Figure 1. (a) Schematic illustration of experimental H-type
electrolytic cell for electrochemical CO2 reduction; (b)
Thermodynamic equilibrium potential diagram of some value-added
compounds from ECR in the aqueous electrolyte (pH = 7); (c) Proposed
reaction pathway of CO2 reduction to CO production.
As displayed in Figure 1c, the
formation process (3) of COOH* can be divided into two concerted
proton–electron transfer (CPET) steps: (1) and (2). Previous studies
have demonstrated that rate-determining steps (RDS) may be (3) or (4),
depending on the COOH* binding
energy and the CO* desorption
energy.[41,42] Therefore, the accurate regulation
of the adsorption strength of key intermediates is fairly essential to
exploit the reasonable
electrocatalyst for reducing
CO2 to CO.[43,44] Notably, except
the ECR process, hydrogen adsorption on the electrocatalyst surface
needs to be considered, because that HER is the main competitor of ECR.
Stronger H* binding ability is required to rise HER overpotential, which
will help promote the occurrence of ECR.[45,46]