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The present work investigates the electrocatalytic performance of two different morphologies of boron doped-diamond film electrode (microcrystalline diamond - MCD, and nanocrystalline diamond - NCD) used in electrochemical oxidation for the removal of the antibiotic ciprofloxacin (CIP). A thorough study was conducted regarding the formation of the MCD and NCD films through the adjustment of methane in CH4/H2 gas mixture, and the two films were compared in terms of crystalline structure, apparent doping level, and electrochemical properties. The physicochemical results showed that the NCD film had higher sp2 carbon content and greater doping level; this contributed to improvements in its surface roughness, as well as its specific capacitance and charge transfer, which consequently enhanced its electrocatalytic activity in comparison with the MCD. The results obtained from CIP removal and mineralization assays performed in sulfate medium also showed that the NCD was more efficient than the MCD under all the current densities investigated. The effects of CIP concentration and the evolution of the final by-products, including short-chain carboxylic acids and inorganic ions, were also investigated. The electrochemical performance of the NCD was evaluated in different aqueous matrices, including chloride medium, real wastewater and simulated urine. The application of the NCD led to complete or almost complete CIP degradation, regardless of the medium employed. The kinetic constant rates obtained under the different media investigated were as follows: synthetic urine (0.0416 min−1 – R2 = 0.991)

Palladium nanoparticles have been studied extensively as catalysts for the direct synthesis of hydrogen peroxide, where selectivity remains a key challenge. Alloying Pd with other metals and using acid and halide promoters are commonly employed to increase H2O2 selectivity; however, the sites that can selectively produce H2O2 have not been identified and the role of these additives remains unclear. Here, we report the synthesis of atomically dispersed PdClx/C as a model catalyst for H2O2 production without the presence of extended Pd surfaces. We show that these isolated cationic Pd sites can form H2O2 with significantly higher selectivity than metallic Pd nanoparticles in both the reaction of H2 and O2 and the electrochemical oxygen reduction reaction. These results demonstrate that catalysts containing high populations of isolated Pd sites are selective catalysts for this two-electron reduction reaction and that the performance of materials in the direct synthesis reaction and electrocatalytic oxygen reduction reaction has many similarities.

Oxygen reduction reaction (ORR) is greatly affected by the morphology as well as the elemental composition of the nitrogen-doped carbon-based electrocatalysts. Thus, this work focuses on: (i) nitrogen doping of different graphene-based materials (two-dimensional materials: chemically converted graphene, graphene oxide, and commercially available graphene, and one-dimensional material: graphene nanoribbons) that differ from each other by morphology as well as elemental composition and (ii) studying the ORR performance of these N-doped carbonaceous catalysts in alkaline medium. The nitrogen doping is achieved by low-cost synthetic method based on hydrothermal treatment at mild conditions. The results indicate that: (i) nitrogen doping is dependent on the carbonaceous substrate used and (ii) these N-doped graphene-based catalysts vary drastically by the electrocatalytic activity for ORR as well as the selectivity for HO2− and OH− production in alkaline medium. Roughly, predominantly HO 2 − was produced on two-dimensional graphene-based catalysts enriched with low nitrogen content (0.9–1.4 at.%) and mostly OH− was formed on graphene nanoribbons as one-dimensional catalyst containing low amount of nitrogen (2.1 at.%). This work is valuable for giving further insights into the ORR performance on N-doped graphene-based nanocarbons.

In order to enhance hydrogen peroxide (H2O2) electrogeneration, a catalyst based on less than 1 wt% of Pd nanoparticles dispersed onto commercially available Printex L6 carbon black (PCL6) is proposed and synthetized. The material was characterized by physico-chemical and electroanalytical methods, demonstrating high activity with a 320 mV lower onset potential compared to pristine PCL6 and high stability after 5000 potential cycles. Its performance places it among the most efficient bi- and monometallic electrocatalysts for H2O2 production. When testing the accumulation of H2O2, a 1.69-fold molar increase was observed for Pd1%/PCL6 compared to PCL6. Different electrochemical advanced oxidation processes based on H2O2 generation have been performed to oxidize and remove pollutants as exemplarily shown on methyl paraben in Na2SO4 solution as model pollutant. A boron-doped diamond electrode was used as anode while Pd1%/PCL6 was tested in a rotating ring disk electrode (RRDE) and gas diffusion setup. Pollutant degradation followed a pseudo-first-order reaction kinetic in the following order: anodic oxidation along with H2O2 generation (AO-H2O2)

This paper describes the synthesis and structural characterization of a novel, cheap and simple CoII complex (CoII(L)2Cl2) based on the 1,3,5-trisubstituted-pyrazoline ligand along with the electrochemical production of metal–organic electroactive films derived from this new complex. These systems were applied as electrocatalysts for hydrogen production (ACN/ACA or ACN/TFA medium) where both materials presented high performance toward hydrogen evolution. Compared to the CoII complex, the electroactive films exhibited significant electroactivity toward hydrogen evolution, presenting a remarkable TOF for H2 production (312 900 s−1, corrected by Faraday efficiency) in the presence of TFA. In addition, the generated metal–organic film showed high stability toward the electrocatalytic hydrogen production, supporting at least 1000 cycles at 20 mV s−1 in the large potential range investigated, as well as good performance and stability in the presence of 0.5 M H2SO4. Relevant insights into the mechanistic details and the role played by the CoII complex and the films during the catalytic hydrogen production are also discussed in light of the structural features and electrochemical experiments.

This short review presents a critical overview of the most recent works published in the literature related to the use of electrochemical advanced oxidation processes (EAOPs) for the treatment of antibiotics present in synthetic and real wastewaters. The first section focuses on novelties within the traditional EAOPs, including electrochemical oxidation and electrochemical Fenton-based processes. The second section is devoted to new electrochemical technologies, including heterogeneous electro-Fenton, electrochemically activated persulfate processes, and combined processes. Future perspectives about these processes are also presented to aid the continuous evolution of research in the area.

The inefficiency of conventional water treatment methods in the treatment of recalcitrant herbicides has led to the search for new, efficient and eco-friendly mechanisms for degrading these organic pollutants. Electrochemical advanced oxidation processes (EAOP) have emerged as a promising alternative due to their high degree of efficiency in degrading organic pollutants. This work investigates the removal of Tebuthiuron (TBH) in synthetic and real wastewater using different EAOPs in a flow-by reactor. The degradation/mineralization experiments were performed using boron-doped diamond electrode as anode and gas-diffusion electrode (GDE) as cathode for the in situ electrogeneration of hydrogen peroxide (H2O2). For the analysis conducted in synthetic medium, TBH degradation was found to fit well in a pseudo-first-order kinetic reaction with increasing k1 values according to the following order of efficiency: anodic oxidation (AO, 3.1 × 10−5 s−1)