Interfacial Built-In Electric Field at <i>p</i> – <i>n</i> Junction in Bi ₂ Sn ₂ O ₇ /InVO ₄ for Efficient Photocatalytic Degradation and Electrocatalytic HER

Bi2Sn2O7/InVO4 heterostructure has been developed for photocatalytic generation of hydroxyl radical (OH·) and singlet oxygen (1O2), and for electrocatalytic hydrogen evolution reaction (HER). The enhanced photocatalytic generation of OH· and 1O2 is confirmed by electron paramagnetic resonance (EPR) studies by exposing with visible light of λ = 420 nm. It is attributed to the interfacial built-in electric field at the p–n junction of Bi2Sn2O7/InVO4, corroborated by the Fermi energies determined by Kelvin probe force microscopy and by ultraviolet photoelectron spectroscopy (UPS). The enhanced generation of reactive oxygen species accounted for 95.8% photocatalytic degradation of tetracycline hydrochloride within 20 min (pseudo-first-order degradation rate constant of k = 0.105 min–1). Similarly, the efficient electrocatalytic activity of Bi2Sn2O7/InVO4 is revealed from lower HER overpotential (η10 = 121 mV) as compared to the pristine Bi2Sn2O7 or InVO4, and accounted for 95.2% faradaic efficiency. The improved HER is attributable to the mobility of charges facilitated by internal electric field in Bi2Sn2O7/InVO4, adsorption/desorption of hydrogen intermediates at the interface, improved charge kinetics (Tafel slope = 32 mV dec–1), higher electrochemical surface area, and lower charge transfer resistance. It is concluded that Bi2Sn2O7/InVO4 with a built-in electric field at p–n junction is a promising multifunctional material for photocatalytic environmental remediation and for electrocatalytic hydrogen generation via water splitting.