Oxygen vacancy engineered electron structure of porous CexCo3−xO4 nanorods for wide spectrum photocatalytic hydrogen evolution

Abstract

Development of high-performance semiconductors for photocatalytic hydrogen evolution is a promising solution to solve the current energy crisis. In this work, a porous and oxygen vacancy-enriched CexCo3−xO4-Vo nanorods (CexCo3−xO4-Vo NRs) with adjust electron structure were fabricated by Ce-doping for wide spectrum photocatalytic hydrogen evolution. Because Ce doping regulates the Co3+/Co2+ atomic ratio of Co3O4 nanorods (Co3O4 NRs), resulting in a reduction of oxygen vacancy formation energy and confirmed by electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy measurements (XPS) studies. The formation of oxygen vacancy leads to a modification in the positions of conduction band and valence band positions of CexCo3−xO4-Vo NRs. The ultraviolet photoelectron spectroscopy (UPS) spectra results indicate that the generation of oxygen vacancies leads to a more negative Fermi level in CexCo3−xO4-Vo NRs. This result directly results in an enhanced capacity for H+ reduction of CexCo3−xO4-Vo NRs. Density functional theory (DFT) calculations demonstrate that Ce0.15Co2.85O4-Vo NRs have faster electron transfer rates. In addition, the porous rod-like structure endows it abundant electron diffusion pathways, facilitates electrolyte infiltration, and establishes an ideal electrolyte/catalyst contact interface. Among them, Ce0.15Co2.85O4-Vo NRs have the best photocatalytic hydrogen evolution activity (3912.8 μmol g−1), which were 2.2 times more than that of Co3O4 NRs, and an excellent stability also obtained. This work provides a new idea for elements doping Co3O4 NRs to in situ-induced oxygen vacancies for enhanced photocatalytic hydrogen evolution.