Abstract

Designing high‐performance electrocatalysts with superior catalytic activity and stability is essential for large‐scale hydrogen production via water electrolysis. Heterostructure nanoarrays are promising candidates, though achieving both high activity and stability simultaneously, especially under high current densities, remains challenging. To this end, we have developed a cascade reaction process that constructs a series of heterostructure nanoarrays with rich heterointerfaces. This process involves treating nickel foam (NF) with molten KSCN and transition metal salts. Initially, NF reacts with KSCN to form Ni9S8 nanoarrays and S2‐ ions, which are subsequently captured by transition metal ions to form sulfides that are directly integrated onto the nanoarrays, resulting in abundant heterointerfaces. Both experimental and theoretical results indicate that these rich heterointerfaces significantly enhance the interfacial interaction between Ni9S8 and RuS2 within the nanoarrays (termed RH‐Ni9S8/RuS2), markedly improving both the intrinsic activity and stability for the hydrogen evolution reaction (HER). Impressively, the RH‐Ni9S8/RuS2 demonstrates exceptional HER performance, achieving a low overpotential of just 180 mV at 1000 mA cm−2 and maintaining stability for up to 500 h under such high‐current‐density conditions. This innovative approach paves the way for the interfacial design and synthesis of high‐performance catalysts for ampere‐level hydrogen production.