Preparation and performance of aerogel-based BiOI/TiO2 heterojunction photoelectrocatalytic electrodes

TiO2/BiOI/CA electrodes with improved conductivity, reduced photoelectron–hole recombination rates, and increased reaction sites based on p–n type heterojunctions were constructed on carbon aerogels (CA) as photoelectrode substrates. Characterization based on ultraviolet-visible diffuse reflectance spectroscopy, photocurrent measurements, and impedance analysis showed that the TiO2/BiOI/CA photoelectrode with a Ti/Bi mole ratio of 0.4 exhibited the best visible light absorption, lowest photogenerated electron–hole pair recombination rate, and strongest photocatalytic degradation, with 90.4% degradation of phenol under 120 min of light. Moreover, the stability of this electrode remained at a high level. This was mainly because the energy levels of TiO2 and BiOI matched each other and the p–n heterojunction formed adjusted the energy band structure of the composite material, widened the electron transfer path, formed an internal electric field between the phase interfaces, had a higher electron transfer rate, and reduced the photogenerated electron–hole recombination rate. Since ˙OH and ˙O2− are the main active substances in the degradation of phenol, the TiO2/BiOI/CA photoelectrodes had higher degradation efficiency than BiOI/CA electrodes. This study provides a unique concept for the treatment of organic pollutant wastewater and electrode design for photoelectrocatalysis.