Electrolysis of natural waters contaminated with transition-metal ions: identification of a metastable FePb-based oxygen-evolution catalyst operating in weakly acidic solutions

The possibility of efficient water electrooxidation sustained by continuous (re)generation of catalysts derived from the oxidative electrodeposition of transition-metal contaminants is examined herein for three natural water samples from Australia and China. The metal composition of the solutions has been determined by inductively coupled plasma optical emission spectrometry, and a range of strategies to produce water-splitting catalysts by means of in situ electrodeposition have been applied. The performance of the resulting electrocatalysts is below the state-of-the-art level owing to large amounts of impurities in the solutions and non-optimal concentrations of naturally available catalyst precursors. Nevertheless, these studies have identified the FePb-based system as a rare example of an electrocatalyst for water oxidation that forms in situ and maintains reasonable activity (≥4.5 mA cm⁻² at an overpotential of 0.8 V) in weakly acidic solutions (pH 2.9).