An electrochemical technique for the reduction of aromatic nitrocompounds in H2SO4 medium on thermally coated Ti/TiO2 electrodes

Highly Selective Electroreduction of Nitrobenzene to Aniline by Co-Doped 1T-MoS2

The selective electrocatalytic reduction of nitrobenzene (NB) to aniline demands a desirable cathodic catalyst to overcome the challenges of the competing hydrogen evolution reaction (HER), a higher overpotential, and a lower selectivity. Here, we deposit Co-doped 1T MoS2 on Ti mesh by the solvothermal method with different doping percentages of Co as x % Co-MoS2 (where x = 3, 5, 8, 10, and 12%). Because of the lowest overpotential, lower charge-transfer resistance, strong suppression of the competing HER, and higher electrochemical surface area, 8% Co-MoS2 achieves 94% selectivity of aniline with 54% faradaic efficiency. The reduction process follows first-order dynamics with a reaction coefficient of 0.5 h-1. Besides, 8% Co-MoS2 is highly stable and retains 81% selectivity even after 8 cycles. Mechanistic studies showed that the selective and exothermic adsorption of the nitro group at x % Co-MoS2 leads to a higher rate of NB reduction and higher selectivity of aniline. The aniline product is successfully removed from the solution by polymerization at FTO. This study signifies the impact of doping metal atoms in tuning the electronic arrangement of 1T-MoS2 for the facilitation of organic transformations.

Efficient Electrochemical Reduction of Nitrobenzene by Defect-Engineered TiO2-x Single Crystals

TiO2 is a typical semiconductor and has been extensively used as an effective photocatalyst for environmental pollution control. But it could not be used as an electrochemical reductive catalyst because of its low electric conductivity and electrocatalytic activity. In this work, however, we demonstrate that TiO2 can act as an excellent cathodic electrocatalyst when its crystal shape, exposed facet and oxygen-stoichiometry are finely tailored by the local geometric and electronic structures. The defect-engineered TiO2-x single crystals dominantly exposed by high-energy {001} facets exhibits a high cathodic activity and great stability for electrochemical reduction of nitrobenzene, a typical refractory pollutant with high toxicity in environment. The single crystalline structure, the high-energy {001} facet and the defective oxygen vacancy of the defect-engineered TiO2-x single crystals are found to be mainly responsible for their cathodic superiority. With the findings in this work, a more practical non-Pd cathodic electrocatalyst could be prepared and applied for electrocatalytic reduction of refractory pollutants in water and wastewater, and extend the promising applications of TiO2 in the fields of environmental science.

Efficient reduction of nitrobenzene to aniline with a biocatalyzed cathode

Nitrobenzene (NB) is a toxic compound that is often found as a pollutant in the environment. The present removal strategies suffer from high cost or slow conversion rate. Here, we investigated the conversion of NB to aniline (AN), a less toxic endproduct that can easily be mineralized, using a fed-batch bioelectrochemical system with microbially catalyzed cathode. When a voltage of 0.5 V was applied in the presence of glucose, 88.2 ± 0.60% of the supplied NB (0.5 mM) was transformed to AN within 24 h, which was 10.25 and 2.90 times higher than an abiotic cathode and open circuit controlled experiment, respectively. AN was the only product detected during bioelectrochemical reduction of NB (maximum efficiency 98.70 ± 0.87%), whereas in abiotic conditions nitrosobenzene was observed as intermediate of NB reduction to AN (decreased efficiency to 73.75 ± 3.2%). When glucose was replaced by NaHCO(3), the rate of NB degradation decreased about 10%, selective transformation of NB to AN was still achieved (98.93 ± 0.77%). Upon autoclaving the cathode electrode, nitrosobenzene was formed as an intermediate, leading to a decreased AN formation efficiency of 71.6%. Cyclic voltammetry highlighted higher peak currents as well as decreased overpotentials for NB reduction at the biocathode. 16S rRNA based analysis of the biofilm on the cathode indicated that the cathode was dominated by an Enterococcus species closely related to Enterococcus aquimarinus.

Treatment methods for the remediation of nitroaromatic explosives

The production and use of nitroaromatic explosives for military operations have resulted in their dissemination into the environment, where their presence in waterways and soil poses an ecological and health hazard. This paper reviews technologies that are available or under investigation to remediate areas contaminated with these compounds.