Abstract
We demonstrated photocatalytic CO2 reduction using water as an electron donor under visible light irradiation by a Z-scheme photocatalyst and a photoelectrochemical cell using bare (CuGa)0.5ZnS2 prepared by a flux method as a CO2-reducing photocatalyst. The Z-scheme system employing the bare (CuGa)0.5ZnS2 photocatalyst and RGO-(CoOx/BiVO4) as an O2-evolving photocatalyst produced CO of a CO2 reduction product accompanied by H2 and O2 in a simple suspension system without any additives under visible light irradiation and 1 atm of CO2. When a basic salt (i.e., NaHCO3, NaOH, etc.) was added into the reactant solution (H2O + CO2), the CO formation rate and the CO selectivity increased. The same effect of the basic salt was observed for sacrificial CO2 reduction using SO32– as an electron donor over the bare (CuGa)0.5ZnS2 photocatalyst. The selectivity for the CO formation of the Z-schematic CO2 reduction reached 10–20% in the presence of the basic salt even in an aqueous solution and without loading any cocatalysts on the (CuGa)0.5ZnS2 metal sulfide photocatalyst. It is notable that CO was obtained accompanied by reasonable O2 evolution, indicating that water was an electron donor for the CO2 reduction. Moreover, the present Z-scheme system also showed activity for solar CO2 reduction using water as an electron donor. The bare (CuGa)0.5ZnS2 powder loaded on an FTO glass was also used as a photocathode for CO2 reduction under visible light irradiation. CO and H2 were obtained on the photocathode with 20% and 80% Faradaic efficiencies at 0.1 V vs RHE, respectively.
Highlights
Beneficial CO2 fixation technology especially utilizing renewable energy is strongly demanded to solve resources, energy, and environmental issues
We have successfully constructed a Z-schematic CO2 reduction system using water as an electron donor employing bare CuGaS2 as a CO2reducing photocatalyst combined with CoOx/BiVO4 as an O2evolving photocatalyst and reduced graphene oxide (RGO) as a solid-state electron mediator driven via interparticle electron transfer (Figure 1(b)).[12]
We demonstrated Z-schematic CO2 reduction using bare (CuGa)0.5ZnS2 prepared by a flux method and RGO-(CoOx/BiVO4) using water as an electron donor under visible light irradiation in the presence of various salts as shown in Figure 1(b) as an artificial photosynthesis
Summary
Schematic CO2 reduction reached 10−20% in the presence of the basic salt even in an aqueous solution and without loading any cocatalysts on the (CuGa)0.5ZnS2 metal sulfide photocatalyst. It is notable that CO was obtained accompanied by reasonable O2 evolution, indicating that water was an electron donor for the CO2 reduction. The present Z-scheme system showed activity for solar CO2 reduction using water as an electron donor. The bare (CuGa)0.5ZnS2 powder loaded on an FTO glass was used as a photocathode for CO2 reduction under visible light irradiation. CO and H2 were obtained on the photocathode with 20%. 80% Faradaic efficiencies at 0.1 V vs RHE, respectively
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