Recent Progress in Bifunctional Electrocatalysts for Overall Water Splitting under Acidic Conditions

Abstract

Water electrolysis is an important energy conversion technology used to produce hydrogen on a mass scale. Until now, special emphasis has been placed on technology development for water electrolysis in acidic electrolytes, owing to the more facilitated hydrogen production under acidic conditions compared to alkaline water electrolysis. Among various catalyst design concepts, bifunctional catalysts capable of driving low overpotentials for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are particularly interesting, owing to the simplicity of cell system design and potential capital reduction for catalyst production. Therefore, it is intriguing to prepare bifunctional catalysts that are compatible with acidic electrolytes. In this Minireview, we introduce the recent progress in bifunctional catalysts for overall water electrolysis under acidic conditions. We briefly describe the merits of water electrolysis in acidic solution and summarize the preparation and performance of the state‐of‐the‐art bifunctional catalysts towards both the acidic HER and OER. Finally, perspectives are provided for the current challenges and opportunities for bifunctional catalysts in acidic water electrolysis.

Recent Development of Oxygen Evolution Electrocatalysts in Acidic Environment

“…We recommend several review articles to readers, which provide the progress review and opinions with other focuses. [225][226][227][228][229] Here, this review article's strategy is to compare the similarities and differences of OER in acidic and alkaline electrolytes, through which a more comprehensive understanding on OER in acid is provided. To guide the future design of better catalysts, we summarize the representatives of the current catalysts toward OER under acidic condition in this section (Figures 13 and 14).…”

Recent Progress in Electrocatalysts for Acidic Water Oxidation

“…[31,32] Despite the aforementioned advantages for PEM electrolyzers, the practical deployment of this technology is impeded largely by the severe degradation of electrocatalysts in acidic electrolytes, especially for OER catalysts that suffer from strongly oxidative environments at high operation voltages. [33][34][35] To address these issues, tremendous efforts have been devoted to boosting the intrinsic activity and enhancing the stability of catalysts in the acidic media. From 1970s, the electrocatalysts in acidic environment are mainly thin films based on metal oxides, such as MoO 2 , WO 2 , ReO 2 , OsO 2 , RuO 2 , and IrO 2 .…”

Design principles of noble metal-free electrocatalysts for hydrogen production in alkaline media: combining theory and experiment

“…Promising and relatively inexpensive transition metal oxides (TMOs) for OER catalysts mostly suffer from serious instability such as decomposition and metal dissolution in acidic and strongly oxidative environments at high operation voltages. 13 Alkaline electrolysis overcomes some of these instability problems and extends the scope of electrocatalysts to earthabundant materials. 14,15 However, the alkaline medium of water splitting causes slow HER kinetics due to the low proton concentration.…”