In Situ Activating Ubiquitous Rust towards Low-Cost, Efficient, Free-Standing, and Recoverable Oxygen Evolution Electrodes.

Developing effective ways to recycle rusted stainless steel and to promote the sluggish oxygen evolution reaction (OER), associated with water splitting and metal-air batteries, is important for a resource-sustainable and environment-friendly society. Herein, we propose a strategy to enable rusted stainless steel plate to be used as an abundant and low-cost OER catalyst, wherein a hydrothermal combined in situ electrochemical oxidation-reduction cycle (EORC) method is developed to mimic and expedite the corrosion process, and thus activate stainless steel into free-standing OER electrodes. Benefiting from the plentiful electrolyte-accessible Fe/(Ni) oxyhydroxides, high conductivity and mechanical stability, this electrode exhibits remarkable OER performances including low overpotential, fast kinetics, and long-term durability. The slight degradation in current after long-term use can be repaired immediately in situ by an EORC.