Enriched Photoelectrochemical Performance of Phosphate Doped BiVO₄Photoelectrode by Coupling FeOOH and rGO

Bismuth vanadate is a promising photoanode with a set of intrinsic limitations for water oxidation and photoelectrochemical degradation of organic pollution. FeOOH/P:BiVO 4 /rGO composite with a considerably small charge-transfer resistance was successfully developed by doping the BiVO 4 lattice with phosphate (P:BiVO 4 ), photo-depositing FeOOH nanoparticles on P:BiVO 4 nanoparticles, and grafting reduced graphene oxide (rGO) onto the surface of P:BiVO 4 , in that order. This composite photoelectrode significantly improves photoelectrochemical performance originating from its effective suppression on electron-hole recombination and charge transfer at the semiconductor/electrolyte interface. The photoelectrocatalysts were systematically characterized by FTIR, XPS, SEM, TEM, UV-vis and XRD. The characterization results show that FeOOH/P:BiVO 4 /rGO consisted of spherical agglomerates comprising a large number of P:BiVO 4 nanoparticles with an average size of approximately 10 nm. FeOOH nanoparticles were successfully loaded onto the surface of P:BiVO 4 nanoparticles, and rGO layers with a thickness of approximately 4 nm were coated onto the P:BiVO 4 particles. The enhanced photoelectrochemical properties were observed using linear sweep voltammetry. The mechanism underlying the observed photoelectrocatalytic activity enhancement was determined using Mott-Schottky analysis and electrochemical impedance spectroscopy. The photocurrent density of FeOOH/P:BiVO 4 /rGO in a Na 2 SO 4 solution with 2,4-dichlorophenol (2,4-DCP) at 0.6 V Ag/AgCl is approximately 100 times higher than that of P:BiVO 4 ; the onset potentials of FeOOH/P:BiVO 4 /rGO (0.008 V Ag/AgCl ) is 5 times lower than that of P:BiVO 4 (0.043 V Ag/AgCl ). It is suggested that FeOOH/P:BiVO 4 /rGO obtains the highest photoelectrocatalytic performance for 2,4-DCP degradation. The proposed mechanism is that the synergistic effect between FeOOH and rGO can alleviate two main limitations of P:BiVO 4 : suppression on the bulk recombination and interfacial recombination formed at the P:BiVO 4 -FeOOH junction and effective charge transfer at the semiconductor/electrolyte interface.