Preparation of CoMoP/BiVO4 Composite Photoanodes and Investigation of Their Photoelectrochemical Properties

Herein, a cobalt–molybdenum bimetallic oxide precursor was synthesized via a hydrothermal route, followed by a phosphidation strategy in a tube furnace to produce a CoMoP cocatalyst. Subsequently, a CoMoP/BiVO4 composite photoanode was successfully constructed by loading the CoMoP cocatalyst onto the surface of an electrodeposited BiVO4 film using a drop-casting method. A suite of analytical tools such as TEM, XRD, and XPS was utilized to comprehensively examine the material morphology and crystalline features, verifying that CoMoP was effectively anchored on the BiVO4 surface with intimate interfacial contact. Photoelectrochemical (PEC) performance testing indicated that the composite photoanode achieved optimal performance with a 200 µL loading of the CoMoP dispersion (2 mg/mL). Under front-side illumination, the photocurrent density of the CoMoP/BiVO4 composite photoelectrode reached a photocurrent density of 2.8 mA/cm2 at 1.23 V (vs. RHE), which is approximately 3.1 times higher than that of unmodified BiVO4 (0.9 mA/cm2). Under back-side illumination, the composite photoanode generated 3.5 mA/cm2, representing a 2.3-fold improvement over the 1.5 mA/cm2 recorded for bare BiVO4. The bandgap energy of BiVO4 was determined to be approximately 2.44 eV based on UV–vis absorption spectra and the corresponding Tauc plot. Owing to its metallic nature, CoMoP exhibits strong broadband absorption in the visible-light region and does not display an intrinsic semiconductor bandgap behavior. Combined with photoluminescence (PL) spectroscopy and PEC results, it was demonstrated that the CoMoP loading effectively promoted interfacial charge separation and transport while accelerating water oxidation kinetics. These results demonstrate that the CoMoP/BiVO4 system serves as an advanced semiconductor material with excellent performance for photoelectrocatalytic water splitting.