Mo-BiVO₄/Ca-BiVO₄ Homojunction Nanostructure-Based Inverse Opals for Photoelectrocatalytic Pharmaceutical Degradation under Visible Light

Homojunction engineering has emerged as a potent strategy to evade interfacial stability issues and improve the efficiency of nanostructured metal oxide photocatalysts, though rarely combined with the enhanced light capture ability of three-dimensional macroporous photonic crystal structures. Herein, the formation of nanoscale n-n + homojunctions between different Mo- and Ca-doped BiVO 4 nanocrystals in the skeleton of photonic band gap (PBG) engineered inverse opals is introduced as an advanced approach to simultaneously promote visible light harvesting, electron transport, and charge separation of BiVO 4 nanomaterials for the photoelectrocatalytic degradation of pharmaceutical contaminants of emerging concern. Controlled deposition of BiVO 4 inverse opal films with tailored PBGs was combined with compositional tuning by Mo- and Ca-doping for slow-photon-assisted visible-light-activated (VLA) photocatalysis. The introduction of shallow dopant states in the Mo-, Ca-doped BiVO 4 nanoparticles with relatively weak structural distortions but significantly different donor concentrations resulted in a broad distribution of type-II homojunctions in the nanocrystalline inverse opal walls. Comparative photoelectrochemical evaluation showed that nanostructured homojunction Mo-BiVO 4 /Ca-BiVO 4 photonic films largely outperformed their individual constituents in both photocurrent generation and the VLA photocatalytic degradation rate. Moreover, they exhibited markedly improved performance in the photoelectrocatalytic degradation of tetracycline and ciprofloxacin broad-spectrum antibiotics as well as salicylic acid under visible light, validating their application potential in VLA water remediation by pharmaceutical micropollutants.