Sustainable removal of N2O by mediated electrocatalytic reduction at ambient temperature electro-scrubbing using electrogenerated Ni(I) electron mediator

Enhanced sustainable electro-generation of a Ni (I) homogeneous electro-catalyst at a silver solid amalgam electrode for the continuous degradation of N2O, NO, DCM, and CB pollutants

This paper reports the sustainable and enhanced generation of a Ni(I) active electro-catalyst using AgSAE as a cathode material for the sustainable degradation of N₂O, NO, dichloromethane (DCM), and chlorobenzene (CB) by electroscrubbing in a series operation. The AgSAE electrode showed 1.66 times higher Ni(I) formation than the Ag metal electrode. The AgSAE achieved 20% ± 2% Ni(I) generation in a highly concentrated alkaline medium, whereas Ag metal only achieved 12% ± 2% Ni(I) generation at the same current density. Electrochemical impedance spectroscopy and voltammetric studies determined that the kinetics of the charge-transfer reaction was also preferential at the AgSAE, with the cathodic peak at -1.26 V vs. Ag/AgCl confirming Ni(I) formation. Initially, the change in the oxygen reduction potential and reduction efficiency of Ni(I) confirmed the removal of N₂O, NO, DCM and CB. In addition, the gas Fourier transform infrared (FTIR) spectrum revealed 99.8% removal efficiency of toxic pollutants. Therefore, the regeneration of Ni(I) confirmed the sustainable removal of toxic pollutants. Furthermore, the FTIR spectra revealed the formation of NH₃ during the reduction of N₂O and NO. On the other hand, DCM and CB were reduced to benzene derivatives in the solution phase. In addition, a plausible reduction mechanism was derived. As a result, the AgSAE cathode exhibited two-fold higher removal efficiency of N₂O, NO, DCM, and CB than the previously reported electrodes.

Strong Structural Modification of Gd to Co3O4 for Catalyzing N2O Decomposition under Simulated Real Tail Gases

In this paper, Gd-promoted Co₃O₄ catalysts were prepared via a facile coprecipitation method for low-temperature catalytic N₂O decomposition. Due to the addition of Gd, the crystallite size of Co₃O₄ in the Gd_0.06Co catalyst surprisingly decreased to 4.9 nm, which is much smaller than most additive-modified Co₃O₄ catalysts. This huge change in the catalyst's textural structure endows the Gd_0.06Co catalyst with a large specific surface area, plentiful active sites, and a weak Co-O bond. Hence, Gd_0.06Co exhibited superior activity for catalyzing 2000 ppmv N₂O decomposition, and the temperature for the complete catalytic elimination of N₂O was as low as 350 °C. Meanwhile, compared with pure Co₃O₄, E_a decreased from 77.4 to 46.8 kJ·mol^-1 and TOF of the reaction increased from 1.16 × 10^-3 s^-1 to 5.13 × 10^-3 s^-1 at 300 °C. Moreover, Gd_0.06Co displayed a quite stable catalytic performance in the presence of 100 ppmv NO, 5 vol % O₂, and 2 vol % H₂O.

Tetracyanonickelate (II)/KOH/reduced graphene oxide fabricated carbon felt for mediated electron transfer type electrochemical sensor for efficient detection of N2O gas at room temperature

N₂O is the most significant anthropogenic greenhouse gas, which cause the ozone depletion. Hence, the room temperature detection of N₂O is highly desirable. In this work, The TCN(II)-KOH-rGO/CF modified electrode was successfully fabricated by drop coating method. The synthesized electrode was successfully characterized by SEM, TEM, FT-IR and XRD. The sensor electrode was used to detect different N₂O concentration in flow conditions at room temperature. TCN(II)-KOH-rGO/CF modified electrode showed high sensitivity towards N₂O, a wide range from 1ppm to 16 ppm and low detection of 1 ppm N₂O were achieved for the TCN(II)-KOH-rGO/CF modified electrode. The limit of detection and the response towards this nitrogen oxide is competitive to other sensing methods. In addition, the sensitivity of the electrochemical sensor electrode was compared with the online Gas Chromatography. Additionally, the selectivity of the working electrode was analyzed and specified. The working electrode stability was analyzed for more than 30 days shows good stability. The fabricated TCN(II)-KOH-rGO/CF electrode is easier to prepare to get excellent analytical performance towards N₂O. Hence, the proposed TCN(II)-KOH-rGO/CF electrode could be the suitable material for detection of N₂O in the real site process.

Sustainable generation of homogeneous Fe(VI) oxidant for the room temperature removal of gaseous N2O by electro-scrubbing process

A high valent Fe(VI) homogenous catalyst was synthesized following electrochemical route for the efficient removal of a greenhouse gas (N₂O) by mediated electro catalytic oxidation (MEO) in an electro-scrubbing process. This paper describes the room temperature degradation of N₂O using a consistently generable hexavalent Fe(VI) homogenous catalyst. The ferrate (VI) was electrochemically generated by employing a membrane divided cell, and quantified by monitoring the changes in the ORP (oxidation/reduction potential) along with a potentiometric titration by the chromite method using chromium Cr(III) as a titrant. In addition, the formation of ferrate (VI) was confirmed through UV-visible spectroscopy study results. The change in the ORP values from 360 mV to 253 mV and the change in concentration of electrogenerated Fe(VI) from (4 mM) to (2.9 mM) during N₂O removal confirmed that N₂O removal followed a mediated electrocatalytic oxidation (MEO) process. An online FTIR gas analyzer study results revealed approximately 90% degradation efficiency of N₂O during the MEO process in a gas mixture containing 5 ppm N₂O at a 0.2 L min^-1 gas flow rate at ambient temperature. The energy efficiency for N₂O removal using the Fe(VI) mediator resulted in ten times higher (0.0021 g kWh^-1) than the existing MER (0.00063 g kWh^-1) process. The possible consistent generation of a homogenous electrocatalyst and its degradation of greenhouse gases at ambient temperature process can be explored to a more practical level.

Direct catalytic decomposition of N2O over bismuth modified NiO catalysts

Direct catalytic decomposition is a promising technology to control the emission of nitrous oxide (N₂O) during fossil fuel combustion and various chemical industries. In this study, a series of NiO catalysts modified with different metal oxides (M_aNiO_b) were prepared by the co-precipitation method and employed for the direct catalytic decomposition of N₂O. Bismuth (Bi) species was confirmed to be the most optimal promoter and the Bi_0.1NiO_1.15 catalyst with a Bi/Ni molar ratio of 0.1 exhibited the best activity over the temperature range of 300-450 °C. The addition of Bi species also promoted the steam resistance capability of the NiO catalyst. Moreover, the physicochemical properties of pure and Bi-modified NiO catalysts were further determined by several characterization methods. The surface areas and capacity of oxygen adsorption/desorption over the catalyst were noticeably improved with the doping of Bi species. Besides, the presence of doped-Bi facilitated the creation of both Ni³⁺ and surface oxygen vacancies on NiO, which promoted the performance of N₂O decomposition. Whereas, the excessive Bi species would accumulate to form large Bi₂O₃ grains, which diminished the surface areas and covered the active sites on the catalysts, leading to the rapid degradation of N₂O catalytic decomposition.