Frontiers in Energy最新文献

Ammonia, as a zero-carbon fuel, has great potential for meeting decarbonization targets in the internal combustion engine sector. This paper summarizes recent studies in which ammonia is used as a fuel for compression-ignition engines. Due to its low combustion reactivity, ammonia must be used in conjunction with a high reactivity fuel, such as diesel, to ensure stable engine operation. Currently, two main approaches are used to supply ammonia to the engine combustion chamber: ammonia port injection and in-cylinder direct injection. In the two routes, ammonia-diesel engines commonly face challenges such as low ammonia energy rate (AER), limited thermal efficiency, and high emissions of nitrogen-containing pollutants, especially under high ammonia substitution conditions. To address these challenges, this study reviews combustion technologies capable of achieving relatively high AER, such as premixed charge compression ignition (PCCI) and reaction-controlled compression ignition (RCCI), and analyzes their impact on combustion and emissions characteristics. This paper also examines combustion technologies under ultra-high AER conditions and finds that technologies such as diesel pilot injection and ammonia-diesel stratified injection can support stable engine operation. This review provides insights into current progress, remaining challenges, and future directions in ammonia-diesel engine combustion technologies.

Hydrogen storage is a critical component in transition to clean energy systems and the promotion of sustainable practices across various industries. The primary technical challenge lies in designing adsorbent materials that effectively balance both volumetric and gravimetric storage capabilities while ensuring operational reliability. Achieving this balance is essential for the efficient and practical application of hydrogen in fuel-based systems. Recently, in Nature Chemistry, Stoddart et al. introduced a straightforward and precise method: multivalent hydrogen bonding facilitates molecular linkage at defined nodal points in hydrogen-bonded organic frameworks (HOFs). This methodology demonstrates simultaneous optimization of hydrogen storage performance, achieving notable volumetric (53.7 g/L) and gravimetric (9.3 wt%) capacities under dynamic thermo-pressure cycling conditions.

Developing low-cost and high-performance acid-resistant electrocatalysts is essential for the industrialization of hydrogen production via proton exchange membrane water electrolysis. Herein, an acid-stable bimetal phosphide (NiCoP) catalyst wrapped around silver nanowires (Ag NWs), forming a seamless conductive core-shell structure (NiCoP@Ag NWs), is reported to enhance the hydrogen evolution reaction (HER). The incorporation of Ag NWs creates an uninterrupted conductive network that facilitates efficient electron transfer and provides a large electrolyte-accessible surface area for mass transport. The synergistic interaction among Ni, Co, and P further optimizes electronic structure and decreases the energy barrier of NiCoP@Ag NWs for H* adsorption and desorption. More importantly, the distinctive core-shell structure imparts outstanding acid resistance to the catalyst. Notably, NiCoP@Ag NWs displays remarkable HER performance, with a low overpotential of 109 mV (significantly lower than Ni₂P@Ag NWs at 144 mV and Co₂P@Ag NWs at 174 mV) at a current density of 10 mA/cm², along with excellent durability exceeding 100 h in acidic media. These features surpass most reported non-noble metal catalysts, demonstrating extraordinary potential for practical hydrogen production via acidic water electrolysis.

The increasing accumulation of discarded plastics has already caused serious environmental pollution. Simple landfills and incineration will inevitably lead to the loss of the abundant carbon resources contained in plastic waste. In contrast, photoconversion technology provides a green and sustainable solution to the global plastic waste crisis by converting plastics into hydrogen fuel and valuable chemicals. This review briefly introduces the advantages of photoconversion technology and highlights recent research progress, with a focus on photocatalyst design as well as the thermodynamics and kinetics of the reaction process. It discusses in detail the degradation of typical common plastic types into hydrogen and fine chemicals via photoconversion. Additionally, it outlines future research directions, including the application of artificial intelligence in catalyst design. Although photocatalytic technology remains at the laboratory stage, with challenges in catalyst performance and industrial scalability, the potential for renewable energy generation and plastic valorization is promising.

The non-uniform pore size distribution and high flammability of commercial separators pose significant challenges to the safe application of high-energy-density lithium-ion batteries. In this study, a flame-retardant composite separator (P@HLi) with high thermal stability was successfully developed, which not only suppressed lithium dendrite growth but also improved high-temperature cycling performance of batteries and significantly enhanced their thermal safety. Li//Li symmetric batteries equipped with P@HLi-20 separators demonstrated stable cycling for over 600 h at a low polarization potential (approximately 50 mV), effectively reducing the formation of “dead lithium” and lithium dendrites. The LFP//Li and NCM811//Li cells with P@HLi-20 separators delivered initial discharge specific capacities of 142.0 and 167.9 mAh/g, respectively. Notably, the LFP//Li battery with P@HLi-20 separator showed excellent high-temperature cycling performance, maintaining 98.0% capacity retention and a discharge capacity of 131.1 mAh/g after 100 cycles at 1 C at 90 °C. Furthermore, pouch cells assembled with P@HLi-20 separators exhibited reductions of 52.67% in peak heat release rate (PHRR) and 68.42% in total heat release (THR) compared to those using Celgard separators, demonstrating superior thermal safety. These results confirm that the P@HLi separator offers comprehensive improvements in both electrochemical performance and safety characteristics.

Diethyl ether (DEE, C₄H₁₀O) has emerged as a promising renewable alternative to conventional diesel fuels, offering potential solutions for sustainable energy development. This review systematically examines the fundamental combustion characteristics of DEE, including pyrolysis and oxidation behaviors, kinetic modeling, and actual combustion characteristics. It comprehensively summarized the key research progress and main findings in this field. Research has indicated that DEE demonstrates excellent ignition performance, whether used alone or as an additive, and significantly reduces soot formation during combustion by limiting the discharge of C₃-C₄ hydrocarbon species. However, a complete mechanistic understanding of DEE combustion still remains limited by the lack of key coupling reaction pathways, which directly restricted the accuracy of the reaction kinetic model. At the actual combustion level in devices, the effects of DEE on engine performance, combustion behavior, and emissions has been investigated. Although a large number of experiments have confirmed that DEE has a significant improvement effect in the above aspects, certain performance degradation phenomena and their internal mechanism still require further elucidation. Based on these insights, this review also analyzes the key challenges facing DEE in practical applications and discusses possible solutions, aiming to build a complete research framework spanning from fundamental studies to engineering application future development.

The electrochemical CO₂ reduction reaction (CO₂RR) provides a promising approach to mitigate the global greenhouse effect by converting CO₂ into high-value chemicals or fuels. Noble metal-based nanomaterials are widely regarded as efficient catalysts for CO₂RR due to their high catalytic activity and excellent stability. However, these catalysts typically favor the formation of C1 products, which have relatively low economic value. Moreover, the high cost and limited availability of noble materials necessitate strategies to reduce their usage, often by dispersing them on suitable support materials to enhance catalytic performance. In this study, a novel metal-based support, zirconium phosphate Zr₃(PO₄)₄, was used to anchor ultrasmall palladium nanoparticles (pre-ZrP-Pd). Compared to the reversible hydrogen electrode, the pre-ZrP-Pd achieved a maximum Faradaic efficiency (FE) of 92.1% for ethanol at −0.8 V versus RHE, along with a peak ethanol current density of 0.82 mA/cm². Density functional theory (DFT) calculations revealed that the strong metal-support interactions between the ZrP support and Pd nanoparticles lead to an upward shift of the Pd d-band center, enhancing the adsorption of CO* and promoting the coupling of CO and CO to produce ethanol.

To mitigate the adverse effects of high concentrations of Cl⁻ ions in seawater on electrolysis efficiency, it is essential to develop efficient and stable electrocatalysts. Based on this need, CuCo-ZIF NCs were used as a precursor to synthesize a CuCo-TA@FeOOH heterojunction composites, specifically designed for the oxygen evolution reaction (OER) in alkaline seawater, through a combination of acid etching and a self-growth method. The resulting material exhibits an OER overpotential of 234 mV at 10 mA/cm² in alkaline freshwater and 256 mV at 10 mA/cm² in seawater electrolyte. This performance is attributed to synergistic interactions at the heterojunction interfaces, which enhances the specific surface area, offers abundant active sites, and improves mass transfer efficiency, thereby increasing catalytic activity. Moreover, at a current density of 100 mA/cm², it maintains stable performance for up to 300 h without deactivation. This remarkable stability and corrosion resistance stems from the synergistic effect at the CoOOH and FeOOH interface formed during reconstruction, which facilitates electron transfer, optimizes the electronic structure during the reaction process, and effectively suppresses the chlorine evolution reaction (CER). This study offers a valuable reference for the rational design of high-performance electrocatalysts for alkaline seawater oxidation.

Sodium-ion batteries (SIBs) exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources. Triggering lattice oxygen redox (LOR) in P2-type transition metal oxides is considered a promising approach to enhance energy density in SIB cathodes, providing high operating potential and substantial capacity. However, irreversible phase transitions associated with LOR, particularly from prisms (P-type stacking) to octahedrons (O-type stacking), lead to severe structural distortions and sluggish Na⁺ diffusion kinetics. In this work, an Al-substitution strategy is proposed to suppress the formation of O-type stacking and instead promote the formation of a beneficial Z phase. The flexible Al-O bonds accommodate asymmetric variations in their occupied states during the sodiation process, mitigating local structural distortions through Al-O bond contraction. Stabilization of the local structure ensures the maintenance of a robust Na⁺ diffusion pathway. As a result, the Al-substituted cathode achieves a low Na⁺ diffusion barrier of 0.47 eV and delivers a capacity of 86 mAh/g even at a high current density of 1 A/g within 1.5–4.5 V, maintaining 62.5% capacity retention over 100 cycles.