Design of PdAu alloy plasmonic nanoparticles for improved catalytic performance in CO2 reduction with visible light irradiation

Photo-catalytically reducing CO2 into valuable compounds is beneficial for both relieving the fossil fuel crisis and protecting the environment, and has become one of the hotspots in photocatalytic area recently. In this research, earth-abundant natural gas was adopted as the reductant, and visible light assisted CO2 reduction with methane (CRM) was selected as the probe reaction. The alloys between a group 8 metal and a group 11 element, PdAu alloy in this case, were developed as catalysts. It is found that, by increasing the content of Au in the PdxAuy alloys, the electronic structure of Pd could be gradually tuned to electron deficient, which favored the stability of the PdxAuy/Al2O3 catalysts in thermal-driven CRM with partially reduced activities. Meanwhile, the plasmonic absorption in visible light region and the electromagnetic field induced by hot electrons were enhanced in Au-containing PdxAuy alloys, which facilitated CO2 activation to oxygen radical and was regarded to be responsible for further accelerating the reaction rate with visible light irradiation. At the same time, the electronic structure and the stability of the catalysts remained nearly uninfluenced with extra light irradiation. With the co-assistance of electronic structure and plasmonic property of PdxAuy alloys, the stability of Pd90Au10/Al2O3 catalyst was effectively improved and the activity was not sacrificed compared with the reference Pd/Al2O3. The stability improvement strategy achieved in this work, together with the enhanced reactant activation capacity of group 11 elements, offers an avenue to synthesize catalysts with both enhanced catalytic stability and activity with visible light irradiation. This study provides promising approach for applying alloys in photo-driven or photo-assisted reaction systems.