Hexagonal Nickel as a Highly Durable and Active Catalyst for Hydrogen Evolution

The development of highly active and stable earth-abundant electrocatalysts is crucial for the large-scale electrocatalytic hydrogen production. We report herein a crystal-phase heterostructured Ni catalyst with an interior backbone of the face-centered cubic phase covered by a thin surface layer of the hexagonal close packing (hcp) phase. Systematic studies reveal that, upon oxidation, the surface hcp Ni is capable of forming a leaky oxidized layer with abundant Ni0 sites buried underneath. Such underneath Ni0 sites could act synergistically with the leaky surface (hydr)oxide layer from hcp Ni to promote H+ electroreductive formation of H2. The unique surface chemical properties of hcp endow the as-prepared Ni catalyst with high hydrogen evolution activity (112 mV @ 100 mA cm–2) and incredible environment stability even under high current densities and high-concentration alkaline conditions (4–6 M KOH), making it a promising alternative to noble metal catalysts for practical applications in commercial alkaline electrolyzers.