No abstract

Material-enhanced heterogonous peroxymonosulfate (PMS) activation on emerging organic pollutant degradation has attracted intensive attention, and a challenge is the electron transfer efficiency from material to PMS for radical production. Herein, an interface architecture of Co­(OH)2 nanosheets growing on the KNbO3 perovskite [Co­(OH)2/KNbO3] was developed, which showed high catalytic activity in PMS activation. A high reaction rate constant (k 1) of 0.631 min–1 and complete removal of pazufloxacin within 5 min were achieved. X-ray photoelectron spectroscopy, X-ray absorption near edge structure spectra, and density functional theory (DFT) calculations revealed the successful construction of the material interface and modulated electronic structure for Co­(OH)2/KNbO3, resulting in the hole accumulation on Co­(OH)2 and electron accumulation on KNbO3. Bader topological analysis on charge density distribution further indicates that the occupations of Co-3d and O-2p orbitals in Co­(OH)2/KNbO3 are pushed above the Fermi level to form antibonding states (σ*), leading to high chemisorption affinity to PMS. In addition, more reactive Co­(II) with the closer d-band center to the Fermi level results in higher electron transfer efficiency and lower decomposition energy of PMS to SO4 •–. Moreover, the reactive sites of pazufloxacin for SO4 •– attack were precisely identified based on DFT calculation on the Fukui index. The pazufloxacin pathways proceeded as decarboxylation, nitroheterocyclic ring opening reaction, defluorination, and hydroxylation. This work can provide a potential route in developing advanced catalysts based on manipulation of the interface and electronic structure for enhanced Fenton-like reaction such as PMS activation.

Nickel oxide (NiO) is considered one of the most promising positive anode materials for electrochromic supercapacitors. Nevertheless, a detailed mechanism of the electrochromic and energy storage process has yet to be unraveled. In this research, the charge storage mechanism of a NiO electrochromic electrode was investigated by combining the in-depth experimental and theoretical analyses. Experimentally, a kinetic analysis of the Li-ion behavior based on the cyclic voltammetry curves reveals the major contribution of surface capacitance versus total capacity, providing fast reaction kinetics and a highly reversible electrochromic performance. Theoretically, our model uncovers that Li ions prefer to adsorb at fcc sites on the NiO(1 1 1) surface, then diffuse horizontally over the plane, and finally migrate in the bulk. More significantly, the calculated theoretical surface capacity (106 mA h g −1 ) accounts for about 77.4% of the total experimental capacity (137 mA h g −1 ), indicating that the surface storage process dominates the whole charge storage, which is in accordance with the experimental results. This work provides a fundamental understanding of transition-metal oxides for application in electrochromic supercapacitors and can also promote the exploration of novel electrode materials for high-performance electrochromic supercapacitors.

Motivated by the extraordinary physical and chemical properties of Janus transition-metal dichalcogenides (TMDs) due to the change of the crystal field originating from their asymmetry structures, the electronic and optical properties of the MoSeTe monolayer in 2H and 1T phases are systematically studied by first-principles calculations, and a detailed comparison with the parental MoSe2 and MoTe2 monolayer is made.