Atomic- and Molecular-Level Modulation of Dispersed Active Sites for Electrocatalytic CO 2 Reduction.

Global climate changes have been impacted by the excessive CO 2 emission, which exacerbates the environmental problems. Electrocatalytic CO 2 reduction (CO 2 RR) offers the solution for utilising CO 2 as feedstocks for value-added products while potentially mitigating the negative effects. Owing to the extreme stability of CO 2 , selectivity and efficiency are crucial factors in the development of CO 2 RR electrocatalysts. Recently, single-atom catalysts have emerged as potential electrocatalysts for CO 2 reduction. They generally comprise of atomically- and molecularly dispersed active sites over conductive supports, which enable atomic-level and molecular-level modulations. In this minireview, catalyst preparations, principle of modulations, and reaction mechanisms are summarised together with related recent advances. The atomic-level modulations are first discussed, followed by the molecular-level modulations. Finally, the current challenges and future opportunities are provided as guidance for further developments regarding the discussed topics.