Heterostructured Electrocatalysts for Hydrogen Evolution Reaction Under Alkaline Conditions

Abstract

The hydrogen evolution reaction (HER) is a half-cell reaction in water electrolysis for producing hydrogen gas. In industrial water electrolysis, the HER is often conducted in alkaline media to achieve higher stability of the electrode materials. However, the kinetics of the HER in alkaline medium is slow relative to that in acid because of the low concentration of protons in the former. Under the latter conditions, the entire HER process will require additional effort to obtain protons by water dissociation near or on the catalyst surface. Heterostructured catalysts, with fascinating synergistic effects derived from their heterogeneous interfaces, can provide multiple functional sites for the overall reaction process. At present, the activity of the most active known heterostructured catalysts surpasses (platinum-based heterostructures) or approaches (noble-metal-free heterostructures) that of the commercial Pt/C catalyst under alkaline conditions, demonstrating an infusive potential to break through the bottlenecks. This review summarizes the most representative and recent heterostructured HER catalysts for alkaline medium. The basics and principles of the HER under alkaline conditions are first introduced, followed by a discussion of the latest advances in heterostructured catalysts with/without noble-metal-based heterostructures. Special focus is placed on approaches for enhancing the reaction rate by accelerating the Volmer step. This review aims to provide an overview of the current developments in alkaline HER catalysts, as well as the design principles for the future development of heterostructured nano- or micro-sized electrocatalysts.

Construction and Application of Interfacial Inorganic Nanostructures

“…The HER is a two‐electron transfer process, which undergoes Volmer‐Heyrovsky or Volmer‐Tafel routes. [ 92 ] It is slightly different for the reaction pathways of HER in acidic and alkaline conditions. The rate of the entire reaction highly depends on the free energy for hydrogen adsorption (Δ G H ).…”

Enhanced hydrogen evolution reaction on highly stable titania‐supported PdO and Eu2O3nanocomposites in a strong alkaline solution

“…Such features rendered PtCuNi/CNF@CF as an ideal binder‐free electrocatalyst for the HER. Others synthesized new ternary catalysts and reported them as highly active materials for the HER and water splitting …”

Synergism of Interface and Electronic Effects: Bifunctional N‐Doped Ni3S2/N‐Doped MoS2 Hetero‐Nanowires for Efficient Electrocatalytic Overall Water Splitting

“…[19][20][21][22][23][24][25][26][27][28][29][30][31] The origin for the enhancementi n electrocatalytic performance of HER-OERb ifunctional heterogeneous catalysts is the well-recognized interface effect, which can greatly promote the reactionk inetics on catalytically active sites. [32][33][34][35][36][37][38][39][40] Among various structures, 1D hetero-nanowires have been demonstrated to be superior for gas-involving electrocatalysis;t his is mainly attributed to their abundant,w ell-exposed active sites;e fficient charge transfer;a nd unique surface properties for gas evolution and release. [41][42][43][44] Apart from structure engineering, regulating the composition of electrocatalysts by heteroatom doping is another alternative strategy to boost the catalytic activity.…”