Modulation of electronic and optical properties of g-CN/XTe2(X=W, Mo) heterojunctions by biaxial strain

The electronic and optical properties under biaxial strains, as well as the Gibbs free energy profiles for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of the g-C 3 N 4 /WTe 2 and g-C 3 N 4 /MoTe 2 (g-CN/XTe 2 , X = W, Mo) heterojunctions were studied by first-principles based on density functional theory (DFT). The g-CN/WTe 2 and g-CN/MoTe 2 heterojunctions exhibit type-II band alignment, and are direct bandgap semiconducting with bandgap of 1.272 eV and 1.481 eV, respectively. Compared to intrinsic g-CN, the g-CN/XTe 2 heterojunctions show enhanced light absorption in the ultraviolet and visible regions. The power conversion efficiency (PCE) of the g-CN/WTe 2 and the g-CN/MoTe 2 heterojunctions are 17.89 % and 22.37 %, respectively. Under the biaxial strain, the bandgap, band alignment, light absorption properties and PCE of the g-CN/XTe 2 (X = W, Mo) heterojunctions can be modulated. Especially, the PCE of the g-CN/WTe 2 heterojunction increases up to 22.52 % under 2 % biaxial strain. In addition, under 4H coverage, the over-potentials of HER in g-CN/WTe 2 and g-CN/MoTe 2 are 1.149 V and 1.148 V, and the over-potentials of OER are 2.341 V and 2.438 V, respectively. These results indicate that g-CN/XTe 2 heterojunctions hold promise for applications in solar cell devices and electrocatalytic hydrogen production . • The PCE of the g-CN/MoTe 2 heterojunction reach 22.37 %. • For the g-CN/WTe 2 heterojunction, the PCE increases form 17.89 %–22.52 % at 2 % strain. • Under biaxial strains, absorption spectra of g-CN/XTe 2 heterojunctions are redshifted. • The g-CN/XTe 2 heterojunctions achieve low over-potentials of HER under 4 H coverage.