In the present work, we report significant improvements of the PEC performance of mesoporous BiVO4 photoanodes using a combined strategy of Mo-doping and direct deposition of CoPOM via a simple impregnation protocol without any linkers or binders. The best-performing optimized Mo-BiVO4/CoPOM photoanode exhibits a photocurrent density of 4.32 mA cm -2 at 1.23 V vs. RHE under AM 1.5G (1 sun) irradiation and an applied-bias photoconversion efficiency (ABPE) of ~0.73%, which is an improvement by the factor of 24 and 2.5 compared to pristine BiVO4 (~0.03%) and Mo-BiVO4 (~0.29%), respectively. Furthermore, we disentangle the respective contributions of the Mo-doping and modification with CoPOM to the performance enhancement and show compelling evidence that the beneficial role of CoPOM is related to enhanced kinetics of water oxidation. Finally, we provide several unprecedented insights into the effects of both Mo-doping (e.g., Mo-induced limitation of photovoltage) and CoPOM modification (e.g., compositional changes under operating conditions and significant electrolyte effects), which are of great importance for the further design and development of efficient photoanodes for water splitting.