Switchable Photoelectrochemistry in Thin Films of SbSI Microrods

Abstract

Antimony sulfoiodide (SbSI) is a ferroelectric semiconductor with a narrow band gap, recognized for its potential in photoelectrocatalytic applications. In this study, thin-film electrodes composed of SbSI microrods were fabricated and characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffractometry (XRD), and diffuse reflectance spectroscopy (DRS), confirming the formation of porous films consisting of crystalline microrods. Electrochemical (EC) and photoelectrochemical (PEC) measurements revealed high photoactivity, with photocurrent generated in both anodic and cathodic regions. The PEC response was highly sensitive to film thickness, electrolyte pH, and oxygen concentration. Optimal photocurrent occurred at a ∼125 nm thickness, while acidification enhanced cathodic photocurrent and inhibited anodic photocurrent. O₂ saturation of the electrolyte stabilized and boosted cathodic photocurrent. SbSI microrods underwent a ferroelectric-to-paraelectric phase transition between 14 and 20°C, which resulted in an increase in both dark current and photocurrent. Photocurrent spectroscopy enabled extraction of direct and indirect band gaps, with the indirect gap exhibiting a distinct shift (∼0.03 eV) across the transition. These results establish SbSI microrod films as promising switchable, narrow-bandgap photoelectrocatalysts, with PEC performance tunable via structural phase transitions and environmental parameters, paving the way for their integration into responsive energy conversion and sensing systems.