Mechanically alloyed NiTiO3/transition metal heterostructures: introducing oxygen vacancies for exceptionally enhanced hydrogen evolution reaction activity

Abstract

Hydrogen, a clean and renewable energy carrier, is a promising alternative energy resource to replace fossil fuels. Among various hydrogen production methods, water electrolysis is a sustainable approach to gain pure hydrogen in useful amounts, but its use is still limited by the lack of efficient and low-cost electrocatalysts. Here, a convenient and straightforward mechanical alloying (MA) process is reported that can be used to produce heterostructured catalysts with good performance for the hydrogen evolution reaction (HER). A NiTiO₃/Ni hybrid was reconstructed, which was always considered to be an average HER catalyst, via the ball milling of TiO₂ with Ni powder in a vacuum. The resulting material exhibits an ultra-low overpotential of ∼10 mV at 10 mA cm⁻² (η₁₀) with a Tafel slope of ∼31 mV dec⁻¹, and maintains its stability after running for 200 h in 1 M KOH. In addition, catalysts produced by directly ball milling NiTiO₃ with Ni, Co, or Fe powder also delivered high performance with η₁₀ values of ∼13 mV, 27 mV, and 50 mV, respectively. The enhanced properties are attributed to the introduction of oxygen vacancies into NiTiO₃ and the heterostructures produced via MA, which fully utilize the potential of NiTiO₃ to accelerate water dissociation for the HER in basic media. Because MA is a mature industrial technique, this approach is promising for large-scale applications. The versatile strategy might also benefit and promote the exploration of catalysts for use in other important electrocatalytic fields.