A novel synergetic effect between Ru and Cu nanoparticles for Ru-Cu/Al2O3 causes highly efficient photothermocatalytic CO2 reduction with good durability

Abstract

Nanocomposites of Ru and Cu nanoparticles co-supported on Al2O3 with different Ru loadings were prepared. The Ru-Cu/Al2O3 nanocomposites well integrates excellent thermocatalytic activity of Ru nanoparticles with efficient photothermal conversion of Cu nanoparticles due to their strong surface plasmonic absorption. They show very high catalytic activity for photothermocatalytic CO2 reduction by methane (CRM) under focused illumination from a 500 W Xe lamp. Very high production rates of H2 (rH2) and CO (rCO) (59.24 and 63.91 mmol min−1 g−1) and light-to-fuel efficiency (η, 33.1%) are acquired under focused UV–vis-IR illumination. Even under focused λ > 560 nm vis-IR illumination, a very high η of 29.2% is acquired. The nanocomposites show very good photothermocatalytic durability due to the side-reactions of carbon deposition being blocked, while a reference catalyst of Cu nanoparticles supported on Al2O3 (Cu/Al2O3) quickly loses photothermocatalytic activity due to severe carbon deposition on Cu nanoparticles. A novel synergetic effect between Ru and Cu nanoparticles for Ru-Cu/Al2O3 is found to block the severe carbon deposition on Cu nanoparticles, thus tremendously promoting photothermocatalytic durability. This is ascribed to the oxidation of carbon species on Cu nanoparticles being accelerated by oxygen species (formed by CO2 dissociation) migrated from Ru nanoparticles. A novel photoactivation is found to substantially promote light-driven thermocatalytic CRM on Ru-Cu/Al2O3 due to the apparent activation energy being immensely reduced upon the focused illumination. This is associated with the rate determining step of the oxidation of carbon species by oxygen species for CRM on Ru-Cu/Al2O3 being accelerated upon the focused illumination.