Accelerated photoelectrochemical oxygen evolution over a BaTaO₂N photoanode modified with cobalt-phosphate-loaded TiO₂ nanoparticles

Because the oxygen evolution reaction (OER) involves a complicated four-electron process, reducing the overpotential for the OER by loading cocatalysts at as high a concentration as possible is critical for achieving efficient photoelectrochemical (PEC) water oxidation. However, such surface modifications should also be designed to not interfere with the bandgap photoexcitation of the light-absorbing materials. In the present study, cobalt-phosphate-loaded TiO₂ (CoPi/TiO₂) nanoparticles were used to modify a particulate BaTaO₂N (BTON) photoanode, resulting in an improvement in the photoanode PEC OER performance. The TiO₂ nanoparticles functioned as a transparent and conductive support with a high specific surface area to immobilize CoPi on the photoanode surface. Electrochemical measurements revealed that the CoPi/TiO₂ modification led to improved reaction kinetics and that the electrochemically active surface area of the CoPi cocatalysts deposited on the electrode surface substantially increased by a factor of 7.45 as a result of the TiO₂ modification. The CoPi/TiO₂ modification increased the number of active sites on the surface of the particulate BTON photoanode and minimized the harmful influence of light shielding, thereby accelerating the OER kinetics.