Surface-Integrating Oxygen Vacancy and CuxO Nanodots Enabling Synergistic Electric Field and Dual Catalytic Sites Boosting CO2 Photoreduction.

High carrier separation efficiency and rapid surface catalytic reaction are crucial for enhancing catalytic CO2 photoreduction reaction. Herein, integrated surface decoration strategy with oxygen vacancies (Ov) and anchoring CuxO (1 < x < 2) nanodots below 10 nm is realized on Bi2MoO6 for promoting CO2 photoreduction performance. The charge interaction between Ov and anchored CuxO enables the formation of enhanced internal electric field, which provides a strong driving force for accelerating the separation of photocharge carriers on the surface of Bi2MoO6 (ηsurf ≈71%). They can also cooperatively reduce the surface work function of Bi2MoO6, facilitating the migration of carrier to the surface. Meanwhile, surface-integrated Ov and CuxO nanodots allowing dual catalytic sites strengthens the adsorption and activation CO2 into *CO2 over Bi2MoO6, considerably boosting the progression of CO2 conversion process. In the absence of co-catalyst or sacrificial agent, Bi2MoO6 with Ov and CuxO nanodots achieves a photocatalytic CO generation rate of 12.75 µmol g-1 h-1, a remarkable increase of over ≈15 times that of the original counterpart. This work provides a new idea for governing charge movement behaviors and catalytic reaction thermodynamics on the basis of synergistic improvement of electric field and active sites by coupling of the internal defects and external species.

A ball milling method for highly dispersed Ni atoms on g-C3N4 to boost CO2 photoreduction.

Atomically dispersed active sites can effectively enhance the catalytic activity, but the synthesis of highly dispersed single-atom active sites remains challenging. Herein, we report for the fabrication of single-atom Ni on g-C3N4 (CN) catalysts for photocatalytic CO2 reduction reaction (CO2RR) using a high-energy ball milling method. The uniformly loaded single-atomic Ni on the surface of the substrate suggests the improvement of synthetic methods. After optimizing the Ni loading, the photocatalyst containing 0.5 at% (0.32 wt%) single-atomic Ni (Ni/CN-0.5) exhibited the highest CO2 reduction performance (∼19.9 µmol·g-1·h-1) without any co-catalyst or sacrificial agent. As visualized by aberration-corrected high-angle annular darkfield scanning transmission electron microscopy (AC HAADF-STEM), the Ni atoms in the Ni/CN-0.5 photocatalyst are most uniformly dispersed for different loadings (0.1, 0.3, 0.5, 0.7, 1.0, 3.0 and 5.0 at%). These results suggest that the uniformity of the single-atom active sites plays a decisive role rather than the loading amount in the highly enhanced performance. This work provides insight into the design of photocatalysts with highly dispersed single-atom catalytic active sites for enhancing activity.