Facile synthesis of bismuth vanadate/bismuth oxide heterojunction for enhancing visible light-responsive photoelectrochemical performance

BiVO4 is a well-known photocatalyst for water oxidation due to small band gap and suitable band positions, but short diffusion length is necessary to solve for practical applications. This study adopts common alkaline etching process for fabricating BiVO4 and BiOx composite as photocatalyst for water oxidation for the first time. The BiVO4/BiOx heterojunction is fabricated on conducting glasses using hydrothermal synthesis and NaOH etching process for establishing heterojunction. Different NaOH concentrations are used for fabricating BiVO4/BiOx electrodes with different BiOx amounts. Due to adequate amount of BiOx for achieving effective charge transfer and suitable amount of continuous aggregations on the surface for reducing charge recombination at nanoparticle boundaries, the BiVO4/BiOx electrode prepared using 0.15 M NaOH for etching shows the highest photocurrent density of 0.48 mA/cm2 at 1.23 V versus reversible hydrogen electrode under air mass 1.5 global illumination. The BiVO4 electrode only shows the photocurrent density of 0.06 mA/cm2 measured at the same conditions. Long-term stability of the BiVO4/BiOx electrode is further improved by ten-fold after depositing NiOOH co-catalyst on the surface for reducing charge recombination. The result indicates the significance for the bismuth oxide amount in the BiVO4/BiOx composite on influencing the photoelectrochemical catalytic ability toward water oxidation.