caoxing

Visible-light-driven conversion of CO₂ into chemical fuels is an intriguing approach to address the energy and environmental challenges. In principle, light harvesting and catalytic reactions can be both optimized by combining the merits of homogeneous and heterogeneous photocatalysts; however, the efficiency of charge transfer between light absorbers and catalytic sites is often too low to limit the overall photocatalytic performance. In this communication, it is reported that the single-atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO₂ conversion, wherein the graphene bridges homogeneous light absorbers with single-atom catalytic sites for the efficient transfer of photoexcited electrons. As a result, the turnover number for CO production reaches a high value of 678 with an unprecedented turnover frequency of 3.77 min⁻¹, superior to those obtained with the state-of-the-art heterogeneous photocatalysts. This work provides fresh insights into the design of catalytic sites toward photocatalytic CO₂ conversion from the angle of single-atom catalysis and highlights the role of charge kinetics in bridging the gap between heterogeneous and homogeneous photocatalysts.

The single-atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO₂ conversion, wherein the graphene bridges homogeneous light absorbers with single-atom catalytic sites for the efficient transfer of photoexcited electrons. This design enables a turnover frequency of 3.77 min⁻¹, superior to those obtained with conventional heterogeneous photocatalysts.

Ever-increasing fossil-fuel combustion along with massive CO₂ emissions has aroused a global energy crisis and climate change. Photocatalytic CO₂ reduction represents a promising strategy for clean, cost-effective, and environmentally friendly conversion of CO₂ into hydrocarbon fuels by utilizing solar energy. This strategy combines the reductive half-reaction of CO₂ conversion with an oxidative half reaction, e.g., H₂O oxidation, to create a carbon-neutral cycle, presenting a viable solution to global energy and environmental problems. There are three pivotal processes in photocatalytic CO₂ conversion: (i) solar-light absorption, (ii) charge separation/migration, and (iii) catalytic CO₂ reduction and H₂O oxidation. While significant progress is made in optimizing the first two processes, much less research is conducted toward enhancing the efficiency of the third step, which requires the presence of cocatalysts. In general, cocatalysts play four important roles: (i) boosting charge separation/transfer, (ii) improving the activity and selectivity of CO₂ reduction, (iii) enhancing the stability of photocatalysts, and (iv) suppressing side or back reactions. Herein, for the first time, all the developed CO₂-reduction cocatalysts for semiconductor-based photocatalytic CO₂ conversion are summarized, and their functions and mechanisms are discussed. Finally, perspectives in this emerging area are provided.

Active and stable CO₂-reduction cocatalysts can obviously enhance the efficiency, selectivity, and stability of semiconductor-based photocatalytic CO₂ reduction. All of the developed CO₂-reduction cocatalysts are summarized, and their functions and insightful mechanisms are discussed. This can pave new avenues to the exploration of novel highly active and selective cocatalysts, toward high-performance solar fuel production.

In article number 1702928, Indrajit Shown, Li-Chyong Chen, Kuei-Hsien Chen, and co-workers report a black titania with dual active sites (Ni-nanoclusters and oxygen vacancy) for photocatalytic carbon dioxide (CO₂) reduction via artificial photosynthesis with H₂O and simulated sunlight. The intentionally introduced dual active sites lead to not only high photocatalytic activity, but also to selective solar fuel production under simulated solar light. The CO₂ adsorption and activation capability of the catalyst is demonstrated using computational study and the underlying mechanism in charge transfer and product formation is highlighted.