Tunable green syngas generation from CO(2) and H(2)O with sunlight as the only energy input

The carbon-neutral synthesis of syngas from CO(2) and H(2)O powered by solar energy holds grand promise for solving critical issues such as global warming and the energy crisis. Here we report photochemical reduction of CO(2) with H(2)O into syngas using core/shell Au@Cr(2)O(3) dual cocatalyst–decorated multistacked InGaN/GaN nanowires (NWs) with sunlight as the only energy input. First-principle density functional theory calculations revealed that Au and Cr(2)O(3) are synergetic in deforming the linear CO(2) molecule to a bent state with an O-C-O angle of 116.5°, thus significantly reducing the energy barrier of CO(2)RR compared with that over a single component of Au or Cr(2)O(3). Hydrogen evolution reaction was promoted by the same cocatalyst simultaneously. By combining the cooperative catalytic properties of Au@Cr(2)O(3) with the distinguished optoelectronic virtues of the multistacked InGaN NW semiconductor, the developed photocatalyst demonstrated high syngas activity of 1.08 mol/g(cat)/h with widely tunable H(2)/CO ratios between 1.6 and 9.2 under concentrated solar light illumination. Nearly stoichiometric oxygen was evolved from water splitting at a rate of 0.57 mol/g(cat)/h, and isotopic testing confirmed that syngas originated from CO(2)RR. The solar-to-syngas energy efficiency approached 0.89% during overall CO(2) reduction coupled with water splitting. The work paves a way for carbon-neutral synthesis of syngas with the sole inputs of CO(2), H(2)O, and solar light.