Recent Publications Feed (ADMIN)

Acetic acid is an important organic solvent for the chemical industry, such as in catalytic hydrogenation and for electrosynthesis reactions generally. In this work, the adsorption and electrochemical oxidation of several sulfur‐containing anions (S2−, S2O42−, S2O52− and SO32−) over Pt electrodes in a mixture of sulfuric acid/acetic acid was investigated by using cyclic voltammetry. Electrochemical oxidation provides a means of regenerating Pt catalysts and the sulfur‐containing anions studied are examples of species that might be produced under synthetic conditions or could be present as impurities in industrial feedstock. To determine the oxidation reaction mechanism and its surface‐structure sensitivity, Pt polycrystalline and single‐crystal electrodes are implemented in this study. It is found that the oxidation of the sulfur‐containing species on Pt polycrystalline electrode takes place at higher potentials in comparison to the same reactions in aqueous media. This is attributed to the low coverage of surface oxide, owing to the low concentration of water and the adsorption of acetate at the surface. Experiments on the Pt basal planes and stepped surfaces reveal a strong surface‐structure dependence for the oxidation of all the sulfur‐containing species. These results provide valuable information that will aid the engineering of nanocatalysts with specific crystalline structure less prone to contamination during catalytic process in mixtures of sulfuric/acetic acid.

Understanding the poisoning and recovery of precious metal catalysts is greatly relevant for the chemical industry dealing with the synthesis of organic compounds. For example, hydrogenation reactions typically use platinum catalysts and sulfuric acid media, leading to poisoning by sulfur-containing species. In this work, we have applied electrochemical methods to understand the status and recovery of Pt catalysts by studying the electro-oxidation of a family of sulfur-containing species adsorbed at several types of Pt electrodes: (i) polycrystalline Pt foil; (ii) Pt single-crystal electrodes; and (iii) Pt nanoparticles supported on Vulcan carbon. The results obtained from polycrystalline Pt electrodes and Pt nanoparticles supported on Vulcan carbon demonstrate that all sulfur-containing species with different oxidation states (2−, 3+ and 4+) lead to the poisoning of active sites on the Pt surface. X-ray photoelectron spectroscopy (XPS) analysis was employed to elucidate the chemical state of sulfur species during the recovery process. The degree of poisoning decreased with increased sulfur oxidation state, while the rate of regeneration of the Pt surfaces generally increases with the oxidation state of the sulfur species. Finally, the use of Pt single-crystal electrodes reveals the surface-structure sensitivity of the oxidation of the sulfur species. This information could be useful in designing catalysts that are less susceptible to poisoning and/or more easily regenerated. These studies demonstrate voltammetry to be a powerful method for assessing the status of platinum surfaces and for recovering catalyst activity, such that electrochemical methods could find applications as sensors in catalysis and for catalyst recovery in situ.

Boron doped diamond (BDD) is continuing to find numerous electrochemical applications across a diverse range of fields due to its unique properties, such as having a wide solvent window, low capacitance, and reduced resistance to fouling and mechanical robustness. In this review, we showcase the latest developments in the BDD electrochemical field. These are driven by a greater understanding of the relationship between material (surface) properties, required electrochemical performance, and improvements in synthetic growth/fabrication procedures, including material postprocessing. This has resulted in the production of BDD structures with the required function and geometry for the application of interest, making BDD a truly designer material. Current research areas range from in vivo bioelectrochemistry and neuronal/retinal stimulation to improved electroanalysis, advanced oxidation processes, supercapacitors, and the development of hybrid electrochemical-spectroscopic- and temperature-based technology aimed at enhancing electrochemical performance and understanding.