Energy & Fuels最新文献

Electrochemical reduction of carbon monoxide offers a possible route to produce valuable chemicals (such as acetate, ethanol or ethylene) from CO₂ in two consecutive electrochemical reactions. Such deeply reduced products are formed via the transfer of 4-6 electrons per CO molecule. Assuming similar-sized CO₂ and CO electrolyzers, 2-3-times larger current densities are required in the latter case to match the molar fluxes. Such high reaction rates can be ensured by tailoring the structure of the gas diffusion electrodes. Here, the structure of the cathode catalyst layer was systematically varied using different polymeric binders to achieve high reaction rates. Simple linear polymers, bearing the same backbone but different functional groups were compared to highlight the role of different structural motifs. The comparison was also extended to simple linear, partially fluorinated polymers. Interestingly, in some cases similar results were obtained as with the current state-of-the-art binders. Using different surface-wetting characterization techniques, we show that the hydrophobicity of the catalyst layer-provided by the binder- is a prerequisite for high-rate CO electrolysis. The validity of this notion was demonstrated by performing CO electrolysis experiments at high current density (1 A cm^-2) for several hours using PVDF as the catalyst binder.

The quasi-one-dimensional environment-friendly light-harvesting material Sb₂S₃ attracts tremendous attention for photovoltaic applications due to its superior materials and optoelectronic properties. The film orientation and grain boundary are two crucial concerns that greatly influence the device performance of Sb₂S₃ solar cells. In this work, the film orientation and grain boundary of Sb₂S₃ thin films processed by vacuum-based close-spaced sublimation (CSS) and solution-based chemical bath deposition (CBD) and hydrothermal deposition (HD) methods were evaluated. Careful characterization reveals that the vacuum-based method typically affords compact Sb₂S₃ films with pronounced [hk1] orientations, while solution-based methods deliver large-grained Sb₂S₃ films with ultralow grain boundary density. The CBD- and HD-processed devices yielded power conversion efficiencies of 6.43 and 6.51%, respectively, higher than 5.81% for the CSS-processed device. This should be closely associated with the balance of the favorable [hk1] orientations for efficient charge transport and the reduced grain boundary density for suppressed carrier recombination. This work provides insight information for further enhancing the performance of Sb₂S₃ solar cells by devoting more attention to the film orientation and grain boundary.

Replacing the kinetically sluggish and energy-intensive oxygen evolution reaction (OER) at the anode with the oxidation of more kinetically and thermodynamically favorable small organic molecules is a promising strategy for boosting hydrogen production. This study focuses on sustainable hydrogen generation at the cathode facilitated by the ethylene glycol oxidation reaction (EGOR) at the anode, coupled with the production of value-added formate. For this, we designed and deposited cobalt- and iron-based fluorinated two-dimensional (2D)-nanosheets (2D-CoFe@OF) through a straightforward hydrothermal method onto a nickel foam substrate (NF). The resulting 2D-CoFe@OF/NF exhibits an anodic potential that is 100 mV lower in a 0.5 M EG-added 1.0 M KOH electrolyte to achieve a benchmark electrolysis current density of 10 mA cm^–2, compared to a pure 1.0 M KOH electrolyte. Additionally, assembling two identical 2D-CoFe@OF/NF||2D-CoFe@OF/NF electrode-based electrolyzers resulted in a 150 mV reduction in operating cell voltage when electrolyzing at 150 mA cm^–2, particularly when the OER was replaced by EGOR, thereby demonstrating a significant improvement in energy efficiency. Under this condition, the electrolyzer demonstrated a nearly 100% Faradaic current efficiency for the hydrogen evolution reaction (HER). Furthermore, the practical application of this system studied with an EG-seawater electrolyzer suggests its potential to replace freshwater with abundant seawater, thereby expanding the horizon for sustainable hydrogen generation. This study, thus, highlights the promising potential of the 2D-CoFe@OF nanosheets on EGOR in seawater, advancing green hydrogen technology toward a more sustainable future.

In order to study the methane adsorption characteristics of the sea–land transition phase, the shale of Shanxi Formation of the Lower Permian in the Ordos Basin is analyzed in terms of organic geochemical characteristics, pore structure, and methane adsorption capacity (MAC). The total organic carbon (TOC) content ranges from 0.78 to 14.40 wt % (6.26 wt % on average). The organic matter belongs to type III kerogen and is in the overmature stage. The main content of these samples is quartz, followed by clay minerals. Under the experimental condition of 60 °C, the Langmuir volume (V_L) and Langmuir pressure (P_L) of the studied shale samples were in the range of 0.85–5.54 cm³/g and 0.95–4.46 MPa, respectively. V_L is positively correlated with micropore volume (PV_micro), micropore specific surface area (SSA_micro), and TOC content in two stages. Correlation will be better at higher TOC (TOC >5%). Only in samples with low TOC content (TOC <5%), the clay mineral content shows a weak positive correlation with V_L. In addition, the MAC showed an inverse correlation with temperature and a positive correlation with pressure. Overall, TOC content, microporous structure, pressure, and temperature are the main factors controlling the MAC of sea–land transition phase shales. Based on the Langmuir model, the functional relationship between MAC and TOC content, clay mineral content, and depth was established by comprehensively considering the factors affecting the MAC of shales. As pressure plays a major role in shallow buried depth, an increase in depth is accompanied by an increase in pressure, which also means that the MAC grows rapidly until it reaches a peak value. However, the role played by temperature gradually strengthens, and the inhibition of methane adsorption by the temperature becomes more and more pronounced as the depth continues to increase, ultimately causing the MAC to continue to decline once it has reached a peak value. The maximum MAC is between 1020 and 1340 m.

Exploring a diverse portfolio of technologies for decarbonization is crucial to understanding the potential impacts of different technological solutions and their associated environmental implications. Using high-octane, high-sensitivity biofuel blends in co-optimized multimode engines can increase engine efficiency and reduce vehicle emissions. The multimode engine research focuses on the benefits of light-duty vehicle engines, which can operate in multiple modes depending on the vehicle’s load. Low-temperature combustion can improve efficiency and reduce emissions (such as those from oxides of nitrogen and particulate matter) during low-load operation, while spark ignition performance is maintained in high-load operation. These advanced engines can be optimized to run on blends of biobased fuels. This analysis models scenarios for potential market adoption of co-optimized multimode vehicles fueled by three different bioblendstocks: ethanol, isopropanol, and isobutanol. An integrated modeling approach is used to forecast the energy and environmental impacts of the deployment of co-optimized multimode vehicles and fuels in the light-duty sector over the 2020-to-2050 time horizon. The multidisciplinary approach combines vehicle sales modeling, system dynamics modeling of the biorefining industry, and life cycle assessment to estimate the emissions and energy benefits. The models consider market forces such as consumer preferences for vehicle attributes, biofuel supply and demand dynamics subject to biorefinery capacity build-out and bioresource constraints, and forecasted changes to the U.S. bulk energy system over time. Market adoption of co-optimized vehicles is evaluated across a wide parameter space for incremental vehicle cost and engine efficiency improvement. This analysis reveals that the deployment of co-optimized multimode fuels and vehicles results in up to a 5% reduction in annual sector-wide life cycle greenhouse gas (GHG) emissions by 2050, relative to a business-as-usual scenario, but is also indicates environmental trade-offs, such as higher life cycle water-use. Emission benefits could potentially increase beyond 2050, as the new technologies penetrate the market and gain a foothold. Results also show that, under certain circumstances, vehicles with engines co-optimized for use with high-octane, high-sensitivity biofuel blends can be cost-competitive with conventional gasoline, while reducing GHG emissions. Our modeling results indicate that co-optimized multimode fuels and engines can be strategically leveraged in tandem with electrification to decarbonize the light-duty sector. Co-optimized vehicles could play a role in the early years of the time horizon, while electric vehicles (EVs) could become more competitive in the later years, highlighting the complementary benefits of these technologies for GHG reductions.

The established practice of wood ash disposal in landfills removes valuable elements, such as metals and plant nutrients, from the utilization cycle. In order to use the residual material wood ash as a secondary raw material and to conserve important natural resources (landfill space, mineral, and metallic raw materials), a treatment process must be developed. As a basis for such a process, fundamental knowledge of element solubility is required. Therefore, a sequential extraction process describing the mobility of the ash-forming elements was carried out for three ash fractions from a wood-fired heat and power plant. This work describes the extraction of 24 elements from ash by four sequentially applied extractants. As an aqueous solvent, bidest. water was used, acetic acid was used as the acidic solvent, hydroxylamine hydrochloride was used as the reducing solvent, and ammonium acetate with hydrogen peroxide was used as the oxidizing solvent. Element concentrations in the individual extractants were determined by ICP–OES. We found that the extraction is influenced by the ash fraction, the particle size, and the element-specific behavior during ash formation. Extractability is higher from filter and cyclone ash fractions compared to grate ash as well as from smaller particle size fractions within grate ash compared to coarse grate ash particles. The majority of the metals were acid-soluble. In parameter studies, we found that extractability can be increased by using stronger solvents, grinding the ash, and a longer extraction time. The results provide information on (I) the environmental mobility of the ash-forming elements and (II) suitable solvents and process parameters for the processing of ashes, with the aim of a consistent recycling of valuable substances and nutrients.

Coalbed methane (CBM), as an associated resource of coal, has important strategic energy strategic significance. However, most reservoirs in China have low permeability, which poses challenges for CBM mining. Based on the background of acidification to increase CBM production, the macroscopic mechanics seepage, mesoscopic morphology observation, and microscopic pore measurement experiments of coal under acid treatment were carried out, and the influence of acid on macro-meso-micro characteristics of coal and insights into enhancing CBM were revealed. It is found that acid corrosion can weaken the strength and energy storage capacity of coal, and obvious toughness characteristics appear under postpeak stress loading. The effect of acidification on the permeability of coal is time-dependent. In the early stage of acidification, the sensitivity index is larger, rendering the permeability more susceptible to variations over time. However, as the process advances to later stages, blindly increasing acidification time gradually weakens the effect of permeability enhancement and even decreases. Evidence of acid etching of mineral components in fracture peaks and valleys was found under the microscope, with originally blocked pores achieving unblocking and connecting to primary pores, and it was also surprising to find that acidification reaction increased the surface roughness of samples. Furthermore, following acid treatment, the samples exhibited an increase in the average pore diameter, pore volume, porosity, and Knudsen number. The pore fractal dimension and tortuosity decreased, which made it easy for gas diffusion and seepage activities. The research results have guiding significance for CBM energy development and underground disaster prevention.

Although CO₂ hydrate formation technology in porous media is regarded as an effective means to address carbon emissions, the effects of the physicochemical properties of porous media on the growth characteristics of hydrates remain to be studied. In this work, the influence mechanism of the molecular/pore structures of three different ranks of coals (R_o, max = 0.99% for XZ-02, 1.39% for YT-09, and 2.29% for ZC-15) on CO₂ hydrate formation was studied at 40, 70, and 100% water saturation rates via the excess gas method. The results show that the adsorption and hydrophobicity controlled by the molecular structure are beneficial for the synthesis of CO₂ hydrates. A greater amount of CO₂ adsorbed on the coal surface increased the gas pore pressure, shortened the induction time, and promoted hydrate formation. Moreover, a strongly hydrophobic surface is conducive to the nucleation of CO₂ hydrates. CO₂ hydrates are synthesized mainly in macropores (>50 nm). The macropores of YT-09 are mainly 400–10,000 nm in size, which is much larger than the critical pore size (radius of 58.68 nm) of the capillary effect, avoiding the influence of the nanopore constraint effect and promoting the synthesis of hydrates. XZ-02 and ZC-15 contain smaller macropore sizes and throats, greatly shortening the induction time of hydrate formation while hindering mass transfer, resulting in less hydrate synthesis. The water consumption and conversion rate decrease with increasing water saturation. In addition, water cannot be completely converted into CO₂ hydrate because of the influence of mass transfer in the late stage of massive hydrate synthesis. CO₂ hydrates tend to form in the cementation mode at 40 and 70% water saturation, whereas they form in the floating mode at 100% water saturation. Coal with low apparent density and wide macropores is more suitable as a porous medium for solidifying and storing CO₂ in the form of a hydrate. This work provides theoretical guidance for CO₂ capture and storage in coal measure gas hydrate reservoirs.

Enhanced oil recovery (EOR) is the process of residual oil production in the tertiary stage. It requires the injection of external energy sources such as gases, chemicals, and thermal energy in the reservoirs. Chemical enhanced oil recovery (CEOR) can boost the oil recovery significantly by improving the microscopic displacement of oil trapped in the pore spaces of the reservoir rock. Each type of chemical flooding depends on different mechanisms to enhance the oil recovery. Surfactant flooding aims to reduce interfacial tension, alter the wettability of rock to more water wet, and promote the displacement of oil in porous media. The surfactant performance can be affected by temperature, salinity, pH, surfactant concentration, and adsorption. Hence, a comprehensive study of fluid–fluid and rock–fluid interactions is required before any surfactant flooding process. This characterization study aims to evaluate the cationic surfactants, tetramethylammonium chloride (TMAC) and hexadecyltrimethylammonium chloride (HTMAC), which have the potential to be EOR fluids for carbonate reservoirs in harsh conditions. The surfactant solutions were prepared in seawater. TGA, FTIR, solubility and compatibility, IFT, contact angle, and zeta potential tests have been carried out to characterize these surfactants. The obtained results revealed that the cationic surfactants are stably compatible under harsh conditions. Moreover, the results demonstrated that HTMAC has high potential to be used as an EOR fluid by lowering the IFT from 21.4 to 0.16 mN/m and shifting the contact angle from 159.6 to 40° within 24 h of aging at a low concentration (100 ppm). In contrast, TMAC has little effect on IFT; it reduced IFT from 21.4 to 10.2 mN/m and could not alter the wettability to a water-wet condition. Further investigation has been done using a cosurfactant (SS-885) with TMAC to evaluate the effect of this mixture on IFT and contact angle. Using a low concentration (100 ppm) of the mixture reduced the IFT to an ultralow value (0.03) mN/m but had little effect on the contact angle.

Ammonia (NH₃) is a promising zero-carbon fuel with an exceptionally high hydrogen density. However, the feasibility of employing ammonia as a future fuel faces several obstacles including low combustion intensity. Co-firing reactive carbon-neutral fuels, such as oxymethylene ethers (OME_n) with NH₃ emerges as an effective approach to enhance NH₃ combustion. This work investigates the laminar flame propagation of NH₃ cofired with dimethyl ether (DME), dimethoxymethane (OME₁), and methoxy(methoxymethoxy)methane (OME₂) using a high-pressure high-temperature constant-volume combustion vessel. Laminar burning velocities (LBVs) are measured at an initial temperature of 423 K and pressures of 1–10 atm. A kinetic model for NH₃/OME_n combustion is developed and validated against the measured LBVs in this study, as well as LBVs and speciation data in literature. Both the experimental and kinetic modeling studies indicate the positive effect of cofiring of OME_n on ammonia combustion enhancement. The LBV levels of the NH₃/OME_n mixture can be similar to that of methane. The effects of cofiring fuel compositions, equivalence ratios, and pressures are investigated using modeling analysis and the modified fictitious diluent gas method. In mixture combustion, the reaction pathways of ammonia, DME, OME₁, and OME₂ remain almost unchanged compared to single fuel combustion, despite the slight contribution of C–N interaction. Combustion enhancements result from both chemical effects and thermal effects and their contribution ratios vary according to equivalence ratios and fuel compositions. At ϕ = 1.6, the contribution of chemical effects increases in the order 50%NH₃/50%DME, 50%NH₃/50%OME₁, and 50%NH₃/50%OME₂. Though there are similar LBVs for DME, OME₁, and OME₂, the mixture LBVs follow the sequence of 50%NH₃/50%DME < 50%NH₃/50%OME₁ < 50%NH₃/50%OME₂, which can be attributed to the influence of their lower heating values. A quasi-square relationship between normalized LBVs and energy fraction can be derived by using the correction of the energy fraction for the three NH₃/OME_n mixtures.