Selective Seawater Splitting Using Pyrochlore Electrocatalyst

Seawater electrolysis is emerging as one of the most promising technologies for hydrogen and oxygen generation for spatially constrained offshore and mobile-maritime applications. Herein, we show that lead ruthenate pyrochlore (Pb2Ru2O7-x) electrocatalyst displays higher OER (oxygen evolution reaction) activity and selectivity over parasitic ACSFR (active chlorine species formation reaction) in comparison to other reported electrocatalysts during simulated seawater electrolysis. The higher OER selectivity and activity of Pb2Ru2O7-x as compared to benchmark RuO2 is ascribed to the presence of a greater concentration of surface Ru(V) and oxygen vacancies. Simulated seawater electrolysis using Pb2Ru2O7-x yields higher OER activity (60-fold) and selectivity at pH = 13 (∼99%) than at pH = 7 (∼68%) due to the unfavorable thermodynamics and kinetics of ACSFR at high pH. A current density of 275 mA/cm2 is obtained at a cell voltage of 1.80 V at pH = 13 in an electrolyzer, with 10 mV voltage loss at 200 mA/cm2 over 5 h of operation.