Tuning Task-Specific Ionic Liquids for the Extractive Desulfurization of Liquid Fuel

Extractive desulfurization of liquid fuel is a simple process that requires minimum energy input and can be operated via existing liquid–liquid extraction apparatuses. In particular, to achieve deep desulfurization, the conventional hydrodesulfurization (HDS) process has shown limitations in the removal of aromatic sulfur compounds. Recently, extractive desulfurization using a new type of nonvolatile solvent, ionic liquids (ILs), has yielded promising results. However, there is a lack of systematic evaluation of the effect of IL structure on desulfurization efficiency, and a lack of mechanistic understanding regarding how ILs lead to the partition of aromatic sulfur compounds from fuel to the IL phase. The present study examines a total of 71 ILs and two deep eutectic solvents (DESs) with combinations representing various cations and anions. We identify a number of ILs that yield high partition coefficients [up to 1.85 mg­(S) kg (IL)⁻¹/mg­(S) kg (oil)⁻¹] for the partition of aromatic sulfur compounds between ILs and <i>n</i>-octane or <i>n</i>-dodecane as surrogates for gasoline or diesel, respectively. We find that the high sulfur partition coefficient correlates with a high dipolarity/polarizability (π*) or a low solvent polarizability (SP) of ILs carrying the same cation and different anions, but correlates with a low dipolarity/polarizability (π*) for ILs carrying the same anion paired to cations bearing different alkyl chain lengths. We further demonstrate that a four-step extraction using ILs can achieve 99% dibenzothiophene (DBT) removal (i.e., an initial sulfur content of 500 ppm is reduced to <5 ppm following extraction)

Ionic Liquid-Assisted Synthesis of Nanoscale (MoS₂)_<i>x</i>(SnO₂)_1–<i>x</i> on Reduced Graphene Oxide for the Electrocatalytic Hydrogen Evolution Reaction

Layered transition metal dichalcogenides (TMDs) have attracted increased attention due to their enhanced hydrogen evolution reaction (HER) performance. More specifically, ternary TMD nanohybrids, such as MoS_{2(1–<i>x</i>)}Se_2<i>x</i> or bimetallic sulfides, have arisen as promising electrocatalysts compared to MoS₂ and MoSe₂ due to their electronic, morphologic, and size tunabilities. Herein, we report the successful synthesis of few-layered MoS₂/rGO, SnS₂/rGO, and (MoS₂)_<i>x</i>(SnO₂)_1–<i>x</i>/rGO nanohybrids anchored on reduced graphene oxide (rGO) through a facile hydrothermal reaction in the presence of ionic liquids as stabilizing, delayering agents. Spectroscopic and microscopic techniques (electron microscopy, X-ray diffraction, Raman spectroscopy, neutron activation analysis, and UV–vis spectrophotometry) are used to validate the hierarchical properties, phase identity, and the smooth compositional tunability of the (MoS₂)_<i>x</i>(SnO₂)_1–<i>x</i>/rGO nanohybrids. Linear sweep voltammetry measurements reveal that incorporation of Sn into the ternary nanohybrids (as a discrete SnO₂ phase) greatly reduces the overpotential by 90–130 mV relative to the MoS₂ electrocatalyst. Significantly, the (MoS₂)_0.6(SnO₂)_0.4/rGO nanohybrid displays superior catalytic performance over MoS₂ alone, exhibiting a low overpotential (η₁₀) of 263 ± 5 mV and a small Tafel slope of 50.8 mV dec^–1. The hybrid catalyst shows high stability for the HER in acidic solutions, with negligible activity loss after 1000 cycles. The hierarchical structures and large surface areas possessing exposed, active edge sites make few-layered (MoS₂)_<i>x</i>(SnO₂)_1–<i>x</i>/rGO nanohybrids promising nonprecious metal electrocatalysts for the HER