precise Au₂₅clusters As Co-catalyst In Photocatalysis

Excessive reliance on fossil fuels has not only led to a surge in greenhouse gas CO₂,but also exacerbated energy shortages.Photocatalytic technology can either convert solar energy into clean energy or reduce CO₂ to CO,CH₄and so on as fuel,which could solve the problem of global warming and energy crisis simultaneously,so this technology has attracted scientists`attention.Different from conventional Au nanoparticles,atomically precise Au nanoclusters?NCs?protected by specific ligands can exhibit molecule-like transition with discrete energy verified by HOMO-LOMO gap contributed to their intriguing size-specific optical,electronic,and catalytic properties.These properties render them versatile materials as both photosensitizer and co-catalyst in solar energy conversion,a subset related to light absorption and subsequent electron transfer reaction involving multiple protons and multiple redox equivalents.However,as a molecular-like catalyst,Au NCs suffer from aggregation attributed to highly reactive oxygen species?e.g.,superoxide radicals and hydroxyl?under light irradiation,resulting in the formation of Au nanoparticles and poor photoactivity.Therefore,sustaining the long-term chemical or photochemical stability of homogenous molecular catalyst remains a significant challenge.In this paper,water-soluble Au₂₅?SG?₁₈?SG=glutathionate?,as a star material,was used as the research object.The bottleneck problem of Au nanocluster aggregation due to the loss of ligand protection was solved by using porous ZIF-8 carrier and Ti O₂ shell as protective layer;the effect of particle size on the reaction performance of Au nanoparticles as photocatalytic catalyst was studied;futhermore,molecular catalyst?Re PH?was introduced to promote charge separation and transfer.In the process of H₂O spiltting to H₂ and CO₂ reduction to CO by dual photoreductive sites,the overall photoelectron utilization was improved.Also,the photocatalytic performance of CO₂ reduction to CO and H₂O spiltting to H₂ was greatly improved by introducing the metal Co ion in the porous Au₂₅?SG?₁₈@ZIF-8 carrier.By adjusting the Co/Zn ratio in the carrier,the total electron utilization rate of the reaction was nearly 10 times higher than that of the original Au₂₅?SG?₁₈@ZIF-8 catalyst,and the H₂/CO ratio in the mixed gas products was also obtained.The specific research contents are as follows:?1?Using Au₂₅?SG?₁₈@ZIF-8 as precursor,an amorphous Ti O₂ shell was synthesized outside ZIF-8 by hydrothermal method.The results of photocatalytic CO₂ reduction and water spiltting of Au NPs@ZIF-8@Ti O₂ showed that the yield of H₂?1577?mol/g/h?of Au₂₅?SG?₁₈@ZIF-8@Ti O₂ was 5 times higher than that of Au NPs@ZIF-8@Ti O₂,and the amount of CO?21?mol/g/h?was increased by three times,revealing the Au nanocluster as a catalyst has higher catalytic reduction performance than Au NPs.In order to further improve the photoelectron utilization,Au₂₅@ZIF-8@Ti O₂-Re P with dual photoreductive sites was prepared by grafting Re PH molecules on the surface of Au₂₅@ZIF-8@Ti O₂.The catalyst showed extremely high photochemical stability with almost invariable production rates of 2245?mol/g/h and 132?mol/g/h for H₂ and CO and overcomed the aggregation of Au₂₅ NCs and the degradation of Re?I?complex.?2?A series of two-dimensional laminated Au₂₅?SG?₁₈@Co/Zn-ZIF-L catalysts with different Co/Zn ratios were obtained by introducing Co ions with catalytic reduction activity in the original Au₂₅?SG?₁₈@ZIF-8 catalyst.By optimizing the content of Co ion,the photoelectron utilization was greatly improved,especially the photocatalytic activity of CO₂ reduction to CO.When the Co content was 1.38 wt%,the photocatalytic activity was the highest with 20.55?mol H₂ and 14.53?mol CO after irradiation for 1 hour under visible light(100 m A·cm^-2).The results also showed that Co/Zn-ZIFs carriers had different CO₂ adsorption properties due to different topological structures,which affected the photocatalytic reaction performance.Two-dimensional laminated Au₂₅?SG?₁₈@Co/Zn-ZIF-L catalysts had higher catalytic performance than three-dimensional dodecahedral Au₂₅?SG?₁₈@Co/Zn-ZIFs.