The Preparation Of Strongly Light Absorptive And Well Dispersed Metal Catalysts For Photothermal Hydrogenation Of Carbon Dioxide

Since the industrial revolution,the excessive use of fossil fuels has caused serious problems such as energy shortage and global warming,bringing challenges to the sustainable development of human society.To this end,the conversion of solar energy into chemical energy through photocatalytic carbon dioxide reduction provides a promising solution to these global challenges.Among different photocatalytic processes,photothermal hydrogenation of carbon dioxide has attracted increasing attention due to its high efficiency of solar energy utilization.Despite recent progresses,existing photothermal catalysts still suffer from insufficient light absorption ability across the entire solar spectrum,limiting the further improvement of the solar-to-chemical energy conversion efficiency.The light absorption ability can be improved by increasing the metal loading but often at the expense of decreasing the metal dispersity.Therefore,it is of emerging interest to develop new strategies for the preparation of highly loaded and well dispersed metal catalysts for efficient photothermal CO2 catalysis.In this thesis,we aimed to address the above-mentioned challenge and carried out the following studies:(1)We developed an ion-exchange route to supported Ru nanoparticles with both high loadings and dispersity.This two-step strategy involved the ion-exchange reaction between Ru3+and Mg(OH)2 to form uniformly distributed and chemically bonded Ru precursors on Mg(OH)2 supports,followed by the subsequent low-temperature reduction by H2 to produce highly dispersed Ru nanoparticles whose sizes barely change as the loading increases.Detailed characterizations of the catalyst morphology revealed the effectiveness of this ion-exchange strategy in the preparation of highly loaded and well dispersed Ru catalysts.By controlling the metal loading and reduction temperature,Ru nanocatalysts with strong sunlight absorption ability and high dispersity were obtained,enabling the optimization of the photothermal catalytic performance.(2)Although precious metal catalysts such as Ru exhibits high catalytic activity,their widespread applications are limited by the high cost.In an attempt to reduce the cost of catalysts for photothermal hydrogenation of carbon dioxide,we tried to extend above strategy to the preparation of strongly light absorptive and well dispersed non-noble metal catalysts.We firstly prepared nickel catalysts supported on the Mg(OH)2 support through the same process.The dispersity of as-obtained Ni catalysts was lower than expected,which could be traced to the higher reduction temperature than Ru.We further addressed this issue by coating a layer of silica on the Mg(OH)2 support.Thanks to the adsorption and spatial confinement of the SiO2 structure,we successfully prepared high loaded and well dispersed Ni catalysts.With greatly improved light absorption ability and high metal dispersity,the as-obtained Ni catalyst exhibited excellent performance in photothermal hydrogenation of carbon dioxide.Our study provides an avenue for the preparation of strongly light-absorptive and highly dispersed metal catalysts for efficient conversion of carbon dioxide into solar fuels.