Insight into the role of reactive species on catalyst surface underlying peroxymonosulfate activation by P-Fe2MnO4 loaded on bentonite for trichloroethylene degradation

In this study, bentonite supporting phosphorus-doped Fe2MnO4 (BPF) was synthesized and applied for PMS activation to degrade TCE. Morphology and structure characterization results indicated the successfully synthesized of BPF, and the BPF/PMS system not only featured high TCE removal (97.4%) but also high reaction rate constant (kobs = 0.0554 min-1) and PMS utilization (70.4%, kobs = 0.0228 min-1). According to the results of various experiments, massive oxygen vacancies on P-Fe2MnO4 alter its charge balance and facilitate the electron transfer process named adjacent transfer (direct electron capture by adsorbed PMS from adjacent TCE). Mn(III) is the main adsorption site for PMS, and the hydroxyl groups on the catalyst (Fe sites of P-Fe2MnO4, Si and Al sites of bentonite) can also offer binding sites for PMS. The hydrogen-bonded PMS on Fe(III) and Mn(III) sites will subsequently accept the discharged electrons to generate free radicals and high-valent metal species. Meanwhile, electron loss of HSO5- that chemically bonded to hydroxyl groups on bentonite will generate SO5•-, which will further produce 1O2 through self-bonding. the active species on the catalyst surface contribute 65% of TCE degradation in the heterogeneous catalytic oxidation system.

Cold plasma synthesis of phosphorus-doped CoFe2O4 with oxygen vacancies for enhanced OER activity

Spinel-type metal oxides are promising electrocatalysts for the oxygen evolution reaction (OER) due to their unique electronic structure and low cost. Herein, we induced oxygen vacancies and doped phosphorus into CoFe2O4 using cold plasma. The abundant oxygen vacancies enhanced hydrophilicity and modified the electronic structure of CoFe2O4, while the phosphorus doping formed numerous new active centers. The doped P and formed FeP promoted the charge transfer and improved the conductivity of the catalyst. The phosphorus-doped CoFe2O4 exhibited exceptional OER activity with an overpotential of 180 mV at 10 mA cm-2 and a Tafel slope of 65.8 mV dec-1 in an alkaline electrolyte. DFT calculations confirmed that phosphorus doping can improve the charge distribution near the Fermi level and optimize the d-band center position.

Porous MCo2O4(M = Zn, Cu, Fe, Mn) as high efficient bi-functional catalysts for oxygen reduction and oxygen evolution reaction

High-efficiency bi-functional electrocatalysts with long-term stability are critical to the development of many kinds of fuel cells, because that the performance of battery is limited by the slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this work, porous MCo₂O₄(M = Zn, Cu, Fe, Mn) were prepared by hydrothermal method with NH₄F and urea as surfactants. FeCo₂O₄with porous structure has more oxygen defects and the larger specific surface area than other MCo₂O₄(M = Zn, Cu, Mn), and it not onlysupplies more active sites but also avails the transmission of electrolyte and O₂in the process of ORR and OER in 0.1 M KOH aqueous solution. Porous FeCo₂O₄electrode material produces less intermediate H₂O₂, and its ORR is mainly controlled by a 4e^-reaction path. Compared with commercial Pt/C, the prepared FeCo₂O₄has comparable ORR activity and excellent OER activity. At the same time, the stability of FeCo₂O₄to ORR is significantly higher than that of commercial Pt/C. The porous FeCo₂O₄was prepared by facile synthesis procedure could be a potential promising bi-functional catalyst due to its high electrocatalytic activities and long-term stability for both the ORR and OER.

Construction of bimetallic FeCo–SA/DABCO nanosheets by modulating the electronic structure for improved electrocatalytic oxygen evolution

For energy conversion and storage, the electrochemical oxygen evolution process (OER) is the crucial half-reaction process.