Outlook on Single Atom Catalysts for Persulfate-Based Advanced Oxidation

Abstract

Single atom catalysts (SACs) have emerged as a promising catalyst material architecture for energy, chemical, and environmental applications. In the past several years, SACs have been increasingly explored for persulfate-based advanced oxidation processes (AOPs) due to their superior persulfate activation and pollutant degradation performance compared to benchmark dissolved ion and nanoparticle catalysts. However, there still exist uncertainties on the mechanism of persulfate activation by SACs, which involves a complex interplay of sulfate and hydroxyl radicals, singlet oxygen, high-valent metal species, and/or mediated electron transfer. Questions also remain as to how persulfate ions molecularly align on the single atom site, how persulfate ions are converted into reactive species, and what design parameters lead to higher efficiency for persulfate activation and pollutant degradation. In this critical review, we examine past SAC materials employed for persulfate-based AOPs and discuss how they function differently compared to their ion and nanoparticle counterparts. We further our discussion on current limitations, opportunities, and future research needs in (i) filling the knowledge gaps in the mechanisms of persulfate-SAC interactions; (ii) augmenting fundamental research with theoretical simulation and in situ characterization techniques; (iii) improving material design tailored for environmental applications; and (iv) proactively considering the challenges associated with engineering practices and complex water matrixes.

Grand challenges present great opportunities in environmental catalysis

“…Solar-driven reduction of CO 2 into chemicals and fuels offers the promise of addressing global warming and energy crisis simultaneously. Taking advantage of nano-clusters and single-atom catalysis, more efficient catalysts are also being developed to activate H 2 O 2 and persulfate for environmental applications of AOPs (Wu and Kim, 2022), as well as to innovate catalysis for emission control and other applications (Li et al, 2020).…”

Current Mechanism of Peroxymonosulfate Activation by Cobalt-Based Heterogeneous Catalysts in Degrading Organic Compounds

“…Due to the excellent activation ability of Co, doping Co into other materials can improve the activity of the catalyst. In addition to metal materials, incorporating Co into carbon-based nanosheet materials has become the mainstream approach to prevent metal ion leaching, enhance atom utilization, and facilitate catalyst recovery. ,, When Co is doped onto carbon nitride nanosheets, the unique chemical properties of Co and the full exposure of Co–N sites result in high catalytic activity . Li et al calculated the adsorption properties of pure Co crystal and the Co–C 3 N 5 system.…”

Single-Atom MnN5 Catalytic Sites Enable Efficient Peroxymonosulfate Activation by Forming Highly Reactive Mn(IV)–Oxo Species

“…Single-atom catalysts (SACs) have emerged as promising heterogeneous catalysts for PMS activation due to their utmost atom utilization efficiency and high selectivity for diverse catalytic reactions. ,− Especially, four-nitrogen coordinated SACs display significantly high selectivity in HVMO generation during PMS activation. ,, For example, electron-depleted CuN 4 /C–B was reported to boost PMS activation and form Cu­(III)–OH reactive species for bisphenol A removal . Also, Fe­(IV)–HVMO was found to be the major oxidizing species in FeN 4 single-site catalyzed PMS activation, and it exhibited selective reactivity for oxidizing organic contaminants of emerging concern …”