Bismuth Cocatalyst Promotes Selective CO<sub>2</sub> Photoreduction on Defective α-Ga<sub>2</sub>O<sub>3</sub>
Peng Chen, Kanglu Li, Lvcun Chen, Wendong Zhang, Ying Zhou, Fan Dong, Yanjuan Sun
Abstract
Photocatalytic CO 2 reduction (PCR) can convert solar energy into chemicals, fuels, and feedstocks, but is limited by the deficiencies of photocatalysts in controlling photon-to-electron transformation and activating CO 2 molecules, thus leading to an insufficient yield and selectivity. Here, we synthesized α-Ga 2 O 3 with oxygen vacancies (OVs) as local active sites for regulating the light absorption and charge carrier transmission. However, the photoexcited protons are inclined to enable H 2 formation at the OVs, resulting in the deterioration of the selectivity of PCR. Therefore, we further used chemical reduction to deposit the cocatalyst of bismuth nanoparticles (Bi NPs) on the surface of α-Ga 2 O 3 to construct a new synergistic Bi-OV active center. The active structure can significantly enhance the CO 2 adsorption and activation. Due to the weak intrinsic hydrogen adsorption capacity of Bi NPs with the large free energy barrier for the H* formation, effective inhibition of the H 2 evolution can be achieved. Simultaneously, the free energy barrier of intermediate CH 2 * formation becomes higher on Bi-OV sites, making the formation of CH 4 difficult. Thus, the Bi-OV synergistic active center can favorably inhibit H 2 evolution and highly improve the conversion efficiency and selectivity of CO 2 -to-CO. The concept of combination of a metal cocatalyst with oxygen vacancy in simultaneously promoting activity and selectivity could be extended to diverse catalysis systems.