Stability Testing of Pt x Sn1 − x /C Anodic Catalyst for Renewable Hydrogen Production Via Electrochemical Reforming of Ethanol

An Alkaline-Acid Glycerol Electrochemical Reformer for Simultaneous Production of Hydrogen and Electricity

This study shows the results, for the first time, of an glycerol alkaline-acid electrolyzer. Such a configuration allows spontaneous operation, producing energy and hydrogen simultaneously as a result of the utilization of the neutralization and fuel chemical energy. The electroreformer—built with a 20 wt% Pd/C anode and cathode, and a Na⁺-pretreated Nafion^® 117—can simultaneously produce hydrogen and electricity in the low current density region, whereas it operates in electrolysis mode at high current densities. In the spontaneous region, the maximum power densities range from 1.23 mW cm⁻² at 30 °C to 11.9 mW cm⁻² at 90 °C, with a concomitant H₂ flux ranging from 0.0545 STP m⁻³ m⁻² h⁻¹ at 30 °C to 0.201 STP m⁻³ m⁻² h⁻¹ at 90 °C, due to the beneficial effect of the temperature on the performance. Furthermore, over a chronoamperometric test, the electroreformer shows a stable performance over 12 h. As a challenge, proton crossover from the cathode to the anode through the cation exchange Nafion^® partially reduces the pH gradient, responsible for the extra electromotive force, thus requiring a less permeable membrane.

Photoelectric properties of aromatic triangular tri-palladium complexes and their catalytic applications in the Suzuki-Miyaura coupling reaction

The photoelectric properties and catalytic activities of substituted triphenylphosphine and sulfur/selenium ligand supported aromatic triangular tri-palladium complexes 1-4, abbreviated as [Pd₃]⁺, were investigated. The cyclic voltammogram of [Pd₃]⁺ in CH₃CN-ⁿBu₄NPF₆ showed a single quasi-reversible wave which was consistent with their robust property and provided preliminary proof for their electron transfer processes in catalysis. With excitation at 267 nm, [Pd₃]⁺ exhibited strong ratiometric fluorescence at 550 and 780 nm at a temperature gradient from 77 K to 287 K. These peculiar triangular tri-palladium complexes showed excellent catalytic activities and exclusive reactivity with aryl iodides over the other halogenated aromatics in the Suzuki-Miyaura coupling reaction. The electronic and steric hindrance effects of substituents on the aryl iodides and aryl boronic acids including heteroaromatics like pyridine, pyrazine and thiophenes were explored and most substrates achieved up to 99% of yields. (2-[1,1'-Biphenyl]-2-ylbenzothiazole) which was analogous to the selective cyclooxygenase-2 (COX-2) inhibitors was also synthesized with our tri-palladium catalyst and gave good isolated yield (94%). The study of the catalytic process revealed that the mechanism of the reaction may involve the replacement of the sulphur ligand on [Pd₃]⁺ by iodine from aryl iodides, which was beneficial for the matching of C-I bond energy.

Membrane-Less Ethanol Electrooxidation over Pd-M (M: Sn, Mo and Re) Bimetallic Catalysts

The effect of the addition of three oxophilic co-metals (Sn, Mo and Re) on the electrochemical performance of Pd in the ethanol oxidation reaction (EOR) was investigated by performing half-cell and membrane-less electrolysis cell experiments. While the additions of Sn and Re were found to improve significantly the EOR performance of Pd, Mo produced no significant promotional effect. When added in significant amounts (50:50 ratio), Sn and Re produced a 3–4 fold increase in the mass-normalized oxidation peak current as compared to the monometallic Pd/C material. Both the electrochemical surface area and the onset potential also improved upon addition of Sn and Re, although this effect was more evident for Sn. Cyclic voltammetry (CV) measurements revealed a higher ability of Sn for accommodating OH- species as compared to Re, which could explain these results. Additional tests were carried out in a membrane-less electrolysis system. Pd50Re50/C and Pd50Sn50/C both showed higher activity than Pd/C in this system. Chronopotentiometric measurements at constant current were carried out to test the stability of both catalysts in the absence of a membrane. Pd50Sn50/C was significantly more stable than Pd50Re50/C, which showed a rapid increase in the potential with time. Despite operating in the absence of a membrane, both catalysts generated a high-purity (e.g., 99.99%) hydrogen stream at high intensities and low voltages. These conditions could lead to significant energy consumption savings compared to commercial water electrolyzers.

A Discussion on the Unique Features of Electrochemical Promotion of Catalysis (EPOC): Are We in the Right Path Towards Commercial Implementation?

The phenomenon of “Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA)” or “Electrochemical Promotion of Catalysis (EPOC)” has been extensively studied for the last decades. Its main strength, with respect to conventionally promoted catalytic systems, is its capability to modify in-situ the activity and/or selectivity of a catalyst by controlling the supply and removal of promoters upon electrical polarization. Previous reviews have summarized the main achievements in this field from both the scientific and technological points of view. However, to this date no commercial application of the EPOC phenomenon has been developed, although numerous advances have been made on the application of EPOC on catalyst nanostructures (closer to those employed in conventional catalytic systems), and on the development of scaled-up reactors suitable for EPOC application. The main bottleneck for EPOC commercialization is likely the choice of the right chemical process. Therefore, from our point of view, future efforts should focus on coupling the latest EPOC advances with the chemical processes where the EPOC phenomenon offers a competitive advantage, either from an environmental, a practical or an economic point of view. In this article, we discuss some of the most promising cases published to date and suggest future improvement strategies. The considered processes are: (i) ethylene epoxidation with environmentally friendly promoters, (ii) NOx storage and reduction under constant reaction atmosphere, (iii) CH4 steam reforming with in-situ catalyst regeneration, (iv) H2 production, storage and release under fixed temperature and pressure, and (v) EPOC-enhanced electrolysers.

Greener Routes to Biomass Waste Valorization: Lignin Transformation Through Electrocatalysis for Renewable Chemicals and Fuels Production

Lignin valorization is essential for biorefineries to produce fuels and chemicals for a sustainable future. Today's biorefineries pursue profitable value propositions for cellulose and hemicellulose; however, lignin is typically used mainly for its thermal energy value. To enhance the profit potential for biorefineries, lignin valorization would be a necessary practice. Lignin valorization is greatly advantaged when biomass carbon is retained in the fuel and chemical products and when energy quality is enhanced by electrochemical upgrading. Though lignin upgrading and valorization are very desirable in principle, many barriers involved in lignin pretreatment, extraction, and depolymerization must be overcome to unlock its full potential. This Review addresses the electrochemical transformation of various lignins with the aim of gaining a better understanding of many of the barriers that currently exist in such technologies. These studies give insight into electrochemical lignin depolymerization and upgrading to value-added commodities with the end goal of achieving a global low-carbon circular economy.

Improving photocatalytic free radical polymerization with hydrochloric acid

Improving photocatalytic free radical polymerization of vinyl acetate with hydrochloric acid.