Figure 2.

(a) Kinetic versus thermodynamic requirements of various CO₂ reduction reactions. The plotted values are based on the reaction equation given above the graph, made stoichiometric according to the product composition. Reproduced with permission from ref (22). Copyright 2019 Springer Nature. (b) Combined volcano diagrams (lines) for the flat (black) and stepped (red) transition metal surfaces for the reduction of nitrogen with a Heyrovsky-type reaction without (solid lines) and with (dotted lines) H-bond effects. Reproduced with permission from ref (24). Copyright 2012 Royal Society of Chemistry.