Organic carboxylic acid fuels as structural modulators in combustion-synthesized CdFe2O4: enhanced pH-dependent photocatalytic performance.

Visible light-responsive CdFe2O4 photocatalysts were synthesized via a one-step combustion route using a series of structurally distinct carboxylic acid-based fuels, enabling deliberate modulation of nanostructure and optoelectronic properties. The functional groups and molecular architecture of the fuels played a crucial role in governing combustion behavior, which in turn dictated crystallite growth, surface morphology, and bandgap tuning in the resulting CdFe2O4 nanoparticles. These tailored photocatalysts were evaluated for malachite green (MG) degradation in a Vis-light/CdFe2O4/H2O2 system, exhibiting pseudo-first-order kinetics with apparent rate constants enhanced by up to 31-fold as a function of solution pH. MG degradation proceeded via reactive oxygen species (ROS), including h⁺, ·OH, and O2⁻·, with h⁺ identified as the dominant oxidative species. The system showed strong pH responsiveness and sensitivity to inorganic salts ions, attributable to fuel-dependent adjustments in surface charge and morphology. Furthermore, the CdFe2O4 displayed excellent stability, retaining high photocatalytic activity over nine consecutive reuse cycles.