Study On The Dynamic Reaction Process In Catalytic Conversion Of Carbon-based Small Molecules

Efficient conversion of carbon-based small molecules,such as carbon dioxide and methane,is of great significance to the security of environment and energy in China.Realizing the efficient utilization of carbon-based small molecules requires catalysts with high activity,selectivity,and stability,together with efficient and sustainable catalytic process.During the reaction process,catalysts do not usually stay at a static state.They are often involved in the process based on reversible redox reactions.It is an important part of catalysis research to clarify the redox reactions that take place on the surface of the catalyst,ensure the reproducibility of the catalytic active sites,and build a stable and efficient catalytic cycle.In this paper,based on a variety of in situ characterization methods,we took an in-depth study on the dynamic redox process on the surface of the catalyst in the carbon dioxide reduction and alkane oxidation system.We developed a variety of effective methods such as atomic structure regulation and external field introduction to ensure the regeneration of highly active sites.With the development of advanced catalysts and sufficient tuning of the surface redox properties,we successfully realized facile activation and conversion of CO2,CH4,and C3H8 molecules.Three systems studied are listed as follows:1.Achieving efficient and sustainable dissociation of carbon dioxide molecules via reversible redox process.We found that carbon dioxide can be directly dissociated into adsorbed carbon monoxide and adsorbed oxygen species over PdFe alloy catalyst.However,the adsorbed oxygen species on the surface of disordered alloy catalyst cannot be reduced,thus hindering further dissociation.To solve the problem,an intermetallic compound catalyst with ordered arrangement of Pd and Fe atoms was constructed,where the adsorbed oxygen species could be rapidly reduced and desorbed,thus ensuring the reproducibility of the catalytic site and realizing the sustainable dissociation process.2.Achieving efficient and sustainable transformation of methane molecules via irradiation introduction.We developed Au1/BP catalyst for methane selective oxidation from the perspective of oxygen activation,which is inspired by our work in section 1.Active P=O species forms after the oxygen dissociation process,which can induce the activation and dehydrogenation of methane.The Au single atoms provide sites for the adsorption of methyl species.However,steric hindrance between the formed methyl and hydroxyl groups blocks their combination to produce methanol.To solve this problem,we introduced irradiation as a driving force,which enabled water to participate into the activation process of oxygen.The produced hydroxyl radicals from water and oxygen can break the steric hindrance,and promote the further conversion of methyl species to methanol.3.Achieving propane-to-methanol conversion under mild conditions via a water mediated oxidation path.Gas phase oxidation of propane usually generates CO2 and CO as main products over VOx/Al2O3 catalyst,rendering it a great challenge to achieve mild conversion of propane to value-added liquid products.Inspired by the work in section 2,we introduced water as an reactant into the oxidation process.It is found that water can directly react with oxygen on the surface of the catalyst and form active hydroxyl species,facilitating the activation of propane molecules and methanol production with high selectivity at a low temperature.