Boosting catalytic performance of hierarchical Co/Co0.85Se microspheres via Mott-Schottky effect toward triiodide reduction and alkaline hydrogen evolution

Interface engineered composites composing of metal and transition metal selenides have been deemed as promising substitutes as noble Pt in the fields of the energy conversion. Herein, the well-defined hierarchical Co/Co0.85Se microsphere with Mott-Schottky (M-S) effect was synthesized by the facile solvothermal method (Co/Co0.85Se-3). Interestingly, the as-obtained 3D Co0.85Se microsphere was assembled by 2D porous nanosheets. The characteristics including M-S heterojunction and hierarchical structure endows Co/Co0.85Se microsphere with high specific surface area, good conductivity, and synergistic effect between metal Co and Co0.85Se. More concretely, the optimized Co/Co0.85Se exhibits outstanding catalytic activity toward triiodide reduction reaction (IRR). When employed as the counter electrode (CE) catalyst for dye-sensitized solar cell (DSSC), a photoelectric conversion efficiency (PCE) of 8.31 % is achieved, which is 3.36 % higher than that of Pt-control device (8.04 %). Moreover, Co/Co0.85Se-3 displays remarkable catalytic activity for hydrogen evolution reaction (HER) with a low overpotential of 107 mV at the current density of 10 mA cm−2 under alkaline condition (1.0 M KOH), accompanying with Tafel slope of 140 mV dec−1. Our discovery provides an effective approach to develop the cost-effective advanced catalysts to promote the application of DSSC and HER.