SbSI Nanocrystals: An Excellent Visible Light Photocatalyst with Efficient Generation of Singlet Oxygen

Antimony sulfoiodide (SbSI) is commonly known as a prototypical ferroelectric semiconductor. We report herein a top-down strategy of ball-milling followed by size selective centrifugation to prepare SbSI nanocrystals (NCs). Taking the well dispersed SbSI NCs of the average size of 80 nm as photocatalyst, a record high visible light efficiency in photodegradation of methyl orange (MO) in water was achieved. By using a 300 W xenon lamp with a 420 nm cutoff filter and with the SbSI NCs of 1 g/L, the MO solution of 30 mg/L can be degraded ∼99% in 10 s. The pseudo-first-order rate constant (k) of the photodegradation is k = 0.42 s^-1. For high concentrated MO of 150 mg/L, it can be ∼99% degraded in 30 s at an elevated temperature of 65 °C (k = 0.15 s^-1). With further increase of the SbSI NCs concentration to 4 g/L, the 150 mg/L MO can be ∼99% degraded in 1 min at room temperature (k = 0.095 s^-1). The small size of the SbSI NCs and efficient generation of singlet oxygen were found to be the key factors for the outstanding performance.