Cobalt-Based Cocatalysts for Photocatalytic CO₂ Reduction

Abstract

Conversion of carbon dioxide (CO₂) into valuable chemicals and renewable fuels via photocatalysis represents an eco-friendly route to achieve the goal of carbon neutralization. Although various types of semiconductor materials have been intensively explored, some severe issues, such as rapid charge recombination and sluggish redox reaction kinetics, remain. In this regard, cocatalyst modification by trapping charges and boosting surface reactions is one of the most efficient strategies to improve the efficiency of semiconductor photocatalysts. This review focuses on recent advances in CO₂ photoreduction over cost-effective and earth-abundant cobalt (Co)-based cocatalysts, which are competitive candidates of noble metals for practical applications. First, the functions of Co-based cocatalysts for promoting photocatalytic CO₂ reduction are briefly discussed. Then, different kinds of Co-based cocatalysts, including cobalt oxides and hydroxides, cobalt nitrides and phosphides, cobalt sulfides and selenides, Co single-atom, and Co-based metal–organic frameworks (MOFs), are summarized. The underlying mechanisms of these Co-based cocatalysts for facilitating CO₂ adsorption–activation, boosting charge separation, and modulating intermediate formation are discussed in detail based on experimental characterizations and density functional theory calculations. In addition, the suppression of the competing hydrogen evolution reaction using Co-based cocatalysts to promote the product selectivity of CO₂ reduction is highlighted in some selected examples. Finally, the challenges and future perspectives on constructing more efficient Co-based cocatalysts for practical applications are proposed.

Keywords

Cobalt-based materials / Cocatalyst / Photocatalysis / CO₂ reduction / Solar energy conversion

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