Rudimentary simple, single step fabrication of nano-flakes like AgCd alloy electro-catalyst for oxygen reduction reaction in alkaline fuel cell

Biochar-loaded iron oxide as a novel electrode for the electro-Fenton degradation of sulfaquinoxaline: Performance evaluation, mechanistic insights, and toxicity transformation

In this work, carboxymethyl cellulose (CMC)-modified biochar (BC)-supported Fe3O4 was prepared for the degradation of sulfaquinoxaline (SQX) in a heterogeneous electro-Fenton process. The degradation rate of 10 mg/L SQX reached 94.2 % after 180 min of Fe3O4(CMC)/BC treatment, compared to 61.2 % with Fe3O4/BC. CMC allowed Fe3O4 particles to be more evenly distributed on the biochar surface, and its electron transfer capacity effectively activated the in situ generated H2O2 on the electrode with a maximum H2O2 yield of 17.9 mg/L. The produced 1O2 and ⋅O2- are the primary contributors to SQX degradation. The aniline of SQX is susceptible to electrophilic attack, whereas quinoxaline is susceptible to free radical attack, with bis-methylation, heterocyclic oxidation, and amino oxidation being the major reactions in the decomposition of SQX. Toxicity assessment by ECOSAR and T.E.S.T. modeling showed that all the intermediates were considerably less biotoxic than the parent compound. Density functional theory calculations showed that the O2 adsorption and H2O2 decomposition processes are spontaneous reactions, and the intermediates absorbed on the Fe atom have an increased energy potential and a tendency to be less active. The results of material cycling tests and metal ion leaching experiments confirmed the good reusability of the prepared cathode. Additionally, Fe3O4(CMC)/BC achieved excellent performance in livestock wastewater (SQX removal of 93.4 % and COD removal of 79.9 %), demonstrating the possibility of practical application. This study offers a theoretical foundation for the use of novel composite cathode materials to degrade persistent pollutants.

n-Type Cu2O/α-Fe2O3 Heterojunctions by Electrochemical Deposition: Tuning of Cu2O Thickness for Maximum Photoelectrochemical Performance

Here, we report the enhanced photoelectrochemical performance of surface modified hematite thin films with n-type copper oxide nanostructures (Cu2O/Fe2O3) obtained through simple electrochemical deposition method. The thickness and amount of cuprous oxide layer were varied by simply changing the number of electrodeposition cycles (viz. 5, 10, 25, 50 and 100) in order to understand its thermodynamic and kinetic influence on the photoelectrochemical activity of the resultant nano-heterostructures. Structural and morphological characteristics of the obtained Cu2O/Fe2O3 films have been studied by absorption spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analysis. Electrochemical investigations such as linear sweep voltammetry, Mott–Schottky analysis, and electrochemical impedance spectroscopy suggested the formation of n-type Cu2O layers over the hematite films with varying charge-carrier densities, ranging from 0.56×1019 to 3.94×1019 cm−3, that varies with the number of cycles of electrochemical deposition. Besides, the thickness of deposited cuprous oxide layer is noted to alter the net electrochemical and photo-electrochemical response of the base material. An interesting, peak event was recorded for a particular thickness of the cuprous oxide layer (obtained after 25 cycles of electrochemical deposition) below and above which the efficiency of catalyst was impaired. The heterojunction obtained thus, followed well known Z-scheme and gave appreciable increment in the photocurrent response.

Silver@Nitrogen-Doped Carbon Nanorods as a Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction in Alkaline Media

In recent years, various platinum-free catalysts for the oxygen reduction reaction (ORR) have attracted great attention due to the limited natural abundance and high cost of platinum. Herein, Ag@N-C (N-C: nitrogen-doped carbon) nanorods for the ORR were synthesized through chemical polymerization and pyrolysis methods by using pyrrole and silver nitrate as raw materials. Pyrolysis could significantly increase the specific surface area of as-synthesized catalysts and convert pyrrolic-N into graphitic-N and pyridinic-N. The results of electrochemical tests show that the Ag@N-C-900 catalyst (pyrolyzed at 900 °C) exhibits highly efficient ORR catalytic activity, improved stability, and better methanol resistance in comparison to that of Pt/C catalyst in alkaline media.