Directionally charging d-orbital electron of Mo2C MXene via in-situ coupled MoSe2 nanosheets for exceptional photocatalytic H2 generation

Abstract

Mo2C MXene as a promising noble-metal-free cocatalyst has attracted considerable attention in the domain of photocatalytic H2 evolution due to its unique 2D layered structure, outstanding metallic conductivity, and Pt-like d-band electronic structure. However, the plentiful −F terminal groups with high electronegativity of Mo2C MXene (referred as Mo2CFx) owing to the residue of F-containing etchants lead to strong interaction between active Mo sites and adsorbed atomic H (Mo-Had bond), thereby decreasing the H2-evolution activity of Mo2CFx. In this work, a directionally charging d-orbital electron strategy of Mo2CFx-MoSe2 heterojunction via increasing the antibonding-orbital occupancy state of Mo to weaken Mo-Had bond in Mo2CFx is presented for the enhanced H2-generation performance. Herein, the ultrathin MoSe2 nanosheets are first vertically grown on the Mo2CFx surface via an in-situ selenization route to form Mo2CFx-MoSe2 heterojunction, and subsequently combined with the TiO2 to prepare the TiO2/Mo2CFx-MoSe2 through an ultrasonic-assisted method. The H2-evolution activity test indicates that the optimal TiO2/Mo2CFx-MoSe2 photocatalyst possesses an exceptional H2-evolution rate (427.66 μmol h−1 g−1), which is 38.98 and 1.94 folds higher than that of the TiO2 and TiO2/Mo2CFx, respectively. The experimental data and density functional theory (DFT) calculations substantiate that the generation of Mo2CFx-MoSe2 heterojunction can weaken the Mo-Had bond by electron transfer from MoSe2 to Mo2CFx for charging d-orbital electrons, accordingly promoting the photocatalytic H2-evolution efficiency of TiO2. This study highlights the optimization of Mo-Had bond by constructing Mo2CFx-based heterojunction to realize high-efficient photocatalytic H2 evolution.