The emergence of antibiotics in the environment, especially in drinking water, poses potential harm to human health. It’s urgent to develop effective methods to remove antibiotics in drinking water. In this work, a series of mesoporous Mn x Co 3−x O 4 nanoparticles with high surface area were successfully synthesized and firstly used as effective stable electro-Fenton catalysts to degrade ciprofloxacin (CIP). The removal of CIP achieved to 100% within 5 h. Experimental and density functional theory (DFT) studies verified the existence of redox pairs of Mn 2+ /Mn 3+ and Co 2+ /Co 3+ . Scanning electrochemical microscopy (SECM) results suggested that the redox reaction capacity of MnCo 2 O 4 was enhanced and the electron transfer rate on the surface of this bimetallic oxide was 2.67 and 1.6 times the number of MnO 2 and Co 3 O 4 , respectively. The effective degradation of CIP was mainly associated with the increased electron transfer rate and advanced redox reactivity owing to the synergistic effect of manganese and cobalt entrapped in the matrix of mesoporous structure which provided more accessible active sites. The degradation intermediates and possible process mechanism were investigated in detail. The reusability of MnCo 2 O 4 -CF cathode was evaluated five cycles with minimal ion leaching which the concentration of Mn and Co in the system was lower than 2.5 and 3.4 ppm, respectively. This work provides further understanding for removal process of organic pollutants by investigation of redox couple and electron transfer rate of the promising MnCo 2 O 4 -CF cathode.
Graphical A Zn−Fe redox flow battery based on choline chloride ethylene glycol deep eutectic solvent is studied. The coulombic efficiency of the cell maintains at about 100 % more than 50 cycles and shows an anomalous variation due to the effect of RO − groups. The study shows the potential of deep eutectic solvent-based flow batteries for large-scale energy storage. Deep eutectic solvents (DESs) were considered as a potential electrolyte because of their low price, harmless to environment and wider electrochemical window potential compared to water. In this work, Fe(III)/Fe(II) and Zn(II)/Zn redox couples were used as the positive and negative active materials, respectively, in a DES system using choline chloride and ethylene glycol in a molar ratio of 1 : 2 (ethaline). The possible working mechanism of the battery was studied by cyclic voltammetry, spectroscopic and simulation methods. The effects of different temperatures, concentrations of zinc ions in the anolyte and current densities on battery performance were evaluated. The results showed that the designed zinc-iron battery should preferably be operated at a current density of 0.5 mA cm −2 and the temperature of 313~323 K, which will improve the energy efficiency and maintain a high coulombic efficiency. The variation of cycle performance test presents a different pattern from the usual batteries, which is due to the effect of RO − group. At 313 K and 0.5 mA cm −2 , the coulombic efficiency increases from 14.1 % to 100.2 % after 46 cycles, and then remains at about 100 % during the rest 54 cycles, which demonstrates a good cycle stability of DES-based zinc-iron battery.
Gel-based ionic thermoelectric (i-TE) conversion systems have attracted more attention to harvest energy from ambient waste heat to power sensors in IoT systems, due to their high ionic thermopower, cost-effectiveness, and environmental friendliness. However, their thermoelectric performance, particularly output power density, remains low, hindering their further application. To date, there is still a lack of an effective strategy to reverse this serious situation. Herein, we originally designed an ionic thermoelectric-electrochemical (i-TE-EC) cell by combining two asymmetric gels into a double sandwich structure, resulting in high thermoelectric performance. By tailoring gel compositions, including the concentration and ratio of redox couples as well as additive contents, a maximum output power density Pmax/(ΔT)2 of 10.0 mW m−2 K−2, a cell ionic thermopower of 5.2 mV K−1, and an energy density of 3.4 J m−2 K−2 in two hours were obtained at 313 K for the i-TE-EC cell Gp | G-m/n FeCN4−/3− | Gp | G-x/y I−/I3−-z CF3SO3K | Gp (m/n = 0.175/0.025 M, x/y = 0.10/0.05 M, z = 0.4 M). Moreover, Pmax/(ΔT)2 increased to a higher value of 20.5 mW m−2 K−2 for the i-TE-EC cell using a CEM as a built-in electrode. A gel-device assembled by nine single i-TE-EC cells connected in series generated a voltage of 1.55 V and a high Pmax/(ΔT)2 of 5.2 mW m−2 K−2 at 313 K and ΔT = 5 K. This work provides a promising route for improving the gel-based thermoelectric performance, available for other energy conversion systems.
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