Membraneless unbuffered seawater electrolysis for pure hydrogen production using PtRuTiOx anode and MnOx cathode pairs

Abstract Seawater electrolysis is promising as an in situ H2 production method, allowing immediate overseas transport of the produced H2. Typically, it proceeds under alkaline conditions to ensure the selectivity of the oxygen evolution reaction (OER) over the chloride oxidation reaction (ClOR). In addition, electrolyzers usually require membranes to inhibit the chlorine reduction reaction (ClRR) and maximize the hydrogen evolution reaction (HER) while separating H2 from O2. In this study, membraneless electrolysis of undisturbed, unbuffered seawater (pH 8.2) is proposed to produce high-purity H2. A ternary component catalyst with Pt, Ru, and Ti (PRT) and a minimized Pt level (Pt0.06Ru0.24Ti0.7Ox) drives ClOR at a Faradaic efficiency (FE) of ~100% in saline water at an industrial level of current density (J = 800 mA cm-2) over 500 h. ClRR is also inhibited on MnOx electrodes, leading to ~100% FE of H2 production even in the presence of chlorines (HClO/ClO-). Finally, the PRT anode/MnOx cathode pair drive ClOR and HER at FEs of ~100% at J = 80 mA cm-2 over 100 h in a single-compartment cell containing seawater. Moreover, the OER and ClRR are completely inhibited during seawater electrolysis.