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The processes of photocatalytic CO2 reduction (pCO2R) and electrochemical CO2 reduction (ECO2R) have attracted considerable interest owing to their high potential to address many environmental and energy-related issues. In this aspect, a single Cu atom decorated on a carbon nitride (CN) surface (Cu–CN) has gained increasing popularity because of its unique advantages, such as excellent atom utilization and ultrahigh catalytic activity. CN—particularly graphitic CN (g-C3N4)—is a photo- and electrocatalyst and used as an important support material for single Cu atom-based catalysts. These key functions of Cu–CN-based catalysts can improve the catalytic performance and stability in the pCO2R and ECO2R during the application process. In this review, we focus on Cu as a single metal atom decorated on CN for efficient photoelectrochemical CO2 reduction (pECO2R), where ECO2R increases the electrocatalytic active area and promotes electron transfer, while pCO2R enhances the surface redox reaction by efficiently using photogenerated charges and offering integral activity as well as an active interface between Cu and CN. Interactions of single Cu atom-based photo-, electro-, and photoelectrochemical catalysts with g-C3N4 are discussed. Moreover, for a deeper understanding of the history of the development of pCO2R and ECO2R, the basics of CO2 reduction, including pCO2R and ECO2R over g-C3N4, as well as the structural composition, characterization, unique design, and mechanism of a single atom site are reviewed in detail. Finally, some future prospects and key challenges are discussed.

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Copper as a single metal atom based photo-, electro-, and photoelectrochemical catalyst decorated on carbon nitride surface for efficient CO2 reduction: A review

Show Author's information Lulu Li1,§Israr Masood ul Hasan1,3,§ Farwa1,3Ruinan He1Luwei Peng1Nengneng Xu1Nabeel Khan Niazi3( )Jia-Nan Zhang4( )Jinli Qiao1,2( )
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Faisalabad 38040, Pakistan
College of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China

§ Lulu Li and Israr Masood ul Hasan contributed equally to this work.


The processes of photocatalytic CO2 reduction (pCO2R) and electrochemical CO2 reduction (ECO2R) have attracted considerable interest owing to their high potential to address many environmental and energy-related issues. In this aspect, a single Cu atom decorated on a carbon nitride (CN) surface (Cu–CN) has gained increasing popularity because of its unique advantages, such as excellent atom utilization and ultrahigh catalytic activity. CN—particularly graphitic CN (g-C3N4)—is a photo- and electrocatalyst and used as an important support material for single Cu atom-based catalysts. These key functions of Cu–CN-based catalysts can improve the catalytic performance and stability in the pCO2R and ECO2R during the application process. In this review, we focus on Cu as a single metal atom decorated on CN for efficient photoelectrochemical CO2 reduction (pECO2R), where ECO2R increases the electrocatalytic active area and promotes electron transfer, while pCO2R enhances the surface redox reaction by efficiently using photogenerated charges and offering integral activity as well as an active interface between Cu and CN. Interactions of single Cu atom-based photo-, electro-, and photoelectrochemical catalysts with g-C3N4 are discussed. Moreover, for a deeper understanding of the history of the development of pCO2R and ECO2R, the basics of CO2 reduction, including pCO2R and ECO2R over g-C3N4, as well as the structural composition, characterization, unique design, and mechanism of a single atom site are reviewed in detail. Finally, some future prospects and key challenges are discussed.

Keywords: carbon dioxide, single copper atom, g-C3N4, reduction


National Oceanic and Atmospheric Administration (NOAA) 2021.

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Publication history
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Publication history

Received: 24 April 2022
Revised: 30 May 2022
Accepted: 07 June 2022
Published: 31 August 2022
Issue date: September 2022


© The Author(s) 2022. Published by Tsinghua University Press.



This work was supported by the "Scientific and Technical Innovation Action Plan" Basic Research Field of Shanghai Science and Technology Committee (No. 19JC1410500), the National Natural Science Foundation of China (No. 91645110), and the Fundamental Research Funds for the Central Universities and Graduate Student Innovation Fund of Donghua University (No. CUSF-DH-D-2021036).

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