Heterogeneous Electro-Fenton-like Designs for the Disposal of 2-Phenylphenol from Water

The hunt for efficient and environmentally friendly degradation processes has positioned the heterogeneous advanced oxidation processes as an alternative more interesting and economical rather than homogenous processes. Hence, the current study lies in investigating the efficiency of different heterogeneous catalysts using transition metals in order to prevent the generation of iron sludge and to extend the catalogue of possible catalysts to be used in advanced oxidation processes. In this study, nickel and zinc were tested and the ability for radical-generation degradation capacity of both ions as homogeneous was evaluated in the electro-Fenton-like degradation of 2-phenylphenol. In both cases, the degradation profiles followed a first-order kinetic model with the highest degradation rate for nickel (1 mM) with 2-phenylphenol removal level of 90.12% and a total organic reduction near 70% in 2 h. To synthesise the heterogeneous nickel catalyst, this transition metal was fixed on perlite by hydrothermal treatment and in a biochar or carbon nanofibers by adsorption. From the removal results using the three synthesized catalysts, it is concluded that the best catalysts were obtained by inclusion of nickel on biochar or nanofibers achieving in both with removal around 80% before 1 h. Thus, to synthetize a nickel electrocatalyst, nickel doped nanofibers were included on carbon felt. To do this, the amount of carbon black, nickel nanofibers and polytetrafluoroethylene to add on the carbon felt was optimized by Taguchi design. The obtained results revealed that under the optimised conditions, a near-complete removal was achieved after 2 h with high stability of the nickel electrocatalyst that open the applicability of this heterogeneous system to operate in flow systems.

Fabrication of YSZ-Carbon Felt Composite Materials by Spark Plasma Sintering Process

Dual-phase membrane composed of oxide ion conductor and electron conductor was fabricated for application to oxygen separation membranes. 8 mol% yttria-stabilized zirconia (8YSZ) and carbon felt were used for the oxide ion conducting phase and the electron conductiing phase, respectively. Carbon felt was impregnated with YSZ aqueous suspension (40 wt%), dried, then sintered by a spark plasma sintering (SPS) process under the applied pressure of 80 MPa at 1200, 1400 and 1600 ° C for 10 min. When sintered at 1600 ° C, the XRD pattern showed small peaks indicating the formation of the zirconium carbide phase, but the microstructure observed by SEM showed that the YSZ was well densified and tightly bonded with carbon felt. This method has been demonstrated to be an effective process for the fabrication of YSZ-Carbon composites with both phases percolation structure.

Ni–Fe phosphide deposited carbon felt as free-standing bifunctional catalyst electrode for urea electrolysis

A free-standing catalyst electrode for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) in a urea electrolysis cell was synthesized by electroplating a Ni–Fe alloy onto carbon felt, followed by phosphidation (P-NiFe@CF). The prepared P-NiFe@CF catalyst consisted of Ni5P4, NiP2, and FeP with 3D flower-like P-NiFe architecture on CF. P-NiFe@CF exhibited excellent electrocatalytic activity for the UOR (demanding only 1.39 V (vs. RHE) to achieve 200 mA cm−2), and for the HER with a low overpotential of 0.023 V (vs. RHE) at 10 mA cm−2, indicating its feasibility as a bifunctional catalyst electrode for urea electrolysis. A urea electrolysis cell with P-NiFe@CF as both the free-standing anode and cathode generated a current density of 10 mA cm−2 at a cell potential of 1.37 V (vs. RHE), which is considerably lower than that of water electrolysis, and also lower than previously reported values. The results indicate that the P-NiFe@CF catalyst electrodes can be used as free-standing bifunctional electrodes for urea electrolyzers.

A high-performance ammonia plasma-treated WO3@carbon felt electrode for vanadium redox flow batteries

Due to the pressing need for harnessing renewable energy, sizable energy storage technologies have become increasingly critical, among which vanadium redox flow batteries (VRFBs) are considered as one of the promising technologies. However, the lack of high-performance electrodes hinders the development of VRFBs. Herein, we report a new ammonia plasma-treated WO3@carbon felt as a high-performance electrode for VRFBs. The ammonia plasma introduces not only N-contained functional groups but also oxygen deficiencies on WO3, which provide additional active sites and improve the conductivity, leading to high catalysis for both cathodic and anodic vanadium redoxes. As a result, the energy efficiency and the power density of the VRFB increase from 78.9% to 86% and from 365.5 mWcm[Formula: see text] to 389.6 mWcm[Formula: see text], respectively. Moreover, the energy efficiency of composite electrodes remains stable for more than 300 cycles. This study provides a new strategy for designing cost-effective, environmentally friendly, and high-performance electrodes for future VRFBs.

Combined Electro-Fenton and Anodic Oxidation Processes at a Sub-Stoichiometric Titanium Oxide (Ti4O7) Ceramic Electrode for the Degradation of Tetracycline in Water

The mineralization of tetracycline by electrochemical advanced oxidation processes (EAOPs) as well as the study of the toxicity of its intermediates and degradation products are presented. Electro-Fenton (EF), anodic oxidation (AO), and electro-Fenton coupled with anodic oxidation (EF/AO) were used to degrade tetracycline on carbon felt (cathode) and a sub-stoichiometric titanium oxide (Ti4O7) layer deposited on Ti (anode). As compared to EF and AO, the coupled EF/AO system resulted in the highest pollutant removal efficiencies: total organic carbon removal was 69 ± 1% and 68 ± 1%, at 20 ppm and 50 ppm of initial concentration of tetracycline, respectively. The effect of electrolysis current on removal efficiency, mineralization current efficiency, energy consumption, and solution toxicity of tetracycline mineralization were investigated for 20 ppm and 50 ppm tetracycline. The EF/AO process using a Ti4O7 anode and CF cathode provides low energy and high removal efficiency of tetracycline caused by the production of hydroxyl radicals both at the surface of the non-active Ti4O7 electrode and in solution by the electro-Fenton process at the cathodic carbon felt. Complete removal of tetracycline was observed from HPLC data after 30 min at optimized conditions of 120 mA and 210 mA for 20 ppm and 50 ppm tetracycline concentrations. Degradation products were elucidated, and the toxicity of the products were measured with luminescence using Microtox® bacteria toxicity test.