Enhanced photoelectrochemical response of plasmonic Au embedded BiVO₄/Fe₂O₃ heterojunction

The effect of embedding Au nanoparticles (NPs) in a BiVO₄/Fe₂O₃ heterojunction for photoelectrochemical water splitting is studied here for the first time. The present nanostructured heterojunction offers three major advantages over pristine BiVO₄ and Fe₂O₃: (i) the formation of a heterojunction between BiVO₄ and Fe₂O₃ enhances the charge carrier separation and transfer, (ii) the layer of Fe₂O₃ provides protection to BiVO₄ from photocorrosion and, (iii) the Au NPs possessing surface plasmon resonance (SPR) enhance the photoelectrochemical response by transferring energy to metal oxides by hot electron transfer (HET) and plasmon resonant energy transfer (PRET). The present study reveals that the heterojunction ITO/BiVO₄/Fe₂O₃ (with 32% v/v Au solution in both layers) gives the best performance and mitigates the limitations of both pristine Fe₂O₃ and BiVO₄. A thirteen-fold increment in applied bias photon-to-current conversion efficiency (ABPE) was observed at 1.24 V vs. RHE under the condition of 1 Sun illumination. Monochromatic incident photon-to-current conversion efficiency (IPCE) measurements indicated that an Au embedded heterojunction is more effective in harvesting visible light in comparison to a heterojunction without Au NPs.