Sustainable Energy & Fuels最新文献

This study applied the lattice expansion strategy to enhance the performance of the CuMn₂O₄ oxygen carrier. The lattice-expanded oxygen carrier was developed using sulfurization and re-oxidation processes. The lattice of re-oxidized CuMn₂O₄ (CuMn₂O_3.5S_0.5) did not shrink to the original lattice and maintained the expanded structure because of the residual sulfur in the CuMn₂O₄. Density functional theory calculations predicted that the lattice expansion accelerates the CH₄ oxidation kinetics on the surface and the oxygen mobility in the oxygen carrier. As a result, the oxygen transfer rate was expected to be accelerated. Experimental analysis confirmed the predicted enhancement. The comprehensive characteristic analysis revealed notable variations in the lattice structure and oxidation state between lattice-expanded CuMn₂O₄ and pristine CuMn₂O₄ because of the enhanced oxygen transfer rate, as confirmed by temperature-programmed analysis. The chemical looping combustion test showed that the oxygen transfer rate of lattice-expanded CuMn₂O₄ was 1.6 times higher than that of pristine CuMn₂O₄. The simulation predicted an enhanced oxygen transfer rate of the oxygen carrier. Based on the results, the strategy of lattice expansion could be a universal approach to enhance the oxygen transfer rate and improve the overall performance of the oxygen carrier.

Molybdenum carbide is deemed a potential electrode material for the hydrogen evolution reaction (HER) under different pH condition electrolytes because of its unique metal-like electronic structure. Herein, we report a series of molybdenum carbide-based catalytic electrodes that were prepared by adjusting the proportion of glucose and ammonium molybdate in the molten salt. The prepared electrocatalysts mainly include Mo₂C, Mo₂C/C and Mo₂C/MoO₂. The composition influences electronic structure and microstructure of Mo₂C, impacting the HER performance. As for Mo₂C/C, because of the regulation of the carbon substrate, the charge transfer efficiency and electronic structure were improved. It exhibits satisfactory HER performance with low overpotentials at 10 mA cm⁻² in alkaline (280 mV) and acidic electrolytes (264 mV). Meanwhile, it presents good Tafel slopes of 102 mV dec⁻¹ (alkaline) and 88 mV dec⁻¹ (acidic). The outstanding HER performance can be ascribed to the full exposure of the active sites and a strong in situ coupling between the carbon matrix and the nanoscale Mo₂C. The carbon matrix not only offers abundant nucleation sites that prevent agglomeration of the Mo₂C nanosheets, but also exhibits charge transfer towards Mo₂C. This synthesis strategy may provide an idea for preparing transition metal carbide-based composite materials to apply in energy fields.

Electrochemical cells with fluorine-based polymer electrolyte membranes (PEMs) and Ru catalysts have been investigated for the production of methane (CH₄) from CO₂ and H₂O by using electricity at 120 °C. CH₄ was synthesized with a rate of 12 nmol s⁻¹ cm⁻² at a current density of 10 mA cm⁻² with a CO₂ flow of 0.055 ml_STP min⁻¹ in the cathode vessel and with an Ar + H₂O flow of 10 ml_STP min⁻¹ + 10 μL_liquid min⁻¹ in the anode vessel (STP; standard temperature and pressure at 0 °C and 101.3 kPa, respectively). This rate was corresponding to the current efficiency of ca. 85%, and unreacted H₂ and subproducts of CO were obtained with current efficiencies of ca. 14 and 1%, respectively. The properties of temperature and current density dependence were discussed in this article. The present system exhibits significantly higher selectivity in synthesizing CH₄ compared to electrochemical CO₂ reduction systems at the electrode/electrolyte interfaces. Electrochemical CO₂ reduction did not take place in the present system, and the importance of the combination of water electrolysis and catalytic methanation at solid/gas interfaces was proposed. A comparative study between phosphate (CsH₂PO₄/SiP₂O₇) at 250 °C and polymer electrolytes at 120 °C was performed and the possibility for practical applications of both systems was discussed.

There is a high requirement for very efficient catalytically active materials to produce and store sustainable fuels to fulfill global energy demand, and the design of cost-effective multifunctional electrocatalysts for the oxygen evolution reaction (OER) and supercapacitors has become prominent. Herein, quaternary chalcogenides of Cu₂NiBiS₄ and Cu₂NiBiSe₄ have been fabricated by a facile solvothermal method and applied for electrocatalytic OER and supercapacitance performance. Material characterization was undertaken with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), and UV-visible spectroscopy. The Cu₂NiBiSe₄ catalyst shows a low overpotential of 175 at 10 mA cm⁻² current density and a low Tafel slope of 61 mV dec⁻¹ for the OER. Whereas the Cu₂NiBiS₄ electrocatalyst retains an overpotential of 212 mV and Tafel slope of 78 mV dec⁻¹ for the OER at 10 mA cm⁻². A long-term durability test of Cu₂NiBiSe₄ for 12 h at 10 mA cm⁻² current density suggests that it may be a suitable substitute for noble-metal-based electrocatalysts for the oxidation of water in alkaline media. Moreover, Cu₂NiBiSe₄ delivers boosted supercapacitive behavior with an exceptional specific capacity of 1443 F g⁻¹ at 2.5 A g⁻¹ compared to Cu₂NiBiS₄ (1221 F g⁻¹ at 2.5 A g⁻¹). Furthermore, Cu₂NiBiSe₄ exhibits an admirable energy density of 24.3 W h kg⁻¹ at a power density of 450.7 W kg⁻¹ together with 98% retention after 100 cycles.

Correction for ‘A review on thermochemical based biorefinery catalyst development progress’ by Mortaza Gholizadeh et al., Sustainable Energy Fuels, 2023, 7, 4758–4804, https://doi.org/10.1039/D3SE00496A.

Given the interest in solar fuels production through electron transfer from the conduction band of semiconductor electrodes to reduce CO₂ or produce H₂, a theoretical and experimental examination has been made of these electrodes under an accumulation bias. This has been done with the use of a general model from the solid state physics literature that encompasses degeneracy situations in the electrode, a scope that is greater than the present model in use that assumes all donors are fully ionized. In an illustration of the aspects of these two models, experimental capacitance measurements with p-Si, n-Si, and n-InP have been made with a TBAPF₆ electrolyte in acetonitrile. A variation of the TBAPF₆ concentration under 0.50 M at the Si semiconductor electrode was used to control the capacitance of the Helmholtz layer and revealed that moderately doped semiconductors can only be biased −200 mV into accumulation before the applied potential induces band edge shifts with respect to a reference electrode. At degenerate n-InP electrodes, this shift begins at a lower potential negative of a flatband condition. The fully ionized model was found to fail with increasing bias in the accumulation region. The general model also describes expected behavior for the inversion region of these electrodes and the implications of its predictions in this regime are discussed.

Acid-catalysed alcoholysis of lignocellulosic biomass produces a tailorable advanced biofuel blend, with the primary products being an alkyl levulinate, a dialkyl ether, and alcohol. Varying process parameters during production has the potential to produce differing quantities of the three components, affecting both physical and combustion properties. Starting alcohols, ethanol, n-butanol, and n-pentanol were chosen to investigate the effects of carbon chain length on the physical properties of model ethyl, butyl, and pentyl-based blends, produced from alcoholysis. Blends were designed to contain ≥50 vol% alkyl levulinate, with the remainder composed of the corresponding ether and alcohol. Existing fuel standards set limits for different physical and chemical properties that should be met to enhance commercial viability. In the present work, the flash point, density at 15 °C and kinematic viscosity at 40 °C (KV40) were measured for a range of three-component blends. The study also investigated the impact of diesel (EN 590 compliant) blending on these properties, at 0–95% volume diesel. A design of experiments approach selected optimal blends for testing and was used to develop predictive physical properties models based on polynomial fits. The predictive models for the properties of the three-component blends had average absolute relative deviations <5%, indicating their utility for predicting generalised blend properties. The models facilitated the determination of blend boundaries, within which the formulations would meet existing fuel standards limits. Flash points ranged from 26–57 °C and 54–81 °C for the butyl and pentyl-based blends without diesel, respectively. Densities at 15 °C ranged between 0.879–0.989 g cm⁻³, 0.874–0.957 g cm⁻³, and 0.878–0.949 g cm⁻³ for the ethyl, butyl and pentyl-based blends without diesel, respectively. The KV40 ranged from 1.186–1.846 mm² s⁻¹ and 1.578–2.180 mm² s⁻¹ for butyl and pentyl-based blends without diesel, respectively. Butyl-based blends with diesel were found to be the most practically suitable and met the BS 2869 density limits.

Conversion of organosolv lignins isolated with and without an inorganic acid catalyst (H₂SO₄) from hard- and softwood (birch and spruce) into bio-oil through hydrothermal liquefaction has been investigated. Furthermore, fractions of the isolated bio-oils were catalytically deoxygenated to improve the bio-oil properties. As elucidated through NMR, both biomass source and extraction mode influence the bio-oil product distribution. Depending on whether the lignins carry a high content of native structures, or are depolymerized and subsequently condensed in the presence of sugar dehydration products, will dictate heavy oil (HO) and light oil (LO) distribution, and skew the HO product composition, which again will influence the requirements upon catalytical deoxygenation.

Developing bifunctional catalysts with low reversible oxygen reaction potentials (ΔE) to improve the energy conversion efficiency and cycling stability of rechargeable zinc–air batteries (ZABs) remains a huge challenge. Herein, a series of catalysts containing a hollow N-doped carbon cage with FeCo alloy nanoparticles encapsulated (Fe_xCo_y@N-C) are fabricated by a strategy of epitaxial growth followed by pyrolysis. Thereinto, owing to the relative balance and optimal synergy between the active sites of the FeCo alloy and the specific surface area of porous carbon, the Fe_xCo_y@N-C-0.3 catalyst displays a best electrocatalytic performance in both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a small ΔE value of 0.686 V. Aqueous ZABs catalyzed by Fe_xCo_y@N-C-0.3 exhibit a high peak power density of 191 mW cm⁻² and the voltage gap only increased by about 30 mV after 345 h. Conspicuously, the aqueous ZABs still maintain an extremely small charge–discharge voltage gap of 0.73 V after 345 h, which is better than the performance of ZABs based on metal catalysts reported in many studies. Moreover, flexible ZABs based on the Fe_xCo_y@N-C-0.3 catalyst demonstrate an excellent cycling stability of 50 h and outstanding mechanical stability under different bending states.

Pinane is a product derived from turpentine, a renewable resource that is highly valued. Due to its unique multicyclic ring structure, pinane has a relatively high energy density of 35.6 MJ L⁻¹, making it an excellent potential alternative to jet fuel. In this work, the low-temperature oxidation of pinane is comprehensively studied concerning the oxidative stability requirement of jet fuels. The apparent activation energy E_a and pre-exponential factor A of pinane oxidation are acquired according to the Kissinger method using a P-DSC apparatus as 97.6 ± 2.7 kJ mol⁻¹ and 5.3 ± 3.7 × 10¹⁰ min⁻¹, respectively, rendering it a relatively more oxygen-susceptible hydrocarbon compared to non-strained hydrocarbons. DFT calculations and experimental investigations have shown that the low-temperature oxidation of pinane begins with the hydrogen atom transfer (HAT) reaction and the rupture of the strained ring. Interestingly, although pinane can be easily oxidized, it shows very low deposition propensity in the JFTOT test, qualifying it as a potential jet fuel.