Sustainable oxygen-evolving electrode via in situ regenerative deposition of hexahydroxyiridate (IV)

Water splitting is regarded as the essential reaction for converting intermittent energy into hydrogen fuel. Sustainability of the oxygen-evolving electrode determines efficient and economic hydrogen production. Using Ir derivatives in an electrolyte, we report an in situ catalyst regenerative deposition which substantially prolongs the lifetime of an IrOx oxygen-evolving electrode. Taking pH-dependent and reversible conversion between hexahydroxyiridate (IV) ([Ir(OH)6]2−) and IrOx, an IrOx-regenerative deposition concurrent with oxygen evolution reaction (OER) is demonstrated. Time of electrolysis and overpotential of the IrOx electrode are studied as a function of pH of the Ir species contained in alkaline electrolyte. The regenerative deposition process is verified by ex situ cyclic voltammetry. The transmission electron microscope, zeta potential, and diffusivity studies suggest the prominent role of hydrous [Ir(OH)6]2−-adsorbed IrOx nanoparticles in determining the efficiency of catalyst redeposition. Per the behaviour, a sustainable oxygen-evolving electrode succeeds in acidic electrolyte to exhibit an approximately 1390-fold enhancement in durability compared with a system without Ir species. Under the presence of the Ir species, lower catalyst dissolution rate is observed. The design offers an approach for efficient utilization of IrOx catalysts towards practical hydrogen production.

https://www.sciencedirect.com/science/article/pii/S0013468621005818#fig0001