Strategies for Optimizing the Efficiency and Selectivity of Photocatalytic Aqueous CO2 Reduction: Catalyst Design and Operating Conditions

Photocatalytic carbon dioxide (CO₂) reduction (CO₂R) technology towards carbon neutrality is a green and sustainable method to produce carbonous feedstocks (e.g., methane, ethanol, acetic acid). However, the relatively low CO₂R efficiency and unsatisfactory selectivity towards target products hinder its scale-up implementation. Photocatalysts and operating conditions are pivotal in tuning the catalytic environment and governing CO₂R activity. Herein, the photocatalytic CO₂R mechanism and conversion pathways for main C₁/C₂/C₃ products are elaborated. Then, the recent advances in promoting CO₂ photoreduction efficiency and selectivity are summarized and discussed, paying special attention to the catalyst design approaches (defect design and interfacing engineering), as well as the operating conditions (e.g., light intensity and wavelength, pH, CO₂ pressure/concentration, solvent volume, dissolved oxygen, and coexisting ions) which directly affect the catalytic environment. Future researches on photocatalytic CO₂R are proposed in terms of efficient catalyst design, intrinsic transformation mechanism, and sustainable application-oriented CO₂R technologies. The insights obtained will advance our mechanistic understanding of regulating CO₂R pathways, and help drive the adoption of sustainable and highly efficient strategies for producing desired products.