Efficient Bipolar Membrane Water Electrolysis Enabled By Dual-Phase CoP-CoTe2 Nanowires As Bifunctional Electrocatalyst

Abstract

Water splitting offers an environmentally friendly way for H2 production, especially if the electricity comes from renewable sources such as solar and wind. Significant effort has recently been made to developing cheap and efficient earth-abundant electrocatalysts to make electrolyzed hydrogen economically competitive. Although the substantial progress, the operational voltage of water splitting in a single electrolyte system is still high. Given that the hydrogen evolution reaction (HER) is kinetically favorable in acidic conditions and the oxygen evolution reaction (OER) in alkaline conditions, it would be preferable to realize these half reactions simultaneously in different electrolytes in a single electrolyzer. Moreover, such cell design allows the using of low-cost and earth-abundant catalysts for both HER and OER.In this work we demonstrate the development of a dual-phase cobalt phosphide-cobalt ditelluride (CoP-CoTe2) nanowires, which can be used as efficient bifunctional electrocatalysts for both HER and OER using acid-alkaline dual electrolytes in a two-compartment cell separated by a bipolar membrane (BPM). Using the BPM under "reverse bias" configuration, the bipolar membrane overall water splitting can be accomplished with an onset voltage as low as 1.13 V and a voltage of 1.72 V is needed to deliver 10 mA cm-2. However, water electrolysis can be accomplished at significantly lower external biases, e.g. 1.01 V at 10 mA cm-2, when a "forward bias" conditions was used due to the assistance of electrochemical neutralization. Moreover, this electrolyzer can sustain water splitting for at least 100 h. The bipolar membrane water electrolysis, particularly with the "forward bias" configuration, shows great promise as an alternative to the current technologies.