Tunable Photocatalytic HER Activity of Single-Layered TiO<sub>2</sub> Nanosheets with Transition-Metal Doping and Biaxial Strain

The hydrogen evolution reaction (HER) and electronic properties of single-layered TiO<sub>2</sub> nanosheets effectively modulated by transition-metal doping and biaxial strain were investigated in this work. Surprisingly, the hydrogen adsorption free energy of Cr-doped LNS-TiO<sub>2</sub> nanosheets was reduced to almost 0 eV, which is comparable to the well-known highly efficient catalyst of Pt metal. The tunable hydrogen adsorption ability was correlated with the O-2p<sub><i>z</i></sub> band center level. Moreover, by upshifting the p<sub><i>z</i></sub> band center level, both the tensile and compressive strains could decrease the hydrogen adsorption free energy of V-doped LNS-TiO<sub>2</sub> nanosheets, even close to 0 eV with 7% tensile strain. These insights open a new avenue into realizing high HER activity in oxide nanosheets.