pH controlled synthesis and photoelectrochemical kinetics of bismuth molybdate (Bi2MoO6) nanoplates as photoanodes for solar-driven water splitting

Metal oxide semiconductors with layered structures such as aurivillius compounds are preferentially used as photoelectrodes in photoelectrochemical water splitting due to their electronic structure, which has contributed to its high stability, excellent photoabsorption in the visible light region, and enhanced catalytic activity. In our present study, bismuth molybdate (Bi2MoO6), a member of the aurivillius family, has been synthesized by adopting solvothermal method in which the pH of the precursor solution has been varied. The powder X-ray diffraction analysis confirms the formation of Bi2MoO6 belonging to the orthorhombic phase. The increase in pH has brought about an increase in the size of the nanoplates, the border length of which are in nano dimensions, which is much evident from the images captured by employing high-resolution scanning electron microscope (HRSEM) and high-resolution transmission electron microscope (HRTEM). The results obtained from UV-visible spectra and Brunauer-Emmett-Teller (BET) analysis disclose the superior light absorbing capability, textural properties, and mesoporous nature of the prepared samples. Bi2MoO6 samples synthesized under different pH conditions were found to display {010} crystal facet, the photoelectrochemical performance of which has been investigated and evaluated. Further, the results reveal that BM-06 sample prepared at pH 6 possesses low onset potential, high photocurrent density, smaller Nyquist arc radius, lower flat band potential, and suitable band edge potentials compared to the rest, which facilitates the material to exhibit an improved PEC water oxidation activity. Herein, the relation between photoelectrochemical water splitting efficiency and the influence of pH on the precursor solution during crystallization of Bi2MoO6 nanoplates have been demonstrated.