Abstract
A visible-light-driven Z-scheme photocatalytic CO2 reduction reaction (CO2RR) to produce CO was demonstrated using an aqueous particulate dispersion containing two bare semiconductors, (CuGa)_(0.3)Zn_(1.4)S2 for CO2RR and BiVO4 for water oxidation. The semiconductors were mixed with a water-soluble cobalt tris(dimethylbipyridine) complex. The CO selectivity was 98% (against H2), and the rate of CO generation was 1-2 orders of magnitude higher than those of previously-reported aqueous suspension photocatalytic systems. O2 was continuously evolved, and isotope tracer analyses confirmed that CO2 was the carbon source for CO. Experimental studies and calculations suggest that the Co complex acts dual-functionally in synergy with (CuGa)_(0.3)Zn_(1.4)S2 and BiVO4: it behaves as an efficient ionic electron mediator, and also acts as a new active CO2RR cocatalyst after a structural change by accepting photoexcited electrons from (CuGa)_(0.3)Zn_(1.4)S2. This simple method, operating in a self-optimizing manner in solution, has great potential to help achieve sustainable, highly active artificial photo-synthetic systems.
NSTL