Atomic‐Level Reactive Sites for Semiconductor‐Based Photocatalytic CO₂ Reduction

Abstract

Photocatalytic CO2 reduction is an effective means to generate renewable energy. It involves redox reactions, reduction of CO2 and oxidation of water, that leads to the production of solar fuel. Significant research effort has therefore been made to develop inexpensive and practically sustainable semiconductor‐based photocatalysts. The exploration of atomic‐level active sites on the surface of semiconductors can result in an improved understanding of the mechanism of CO2 photoreduction. This can be applied to the design and synthesis of efficient photocatalysts. In this review, atomic‐level reactive sites are classified into four types: vacancies, single atoms, surface functional groups, and frustrated Lewis pairs (FLPs). These different photocatalytic reactive sites are shown to have varied affinity to reactants, intermediates, and products. This changes pathways for CO2 reduction and significantly impacts catalytic activity and selectivity. The design of a photocatalyst from an atomic‐level perspective can therefore be used to maximize atomic utilization efficiency and lead to a high selectivity. The prospects for fabrication of effective photocatalysts based on an in‐depth understanding are highlighted.

POM‐Incorporated CoO Nanowires for Enhanced Photocatalytic Syngas Production from CO2

“…As demonstrated broadly in previous reports, the three key factors of an enhanced photocatalyst are broad visible-light absorption, facilitated charge-separation-transportation efficiency, and improved surface catalytic activity. [13,32,33] Accordingly, we find that both morphological and structural devisal are essential for a high-performance catalyst. The ultrathin size would benefit the charge-hole separation and transportation process, while ingeniously designed amorphous structure and chemical composition would result in the high catalytic performance and optimized energy level.…”

Carbon–Graphitic Carbon Nitride Hybrids for Heterogeneous Photocatalysis

“…[ 34,115 ] In these cases, the strong chemical‐bonding ability lowers the energy barrier for intramolecular charge transfer over the metal‐free carbon‐induced photocatalysts. [ 116 ] And reactant adsorption configuration, such as CO 2 and NH 3 , could be highly anchored and immobilized through the near‐field functional groups.…”

Hollow Structure for Photocatalytic CO2 Reduction

“…It is also noticed that most of the CO 2 RRs have a reduction potential within the range of −0.2∼−0.6 V. The little thermodynamic difference makes the product selectivity a great challenge in CO 2 conversion process . Moreover, most of the CO 2 RR process holds a reduction potential close to the hydrogen evolution reaction (HER), which makes the HER a major competitive reaction during the photocatalysis process …”

“…Especially, when taken water as the hole consumption molecule, the overall CO 2 RR can be viewed as an artificial photosynthesis mimicking the natural process . In some cases, hole sacrificial reagents are applied to eliminate the kinetic limitation of the oxidation reaction . Nonetheless in any case, it should ensure that the electrons and holes are consuming in a stoichiometric ratio and the product of CO 2 RR should originate from CO 2 and not from other carbon sources…”