Doping engineering in S–scheme composite for Regulating the selectivity of photocatalytic CO2 reduction

Regulating product selectivity in photocatalytic CO2 reduction to enhance the yield of valuable hydrocarbons remains a formidable challenge because of the diversity of reduction products and the competitive reduction of H2O. Herein, ultrathin Bi2O3/ Co–doped SrBi4Ti4O15 S–scheme photocatalysts (Co–BS) were synthesized using a hydrothermal method. The Bi2O3/Co–doped SrBi4Ti4O15 photocatalyst exhibited significantly higher selectivity for CH4 (62.3 μmolg−1) and CH3OH (54.1 μmolg−1) in CO2 reduction compared with pure SrBi4Ti4O15 (27.2 and 0.8 μmolg−1) and the Bi2O3/SrBi4Ti4O15 S–scheme without Co (30.2 and 0 μmolg−1). The experimental results demonstrated that the inclusion of Co into SrBi4Ti4O15 expanded the range of light absorption and generated an internal electric field between Co–doped SrBi4Ti4O15 and Bi2O3. Density functional theory calculations and other experimental findings confirmed the formation of a new doping energy level in the Bi2O3/SrBi4Ti4O15 S–scheme heterojunction after Co doping. The valence band electrons of Bi2O3/SrBi4Ti4O15 transitioned to the Co–doped level because of the interconversion between Co3+ and Co2+ under the action of the internal electric field. Furthermore, the corresponding characterizations revealed that the adsorption and electron transfer rates of the surface active sites were accelerated after Co doping, enhancing electron involvement in the photocatalytic reaction process. This study presented a metal–doped S–scheme heterojunction approach for CO2 reduction to produce high–value products, enhancing the conversion of solar energy into energy resources.