Mechanically Alloyed NiTiO3/Transition Metal Heterostructures: Introducing Oxygen Vacancies for Exceptionally Enhanced Hydrogen Evolution Reaction Activity

Hydrogen—a clean and renewable energy carrier, is a promising alternative energy resource to fossil fuels. Among various hydrogen production methods, water electrolysis is a sustainable approach to gain pure hydrogen in amount but still limited by the less of efficient and low-cost electrocatalysts. Here, we report that a convenient and straightforward mechanical alloying (MA) process can be used to produce top-performance heterostructured catalysts for hydrogen evolution reaction (HER). We reconstruct NiTiO3/Ni hybrid, which was ever considered as an average HER catalyst, via ball milling TiO2 with Ni powder in 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 stable after running for 200 hours in 1 M KOH. In addition, catalysts via directly ball milling NiTiO3 with Ni, Co, or Fe powder also deliver high performance with η10 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 excite the potential of NiTiO3 to accelerate water dissociation for HER in basic media. Since MA is a mature industrial technique, this approach is promising for large-scale applications. The versatile strategy might also benefit and promote the catalyst exploration for other important electrocatalytic fields.