Hierarchical growth of a novel Mn-Bi coupled BiVO₄ arrays for enhanced photoelectrochemical water splitting

Oxygen evolving catalyst (OEC) is a critical determinant for the efficiency of photoelectrochemical (PEC) water splitting. Here we report an approach to depositing a novel manganese borate (Mn-Bi) OER catalyst on BiVO₄ nanocone photoanode by photodeposition in sodium borate buffer solution containing Mn(Ⅱ) ions. Due to the spontaneous photo-electric-field-enhancement effect at the vertically oriented BiVO₄ nanocone structure, spherical Mn-Bi nanoparticle was selectively photodeposited at the apex of BiVO₄ nanocone. Significant improvement of photocurrent was observed for the obtained hierarchical Mn-Bi/BiVO₄ photoanode which could be ascribed to enhanced hole injection efficiency, especially in low bias region. It was observed that the injection efficiency of Mn-Bi/BiVO₄ is 98% which gave a photocurrent of 0.94 mA/cm² at 1.5 V vs. RHE.