Harnessing bifunctional transition metal chalcogenides for high current density sustainable electrolyzer technologies

Abstract

Green hydrogen is a promising cornerstone of the global energy transition due to its potential to enable low-carbon energy systems and support net-zero emission targets. However, its large-scale deployment remains constrained by high production costs, energy inefficiencies, and material limitations in current electrolyzer technologies. A major bottleneck in water electrolysis is the sluggish kinetics of the oxygen evolution reaction (OER), which demands high overpotentials and reduces overall system efficiency. Conventional proton exchange membrane (PEM) electrolyzers rely on scarce and expensive noble metal catalysts and are susceptible to degradation under intermittent renewable energy inputs. Transition metal chalcogenides (TMCs) have emerged as promising alternatives due to their earth abundance, tunable electronic structures, and superior electrochemical properties. Their partially filled d-orbitals enable optimized adsorption of reaction intermediates, thereby lowering kinetic and thermodynamic barriers for both the hydrogen evolution reaction (HER) and OER. Bifunctional TMCs offer the capability to catalyze both half-reactions within a single material system, enhancing efficiency and simplifying electrolyzer design. Their metallic or semi-metallic conductivity, improved charge transfer kinetics, and enhanced resistance to corrosion further position them as viable candidates for sustainable hydrogen production. This review consolidates recent advances in bifunctional TMC electrocatalysts, focusing on synthesis strategies and performance in various electrolyzer configurations. It also highlights key challenges, including catalyst stability, scalability, and integration into commercial systems. By bridging current knowledge gaps, this work aims to provide insights into the rational design of cost-effective, high-performance bifunctional electrocatalysts for next-generation, high current density electrolyzer technologies.