Enhanced photoelectrochemical performance of Z-scheme g-C3N4/BiVO4 photocatalyst

Abstract

BiVO 4 is a considerably promising semiconductor for photoelectrochemical water splitting due to its stability, low cost and moderate band gap. In this research, g-C 3 N 4 was proposed in Z-scheme configuration which boosted the performance of BiVO 4 up to four times. The experimental observations were counterchecked with Density Functional Theory (DFT) simulations. A TiO 2 /BiVO 4 heterojunction was developed and its performance was compared with that of g-C 3 N 4 /BiVO 4 . The photocurrent for g-C 3 N 4 /BiVO 4 was 0.42 mAcm −2 at 1.23 V vs. RHE which was the highest among g-C 3 N 4 based Z-scheme heterojunction devices. Lower charge transfer resistance, higher light absorption and more oxygen vacancy sites were observed for the g-C 3 N 4 based heterojunction. The simulated results attested that g-C 3 N 4 and BiVO 4 formed a van der Waals type heterojunction, where an internal electric field facilitated the separation of electron/hole pair at g-C 3 N 4 /BiVO 4 interface which further restrained the carrier recombination. Both the va lence and conduction band edge positions of g-C 3 N 4 and BiVO 4 changed with the Fermi energy level. The resulted heterojunction had small effective masses of electrons (0.01 m e ) and holes (0.10 m e ) with ideal band edge positions where both CBM and VBM were well above and below the redox potential of water.