Enhanced Fenton-like Oxidation of As(III) over Ce–Ti Binary Oxide: A New Strategy to Tune Catalytic Activity via Balancing Bimolecular Adsorption Energies

The development of catalysts for oxidation of aqueous contaminants has long been relying on trial-and-error strategies due to lack of activity-tuning principles. Herein, Fenton-like oxidation of As(III) as a chemisorbed model contaminant over a series of fabricated CexTi1-xO2 catalysts with tunable structures was investigated. The activity of CexTi1–xO2 showed a volcano-shape dependency on Ce molar fraction, peaking at Ce0.25Ti0.75O2 (x = 0.25) with 6.32–6.36 times higher activity and 2.67–2.94 times higher specific activity compared with CeO2 and TiO2. The non-radical surface hydroperoxo complexes were experimentally substantiated as the dominant oxidant species on Ce0.25Ti0.75O2, which enabled a high efficiency of H2O2 utilization (99.1%). Under the verified Langmuir–Hinshelwood mechanism, the microkinetic model for the catalytic oxidation was established, and thus, the quantitative relationship between activity and adsorption energies for bimolecular chemisorption reactions was elucidated. Theoretically, a catalyst with identical adsorption energies toward both chemisorbed reactants tends to obtain the highest activity. Through DFT calculation, the highest activity of Ce0.25Ti0.75O2 was rationally interpreted by the balanced adsorption energies toward As(III) and H2O2, which was attributed to the shifted electronic density of states induced by Ce doping. This study provides a potent strategy to tune the catalytic activity of bimolecular chemisorption reactions.