The electrochemical reduction of carbon dioxide (CO2) to value-added products is a remarkable approach for mitigating CO2 emissions caused by the excessive consumption of fossil fuels. However, achieving the electrocatalytic reduction of CO2 still faces some bottlenecks, including the large overpotential, undesirable selectivity, and slow electron transfer kinetics. Various electrocatalysts including metals, metals oxides, alloys, and single-atom catalysts have been widely researched to suppress HER performance, reduce overpotential and enhance the selectivity of CO2RR over the last few decades. Among them, single-atom catalysts (SACs) have attracted a great deal of interest because of their advantages over traditional electrocatalysts such as maximized atomic utilization, tunable coordination environments and unique electronic structures. Herein, we discuss the mechanisms involved in the electroreduction of CO2 to carbon monoxide (CO) and the fundamental concepts related to electrocatalysis. Then, we present an overview of recent advances in the design of high-performance noble and non-noble singleatom catalysts for the CO2 reduction reaction.

Abstract
1. Introduction
2. Fundamentals of the CO2RR on SACs
    2.1. Mechanism of CO2 to CO conversion
    2.2. Parameters
3. Electrocatalytic Performance of SACs forCO2RR
    3.1. Noble-metal-based SACs
    3.2. Non-noble metal SACs
4. Conclusion
Acknowledgement
References

• Joonhee Ma(Department of Materials Science and Engineering, Korea University)
• Jin Hyuk Cho(Department of Materials Science and Engineering, Korea University)
• Kangwon Lee(Department of Applied Bioengineering, Graduate School of Convergence Science and Technology, Seoul National University, Research Institute for Convergence Science, Seoul National University)
• Young Kim(Department of Materials Science and Engineering, Korea University) Corresponding author