Activating Titanium Dioxide as a New Efficient Electrocatalyst: From Theory to Experiment.

Though transition-metal-based materials have emerged as the most promising alternatives to Pt-based electrocatalysts in hydrogen evolution reaction (HER), only a few of them (Fe-, Co-, Ni-, W-, and Mo-based materials) are used as efficient HER electrocatalysts, while others are generally considered as HER-inactive materials with poor activities. Here, a theory-guided experiment is carried out to activate titanium dioxide as a new efficient HER electrocatalyst. First-principles simulations indicate that the hydrogen adsorption free energy could be optimized through tuning the structural and electronic properties of TiO. Then Cu-doped amorphous TiO is successfully prepared based on the theoretical results. The activated TiO expectedly shows excellent HER performance with a low overpotential of 92 mV at 10 mA cm in alkaline media, which is far superior to that of the crystalline TiO (over 400 mV). The origin of HER activity is further investigated in detail. The corrugation of the amorphous surface helps stabilize the adsorbed water molecule, crucial for the water dissociation of the Volmer step. The Cu doping can strengthen the orbital hybridization of H1s and O2p favoring the hydrogen adsorption/desorption and improve the electrical conductivity. Our work highlights the great potential of traditionally inactive materials in HER electrocatalysis and helps deepen our understanding of the catalytic mechanism.