Coupling hole-transporting polyaniline layer with a cobalt phthalocyanine cocatalyst to boost photoelectrochemical water oxidation of bismuth vanadate photoanodes

Though bismuth vanadate (BiVO4) exhibits a promising potential as a semiconductor photoanode toward photoelectrochemical (PEC) water oxidation, its PEC performance is still limited by the poor charge carrier transport and sluggish oxygen evolution kinetics. Herein, the polyaniline (PANI) and cobalt coordinated-phthalocyanines (CoTcPc) were introduced onto the BiVO4 semiconductor substrate, constructing the integrated CoTcPc/nPANI/BiVO4 (n = 30, 60 and 90, n represents the deposition time for PANI with the unit of s) composite photoanodes. It is demonstrated that the PEC water oxidation activity of BiVO4 is significantly boosted by the incorporation of PANI and CoTcPc, stemming from the improved electron/hole transfer, enhanced charge separation efficiency, and accelerated carrier mobility and water oxidation kinetics. CoTcPc/60PANI/BiVO4 composite photoanode with the optimized compositions exhibits an enhanced photocurrent density of 4.03 mA/cm2 at 1.23 V vs. RHE under illumination, ranking among the best records reported recently. Furthermore, the roles of electrodeposition time to generate PANI are also distinguished through experimental studies. These results reveal the crucial role of engineering the hole transfer layer to optimize the semiconductor photoanodes toward efficient PEC water oxidation.