Dual-phase CoP−CoTe2 nanowires as an efficient bifunctional electrocatalyst for bipolar membrane-assisted acid-alkaline water splitting

Abstract

Electrochemical water splitting powered by renewable energy (e.g. solar, wind) has been recognized as a sustainable and environmentally-friendly way to produce “green” hydrogen. Significant efforts were dedicated recently to developing cheap and efficient earth-abundant electrocatalysts to make electrolyzed hydrogen economically competitive. Notwithstanding substantial progress, the operational voltage of water splitting in a single electrolyte system is still high, even highly efficient electrocatalysts are used to catalyze the hydrogen evolution (HER) and oxygen evolution reactions (OER). Taking into account that the HER and the OER are kinetically favorable in electrolytes with different pH values, in this work we demonstrate that overall water splitting can be accomplished in acid-alkaline dual electrolytes with an onset voltage as low as 1.13 V, enabled by a bipolar membrane (BPM) under the “reverse bias” condition with the novel dual-phase cobalt phosphide-cobalt ditelluride (CoP-CoTe2) nanowires being used as efficient and durable bifunctional catalysts. Furthermore, we show that using a BPM under the “forward bias” the voltages needed to reach 10 and 100 mA cm−2 can be reduced to 1.01 and 1.37 V, respectively, due to the assistance of electrochemical neutralization resulting from the crossover of electrolytes. The bipolar membrane water electrolysis (BPMWE) can be sustained for at least 100 h without notable degradation.