On-site H2O2 electrogeneration at a CoS2-based air-diffusion cathode for the electrochemical degradation of organic pollutants

Abstract

This work reports, for the first time, the manufacture and use of an air-diffusion cathode containing CoS 2 nanoparticles to enhance the H 2 O 2 electrogeneration. Hydrothermal synthesis allowed the formation of crystalline CoS 2 with pyrite structure, either unsupported or supported on carbon nanotubes. Both kinds of catalysts were characterized by X-ray diffraction and FE-SEM combined with energy dispersive X-ray analysis. The use of carbon nanotubes as support led to a remarkable enhancement of the CoS 2 stability, as deduced from cyclic voltammetry analysis. The electrochemical activity of the CoS 2-based materials towards the oxygen reduction reaction (ORR) in acidic medium was examined by potentiodynamic techniques using a rotating disk electrode. Both catalysts showed activity towards the ORR, being predominant the twoelectron pathway to form H 2 O 2 as main product. A novel CoS 2-on-carbon nanotubes catalyzed air-diffusion cathode, as well as an uncatalyzed one made for comparison, was manufactured to electrogenerate H 2 O 2 under galvanostatic conditions in an undivided two-electrode cell. A concentration of 56.9 mM was found with the former cathode at 100 mA cm − 2 , much > 32.0 mM found with the uncatalyzed cathode. This informs about the high performance of the CoS 2 nanoparticles to promote the two-electron ORR. Finally, the treatment of aqueous solutions of the anaesthetic tetracaine at pH 3.0 and 100 mA cm − 2 by electro-oxidation and photoelectro-Fenton processes demonstrated the viability of the manufactured CoS 2-based cathode for water treatment.

Hydrogen peroxide generation from O2 electroreduction for environmental remediation: A state-of-the-art review

“…Various pharmaceutical drugs have been detected in different water sources in recent years, such as ibuprofen (Skoumal et al, 2009;Zhou et al, 2018b), sulfadiazine , tetracaine (Ridruejo et al, 2018), amoxicillin (Elmolla and Chaudhuri, 2010;Garza-Campos et al, 2018), and ciprofloxacin (Divyapriya et al, 2018). Some of the drugs are mutagenic and carcinogenic.…”

TiO2/Au/TiO2 multilayer thin-film photoanodes synthesized by pulsed laser deposition for photoelectrochemical degradation of organic pollutants

“…The performance of conventional PEC can be enhanced by employing a cathode with great ability to electrogenerate H 2O2 from two-electron O2 reduction. This reaction is especially efficient at carbonaceous substrates such as supported particles [8][9][10][11], fibers [12,13], nanotubes [14,15], graphene [16,17], felts [18,19] or air-diffusion materials [20].…”

Enhanced electrocatalytic production of H2O2 at Co-based air-diffusion cathodes for the photoelectro-Fenton treatment of bronopol

“…developed by our group to degrade the anaesthetic tetracaine [35], showing Co particles the best activity as compared to Cu, Ce, Mn or Fe-modified air-diffusion cathodes [36]. Barros et al.…”

“…Here, MWCNTs decorated with Co-based catalyst in the form of sulfide, very efficient for H2O2 production at small scale [35], were prepared as a preliminary step for the subsequent manufacture of air-diffusion cathodes with carbon cloth as substrate. For the first time, this type of cathode has been used to electrogenerate H2O2 and treat an organic pollutant like bronopol in 0.050 M Na2SO4 at pH 3.0 by EO-H2O2, EF, PEF and SPEF using a pre-pilot plant.…”