Main content area

The Importance of the Interfacial Contact: Is Reduced Graphene Oxide Always an Enhancer in Photo(Electro)Catalytic Water Oxidation?

Xie, Zhirun, Tan, Hui Ling, Wen, Xiaoming, Suzuki, Yoshitaka, Iwase, Akihide, Kudo, Akihiko, Amal, Rose, Scott, Jason, Ng, Yun Hau
ACS applied materials & interfaces 2019 v.11 no.26 pp. 23125-23134
bismuth, composite materials, electric current, graphene, graphene oxide, hydrophobicity, oxidation, oxygen production, photocatalysis, semiconductors, silver, silver chloride, wettability
Optimizing interfacial contact between graphene and a semiconductor has often been proposed as essential for improving their charge interactions. Herein, we fabricated bismuth vanadate-reduced graphene oxide (BiVO₄/rGO) composites with tailored interfacial contact extents and revealed their disparate behavior in photoelectrochemical (PEC) and powder suspension (PS) water oxidation systems. BiVO₄/rGO with a high rGO coverage on the BiVO₄ surface (BiVO₄/rGO HC) exhibited an 8-fold enhancement in the PEC photocurrent density with respect to neat BiVO₄ at 0 V versus Ag/AgCl, while BiVO₄/rGO with a low rGO coverage (BiVO₄/rGO LC) gave a lesser 3-fold enhancement. In contrast, BiVO₄/rGO HC delivered a detrimental effect, while BiVO₄/rGO LC exhibited an enhanced performance for oxygen evolution in the PS system. The phenomenon is attributed to changes in the hydrophobicity of the BiVO₄/rGO composite in conjunction with the interfacial contact configuration. A better BiVO₄/rGO interfacial contact was found to improve the charge separation efficiency and charge transfer ability of the composite material, explaining the superior PEC performance of BiVO₄/rGO HC. Additionally, optimization of the interfacial contact extent was revealed to further improve the energetics of the composite material, as evidenced by a Fermi level shift to a more negative potential. However, the high hydrophobicity of BiVO₄/rGO HC arising from the higher rGO reduction extent triggered poor water miscibility, reducing the surface wettability and therefore hampering the photocatalytic O₂ evolution activity of the sample. The study underlines water miscibility as a governing issue in the PS system.