Lattice-Matched Iridium on Vanadium Nitride as Efficient Hydrogen Electrocatalyst

Iridium (Ir), with optimal hydrogen binding energy (HBE) and hydroxyl bonding energy (OHBE), is considered a promising platform for achieving bi-directional hydrogen catalysis. However, traditional Ir-based catalysts with multiple crystalline facets exhibit a gap between the apparent activity and theoretical value, especially for the hydrogen oxidation reaction (HOR). Here, a molten co-growth process of Ir and vanadium nitride (Ir-VN) is reported, realizing precise exposure of lattice-matched Ir (111) on VN with optimal HBE and OHBE, for highly active hydrogen catalysis. The Ir-VN catalyst demonstrates exceptional HOR activity with exchange currents 1.8-4.8 times higher than those of noble metal benchmark catalysts, as well as improved durability and CO tolerance. The unique lattice-matching effect promotes the directional electron transfer and induces shortened Ir─Ir bonds via the strongly coupled interface, therefore resulting in enhanced anti-oxidation and anti-CO capability. The Ir-VN catalyst also demonstrates great HER activity and operational durability in a wide pH range, requiring only 21, 12, and 82 mV to reach 10 mA cm^-2 in alkaline, acidic, and neutral conditions, respectively. This work not only deepens the understanding of hydrogen electrocatalysis mechanisms but also inspires the rational design and controllable synthesis of catalysts with active crystal facets for various applications.