Electrodeposited single-crystalline PbCrO4 microrods for photoelectrochemical water oxidation: enhancement of minority carrier diffusion

Abstract

In this study, we report noticeable photoelectrochemical water oxidation on single-crystalline PbCrO₄ microrods. Microrods are directly formed on fluorine-doped tin oxide via electrodeposition based on the electrochemical oxidation of Cr³⁺ to Cr⁶⁺ in the presence of Pb²⁺ in the electrolyte. The as-deposited PbCrO₄ microrods are single-crystalline in the shape of a long rod with a 1 μm squared cross-section where a well-organized PbCrO₄ growth is achieved with a low nucleation rate. The as-deposited PbCrO₄ microrods absorb UV and visible light (λ < 540 nm), and utilize it for the photoelectrochemical reaction. The photoactivity of PbCrO₄ microrods is greater than that of PbCrO₄ nanorods, having originated from an enhanced minority carrier diffusion length increased by approximately 100 nm. PbCrO₄ microrods with the help of Co–Pi decoration exhibit a noticeable photocurrent (0.5 mA cm⁻² at 1.23 V vs. RHE under 1.5 AMG illumination) and high incident photon-to-current conversion efficiency (30% at λ = 400 nm) for photoelectrochemical water oxidation. Co–Pi decoration also effectively suppresses the formation of Pb⁴⁺ in PbCrO₄, and improves the stability of the as-deposited PbCrO₄ microrods with higher faradaic efficiency, as measured with scanning electrochemical microscopy. Furthermore, the control of electrodeposition potential is found to change the deposit composition between Pb and Cr, which leads to the transition from PbCrO₄ to Pb₂CrO₅.