Modifying the Electrocatalytic Selectivity of Oxidation Reactions with Ionic Liquids

Highly efficient removal of diclofenac sodium with polystyrene supported ionic liquid

ABSTRACTDiclofenac sodium (DS) is now recognized as an emerging pollutant, and is one of the most commonly discovered pharmaceuticals in water due to its extensive application in the clinic. This study examined the adsorption performance of a polystyrene-supported ionic liquid material (PS-[Nim][Cl]) for the removal of diclofenac sodium (DS) from water. The data from this study showed that maximum removal of DS can be achieved even in conditions with significant pH and temperature fluctuations. The adsorption process was rapid, more than 90% of DS could be removed within the first 10 min and adsorption equilibrium could be reached in just 30 min with a high removal efficiency (>99.9%). Adsorption reached saturation with a maximum adsorption capacity of approximately 785.2 mg/g. Moreover, the presence of K+, Na+, Ca2+, Mg2+, Cl-, and H2PO4- ions had little influence on DS adsorption, even when concentrations of these ions were 10,000 times higher than that of DS in water samples. The adsorbent also showed promising performance for the treatment of environmental water samples and groundwater containing DS.

Toward High-Energy-Density Fuels for Direct Liquid Organic Hydrogen Carrier Fuel Cells: Electrooxidation of 1-Cyclohexylethanol

Electrochemically active liquid organic hydrogen carriers (EC-LOHCs) can be used directly in fuel cells; so far, however, they have rather low hydrogen storage capacities. In this work, we study the electrooxidation of a potential EC-LOHC with increased energy density, 1-cyclohexylethanol, which consists of two storage functionalities (a secondary alcohol and a cyclohexyl group). We investigated the product spectrum on low-index Pt single-crystal surfaces in an acidic environment by combining cyclic voltammetry, chronoamperometry, and in situ infrared spectroscopy, supported by density functional theory. We show that the electrooxidation of 1-cyclohexylethanol is a highly structure-sensitive reaction with activities Pt(111) ≫ Pt(100) > Pt(110). Most importantly, we demonstrate that 1-cyclohexylethanol can be directly converted to acetophenone, which desorbs from the electrode surface. However, decomposition products are formed, which lead to poisoning. If the latter side reactions could be suppressed, the electrooxidation of 1-cyclohexylethanol would enable the development of EC-LOHCs with greatly increased hydrogen storage capacities.

Chemical and Structural In-Situ Characterization of Model Electrocatalysts by Combined Infrared Spectroscopy and Surface X-ray Diffraction

New diagnostic approaches are needed to drive progress in the field of electrocatalysis and address the challenges of developing electrocatalytic materials with superior activity, selectivity, and stability. To this end, we developed a versatile experimental setup that combines two complementary in-situ techniques for the simultaneous chemical and structural analysis of planar electrodes under electrochemical conditions: high-energy surface X-ray diffraction (HE-SXRD) and infrared reflection absorption spectroscopy (IRRAS). We tested the potential of the experimental setup by performing a model study in which we investigated the oxidation of preadsorbed CO on a Pt(111) surface as well as the oxidation of the Pt(111) electrode itself. In a single experiment, we were able to identify the adsorbates, their potential dependent adsorption geometries, the effect of the adsorbates on the surface morphology, and the structural evolution of Pt(111) during surface electro-oxidation. In a broader perspective, the combined setup has a high application potential in the field of energy conversion and storage.

Ligand Hybridization for Electro-reforming Waste Glycerol into Isolable Oxalate and Hydrogen

The electro-reforming of glycerol is an emerging technology of simultaneous hydrogen production and biomass valorization. However, its complex reaction network and limited catalyst tunability restrict the precise steering toward high selectivity. Herein, we incorporated the chelating phenanthrolines into the bulk nickel hydroxide and tuned the electronic properties by installing functional groups, yielding tunable selectivity toward formate (max 92.7 %) and oxalate (max 45.3 %) with almost linear correlation with the Hammett parameters. Further combinatory study of intermediate analysis and various spectroscopic techniques revealed the electronic effect of tailoring the valence band that balances between C-C cleavage and oxidation through the key glycolaldehyde intermediate. A two-electrode electro-reforming setup using the 5-nitro-1,10-phenanthroline-nickel hydroxide catalyst was further established to convert crude glycerol into pure H₂ and isolable sodium oxalate with high efficiency.