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

摘要

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 Ce_xTi_(1-x)C_2 catalysts with tunable structures was investigated. The activity of Ce_xTi_(1-x)C_2 showed a volcano-shape dependency on Ce molar fraction, peaking at Ce_(0.25)Ti_(0.75)O_2 (x=0.25) with 6.32-6.36 times higher activity and 2.67-2.94 times higher specific activity compared with CeO_2 and TiO_2. The non-radical surface hydroperoxo complexes were experimentally substantiated as the dominant oxidant species on Ce_(0.25)Ti_(0.75)O_2, which enabled a high efficiency of H_2O_2 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 Ce_(0.25)Ti_(0.75)O_2 was rationally interpreted by the balanced adsorption energies toward As(III) and H_2O_2, 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.