Review Atomically precise metal nanoclusters for (photo)electroreduction of CO 2 : Recent advances, challenges and opportunities Lubing Qin a , Guanyu Ma a , Likai Wang b , Zhenghua Tang a,c,⇑ a Guangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, Guangdong, China b School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255049, Shandong, China c Guangdong Engineering and Technology Research Center for Surface Chemistry of Energy Materials, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, Guangdong, China article info Article history: Received 30 June 2020 Revised 1 September 2020 Accepted 1 September 2020 Available online 09 September 2020 Keywords: Atomically precise metal nanoclusters (Photo)electroreduction of CO 2 Structure/function relationship Theoretical calculations Advances Opportunities and challenges abstract To alleviate the global warming by removing excess CO 2 and converting them into value-added chemi- cals, (photo)electrochemical reduction has been recognized as a promising strategy. As the CO 2 reduction reaction (CO 2 RR) is involved with multiple electrons and multiple products, plus the complexity of the surface chemical environment of the catalyst, it is extremely challenging to establish the structure/func- tion relationship. Atomically precise metal nanoclusters (NCs), with crystallographically resolved struc- ture, molecule-like characters and strong quantum confinement effects, have been emerging as a new type of catalyst for CO 2 RR, and more importantly, they can provide an ideal platform to unravel the com- prehensive mechanistic insights and establish the structure/function relationship eventually. In this review, the recent advances regarding employing molecular metal NCs with well-defined structure including Au NCs, Au-based alloy NCs, Ag NCs, Cu NCs for CO 2 RR and relevant mechanistic studies are discussed, and the opportunities and challenges are proposed at the end for paving the development of CO 2 RR by using atomically precise metal NCs. Ó 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved. Contents 1. Introduction ......................................................................................................... 360 1.1. The significance and mechanism of (photo)electrochemical CO 2 RR ....................................................... 360 1.2. The advantages of employing atomically precise metal NCs for CO 2 RR .................................................... 361 2. Atomically precise metal NCs for CO 2 RR .................................................................................. 361 2.1. Molecular Au NCs for CO 2 RR ...................................................................................... 361 2.2. Molecular Au-based alloy NCs for CO 2 RR ............................................................................ 366 2.3. Molecular Ag NCs for CO 2 RR....................................................................................... 366 2.4. Molecular copper NCs for CO 2 RR ................................................................................... 368 3. Challenges and opportunities ........................................................................................... 368 Declaration of Competing Interest ....................................................................................... 369 Acknowledgments .................................................................................................... 369 References .......................................................................................................... 369 https://doi.org/10.1016/j.jechem.2020.09.003 2095-4956/Ó 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved. ⇑ Corresponding author at: Guangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, Guangdong, China. E-mail address: zhht@scut.edu.cn (Z. Tang). Journal of Energy Chemistry 57 (2021) 359–370 Contents lists available at ScienceDirect Journal of Energy Chemistry journal homepage: www.elsevier.com/locate/jechem