Ag/Ag2SO3 plasmonic catalysts with high activity and stability for CO2 reduction with water vapor under visible light.

The conversion of CO2 into useful raw materials for fuels and chemicals by solar energy is described using a plasmonic photocatalyst comprised of Ag supported on Ag2SO3 (Ag/Ag2SO3) fabricated by a facile solid-state ion-exchange method and subsequent reduction with hydrazine hydrate. The optimum molar ratio of Ag(0)/Ag(+) was 5 %. Visible light irradiation (>400 nm) of the Ag/Ag2SO3 powder in the presence of CO2 and water vapor led to the formation of CH4 and CO with a quantum yield of 0.126 %, and an energy returned on energy invested of 0.156 %. The Ag/Ag2SO3 retained high catalytic activity after ten successive experimental cycles. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy with energy-dispersive X-ray analysis, UV/Vis absorption spectroscopy, and Brunauer-Emmett-Teller analyses, as well as photocurrent action spectroscopy. It is proposed that the photocatalytic activity of the catalysts is initiated by energy conversion from incident photons to localized surface plasmon resonance oscillations of silver nanoparticles. This plasmonic energy is transferred to the Ag2SO3 by direct electron transfer and/or resonant energy transfer, causing the separation of photogenerated electron/hole pairs.