2. Fundamentals of Electrochemical CO2Reduction
2.1 Mechanism from
CO2 to CO
The linear molecular structure with high carbon-oxygen bond energy made
CO2 reduction an endothermic reaction in thermodynamics.
Therefore, accomplishing the break of carbon-oxygen bond requires the
external energy. As shown in Figure 1 a (experimental unit), the
electrocatalytic method can directly supply electrons, in favor of the
rapid CO2 reduction. Electrocatalytic
CO2 reduction (ECR) reaction is multi-proton-electron
coupling transfer process, such as two, four, six, eight, etc.
electron pathways (Figure
1b).[35-38] Different electron transfer paths
export different products, even multiple products may be generated in a
reduction system.[35,39,40] Since the main product
of Ni-N-C catalyst is CO via two-electron process, this section mainly
describes the mechanism from CO2 to CO.