Advances in photo-electrocatalytic materials for environmental protection: Application to water and wastewater treatment

Abstract

This work explores the elimination of Rhodamine B (Rh B) via electrocatalytic and electro-photocatalytic processes, employing Ba2SnO4 double perovskite as the anodic material. Ba2SnO4 was synthesized via hydrothermal method and comprehensively characterized using structural, optical, and electrochemical techniques to evaluate its potential for Rhodamine B oxidation. X-ray diffraction confirmed the formation of a single-phase tetragonal structure (space group I4/mmm), with spherical particles approximately 50 nm in diameter. Dynamic light scattering (DLS) indicated an average particle size of 0.35 µm, and zeta potential measurements showed a surface charge of −5 mV. Scanning electron microscopy revealed a porous surface texture. Optical characterization via diffuse reflectance spectroscopy identified a direct bandgap of 3.23 eV, attributed to O2− (2p) to Sn4+ (5 s) charge transfer. The material demonstrated high chemical resilience across a wide pH range. Mott-Schottky analysis confirmed its n-type semiconducting nature, likely due to oxygen vacancies. The observed low electron mobility was linked to the narrow conduction band formed by Sn4+: 5 s states, with an activation energy of 18 meV, indicative of small polaron hopping as the dominant transport mechanism. The current density–voltage (J–E) curve in NaCl (10−2 M) displayed minimal hysteresis, characteristic of a chemically stable system akin to a chemical diode. In electrocatalytic tests, ∼65% of Rh B was degraded under a direct current of 150 mA, showcasing antibacterial effects. This performance was significantly enhanced under combined electro-photocatalytic conditions, reaching ∼95% degradation under simultaneous exposure to sunlight and electrical bias