Amorphous Zr1-xMnx(OH)4-δ have been investigated toward highly active and robust electrocatalytic hydrogen evolution reaction (HER). Zr0.9Mn0.1(OH)4-δ demonstrates the best HER activity among different metal-substituted (Zr0.9M0.1(OH)4-δ; M = Ni, Co, Cu, and Fe) as well as varied Mn-substituted systems (Zr1-xMnx(OH)4-δ; x = 0.05, 0.15, 0.2, and 0.3). It achieves an overpotential (ƞ10) of 91.3 mV (at j = 10 mA cm-2) in 1 M KOH. Zr0.9Mn0.1(OH)4-δ also exhibits prominent HER activity in stimulated alkaline seawater (ƞ10 = 98.8 mV) and alkaline seawater (ƞ10 = 114 mV), accompanied by prolonged durability in seawater conditions. The multi-step chronopotentiometry exhibits good mass transport and charge-transfer abilities during HER. The improved activity arises from the nanosheet-like structure, having more exposed surface, and oxygen vacancy. Theoretical calculations suggest that Mn-Zr synergy in Zr0.9Mn0.1(OH)4-δ enhances the electronic pπ-dπ coupling, which improves the H* adsorption ability and reduces the energy barrier for HER. The two-electrode cell configured as Zr0.9Mn0.1(OH)4-δ║RuO2 demonstrates a low voltage of 1.59 and 1.7 V (j = 10 mA cm-2) in both media, which is further tested to produce green hydrogen employing solar energy. Thus, the work demonstrates the viability of amorphous Zr0.9Mn0.1(OH)4-δ as a promising candidate for green hydrogen production.
Pradhan et al. (Sun,) studied this question.