Superfast hydrous-molten salt erosion to fabricate large-size self-supported electrodes for industrial-level current OER

Durable, active, and cheap oxygen evolution reaction (OER) electrocatalyst to replace the noble metal-based ones is appealing but challenging in energy storage fields. Here, we devise a one-pot low-temperature hydrous molten salt erosion strategy to vertically root the thin and dense bimetal hydroxide (NiFeOxHy) nanosheet on commercial nickel foam in 1 min. The defect-rich nanosheets are interdigitated together to yield a highly porous array, which offers affluent exposed electroactive centers, decreased charge/mass transfer, and augmented mechanical stability, while a strong Ni-Fe synergy elicits the signal redox reactivity of both metal and nonmetal lattice oxygen. Due to such effects, the typical NiFeOxHy electrode accesses a catalytic current of 10 mA cm−2 at a low overpotential 216 mV for freshwater electrolyte and 232 mV for saline one both with a small Tafel slope of 53 mV dec−1, while stably working for 1000 h at 0.1 A cm−2 in freshwater electrolyte and over 550 h at 1 A cm−2 in saline one. This evidences efficient and stable large-current–density OER performance, particularly a strong Cl− anti-erosion. The large-scale NiFeOxHy electrode materials (81 cm2) with a commensurate performance are fabricated on nickel foam, heralding the enormous prospect for practical usage. This exceedingly procedure-, energy- and time-saving erosion tactic can be generalized to common metal foam substrates and hydrous metal molten salts, accenting a momentous stepping stone for integral construction of self-supported and large-size electrodes towards commercially-met OER application and beyond.