The sluggish kinetics of the hydrogen evolution reaction in base has resulted in large activity gap between acidic and alkaline electrolytes. Here, we present an intermetallic IrMo electrocatalyst supported on carbon nanotubes that exhibits a specific activity of 0.95 mA cm⁻² at the overpotential of 15 mV, which is 14.4 and 9.5 times of those for Ir/C and Pt/C, respectively. More importantly, its activities in base are fairly close to that in acidic electrolyte and the activity gap between acidic and alkaline media is only one fourth of that for Ir/C. DFT calculations reveal that the stably-adsorbed OH spectator at Mo site of IrMo can stabilize the water dissociation product, resulting in a thermodynamically favorable water dissociation process. Beyond offering an advanced electrocatalyst, this work provides a guidance to rationally design the desirable HER electrocatalysts for alkaline water splitting by the stably-adsorbed OH spectator.

Fuel cells are considered renewable and clean energy sources to replace the dwindling fossil fuel resources. However, the sluggish reaction kinetics of the anodic fuel oxidation and cathodic oxygen reduction reactions hinder the wide commercialization of fuel cells. The Pt/C material is still the most efficient electrocatalyst; however, its high price and poor stability severely impede its large-scale application. Recently, transition metal nitrides (TMNs) have been regarded as promising electrocatalyst materials owing to their unique physical, chemical, and electronic properties, e.g., thermal stability, metallic conductivity, great hardness, and corrosion resistance. Herein, the advances pertaining to TMN-based catalyst materials for fuel cells are reviewed, ranging from their structures, properties, and synthesis to their applications. TMNs can act as catalysts or supports in electrocatalytic processes. Briefly, as catalysts, TMNs are grouped into free-standing TMNs (including binary and ternary TMNs) and TMN/carbon composites. Moreover, as supports, TMNs can be categorized as pure TMNs supports and hybrid supports to anchor noble metals. Finally, the challenges and perspectives of TMN-based catalyst materials for high-performance fuel cell systems are discussed.