Fig. 9
From: Hydrogen production from water electrolysis: role of catalysts
(Figure reprinted with permission from Ref. [57])
a OER mechanisms in acidic (blue line) and alkaline (red line) electrolytes (Figure reprinted with permission from Ref. [5]). b Free energy diagram at U = 0 and U = 1.23 V for OER on the ideal catalyst (Figure reprinted with permission from Ref. [55]). c Relationship between the adsorption energies of *OOH and *OH on a series of oxide OER catalysts (Figure reprinted with permission from Ref. [56]). d Volcano-shaped relationship between OER activities on metal oxide surfaces vs. enthalpy for the transition metal oxides in acidic (black square) and basic solution (white square)