Toward high-selectivity CO2 photoelectroreduction: mechanistic foundations, recent advances and challenges

Abstract

Photoelectrochemical carbon dioxide reduction reaction (PEC CO₂RR) is a promising strategy for converting CO₂ into high-value chemicals that contribute to carbon neutrality. However, CO₂ reduction is often accompanied by various competitive reaction pathways in the actual reaction process, which may generate a variety of products. The selective regulation of different products not only directly affects the yield and separation cost of the target product, but also influences the energy efficiency and economic feasibility of the whole process. Improving product selectivity is essential for increasing product yield and understanding the reaction mechanism. This review systematically summarizes recent advances and challenges in achieving high selectivity in PEC CO₂RR. First, the basic concept and principle of the PEC CO₂RR are summarized. Next, the key factors affecting product selectivity are discussed, including catalyst design (catalyst type, modification, composition, and morphology), reaction conditions (applied voltage, light intensity and wavelength, reaction temperature, and electrolyte type) and reactor design (photoelectrode area, synergistic oxidation effect, geometric structure, and gas diffusion electrode). In addition, kinetic and thermodynamic aspects such as the CO₂ adsorption model, band gap structure, and reaction free energy are also explored. Then, the research progress over the past five years on different products is described in detail, focusing on the current status and challenges in the study of C₁ products and C₂ products. Subsequently, the primary factors leading to the failure of PEC CO₂RR are summarized, and various cooperative strategies are introduced to achieve long-term stability in product selectivity. Finally, the challenges and future directions for developing PEC CO₂RR systems with enhanced selectivity are introduced. In particular, the importance of innovative catalyst design, reaction stability, reaction environment optimization, advanced equipment structure and reaction mechanism analysis for promoting PEC CO₂RR in industrial applications is emphasized.