Revisiting the Role of Peroxymonosulfate in TiO₂-Mediated Photocatalytic Oxidation: Dependence of Kinetic Enhancement on Target Substrate and Surface Platinization

Abstract

An enhancing effect of peroxymonosulfate (PMS) on photocatalytic activity has previously been demonstrated, but the research focus was concentrated primarily on the extent to which treatment efficiency was improved. To further comprehend the role of PMS, this study examined the TiO2 photocatalytic systems in the presence of PMS for the oxidation of diverse organics and showed that the extent of performance enhancement via PMS addition was substrate-dependent. This resulted from the involvement of multiple oxidants owing to the dual role of PMS as an electron acceptor and a radical precursor, confirmed in the open circuit potential shifts and electron paramagnetic resonance spectra. Surface platinization, typically adopted to modulate charge carrier dynamics in photocatalysis, caused the nonphoton-driven degradative pathway, i.e., mediated electron transfer involving PMS as a two-electron acceptor, and promoted the one-electron reduction of PMS to sulfate radicals (SO4 •–). The contribution of SO4 •– was assessed based on efficiencies for decarboxylation and hydroxylation, isomer distribution in the hydroxylated intermediates, the quenching effect of alcohols, and net conversion of methanol to formaldehyde. Relying on the selective reactivity of Pt-activated PMS, Pt-TiO2/PMS outperformed bare TiO2/PMS in oxidatively treating the binary mixtures of organics and enabled effective organic degradation under periodic light irradiation.

Mn-Enhanced Cobalt Silicate-Activated Peroxymonosulfate for Tetracycline Degradation: Inheriting Merit and Offsetting Deficiency of Oxygen Vacancies

“…Moreover, the TC degradation experiments with D 2 O acting as the solvent also verified the existence of 1 O 2 (Figure S12). The results of EPR with DMPO serving as spin traps revealed the existence of O 2 –• in CoSi and MnCoSi/PMS systems (Figure c). , Moreover, the characteristic signals of SO 4 –• , • OH, and 1 O 2 could be observed in both MnCoSi/PMS and CoSi/PMS systems (Figure d,e). − As shown in Figure S13, the addition of PMS and TC made the current drop slightly, indicating that there was no electron transfer path in the system . When PMSO was added, the degradation of TC was almost unaffected, which ruled out the contribution of high-valent metal species (Figure S14).…”

Cost-Effective and Highly Efficient Manganese-Doped MoS2 Nanosheets as Visible-Light-Driven Photocatalysts for Wastewater Treatment

“…As a result, the metal dopant transports electrons and holes created by the light beam to the reaction surface, preventing their recombination rate and thus enhancing photodegradation. A pseudo-first-order kinetic equation can be used to calculate the apparent rate constant of kinetic degradation for samples with different concentrations. , The investigation showed that the rate constants are calculated to be 0.00413, 0.0097, 0.0226, 0.06, and 0.07442 min –1 for MoS 2 , 5% Mn-doped MoS 2 , 10% Mn-doped MoS 2 , 15% Mn-doped MoS 2 , and 20% Mn-doped MoS 2 , respectively (shown in Figure a).…”

Edge Rich Ultrathin Layered MoS2 Nanostructures for Superior Visible Light Photocatalytic Activity

“…Thus, the as-synthesized MoS 2 catalysts can be readily used for catalytic applications without further processing. 55,56 However, the ferromagnetism of a MoS 2 system is induced by vacancy, deformation, or zigzag edges. 57 SI Figure S4a,4b present the magnetization curves (M-H) of the MoS 2 nanoflowers and nanosheets respectively measured at ambient temperatures (∼300 K).…”

“…The study shows that the atomic ratio of the Mo:S changed from 1:1.189 to 1:1.975, implying direct evidence that the number of unsaturated sulfur atoms when the structure changed from nanosheets to nanoflowers. , This is possible for two reasons (1) formation of few-nanometer MoS 2 nanoflowers having ultrathin sharp edges (2) usage of CH 3 CSNH 2 as a precursor may enhance the number of unsaturated sulfur atoms at the exposed edge during synthesis. Thus, the as-synthesized MoS 2 catalysts can be readily used for catalytic applications without further processing. , …”