New TiO 2 -Based Oxide for Catalyzing Alkaline Hydrogen Evolution Reaction with Noble Metal-Like Performance.

The development of cost-effective electrocatalysts with high activity and sufficient stability for hydrogen evolution reaction (HER) is crucial for the widespread application of water electrolysis for sustainable H 2 production. Transition metal oxides are desirable alternatives to replace benchmark Pt-based HER electrocatalysts because of their cost effectiveness, facile synthesis, versatile compositions, and easy electronic structure tuning. However, most available transition metal oxides show poor performance for HER catalysis. Here, it is reported that the anatase TiO 2 can be efficiently developed into a superior HER electrocatalyst with comparable activity to Pt-based electrocatalysts in alkaline solution through simultaneous morphology control, proper lattice doping, and surface active sites engineering. Specifically, the obtained cobalt-doped TiO 2 nanorod arrays (Co-TiO 2 @Ti(H 2 )) show a low overpotential of only 78 mV at 10 mA cm -2 , a small Tafel plot of 67.8 mV dec -1 , and excellent stability even at an ultralarge current density of ≈480 mA cm -2 in 1.0 m KOH solution. Theoretical calculations demonstrate that the introduction of Co with rich oxygen vacancies can efficiently lower the energy barrier for water adsorption/dissociation and H intermediate desorption. This work uncovers the potential of the low-cost transition metal oxides as alternative HER electrocatalysts in alkaline water electrolysis.