Frontiers in Energy最新文献

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.

NH₃ has emerged as a promising candidate for low-carbon gas turbines, with NO_x emission issues being mitigated by air-staged combustion. However, the role of fuel/air mixing quality (represented by unmixedness) in NO_x formation in NH₃ systems remains poorly explored. In this study, the characteristics of NO_x formation under the effects of unmixedness have been numerically investigated using an NH₃/CH₄ fired air-staged model combustor consisting of perfectly stirred reactors (PSRs) and plug flow reactors (PFRs), employing the 84-species, 703-reaction Tian mechanism under H/J heavy duty gas turbine conditions. It was found that a primary-stage equivalence ratio of 1.2–1.5 corresponds to a low NO_x formation region under perfectly mixed fuel and air conditions. In this region, a relatively low NO_x formation is achieved when the unmixedness is less than 0.12 and NO_x formation exhibits low sensitivity to fuel/air unmixedness. Based on these findings and the fact that the air-staged combustion loses its advantage in reducing NO_x emissions when the unmixedness exceeds 0.12 across all equivalence ratios, recommended mixing quality thresholds for different equivalence ratios are proposed to guide combustor design and operation optimization. A parametric study of chemical reaction pathways at different unmixedness levels in the two stages demonstrates that NO_x is mainly formed in the main combustion zone of the secondary stage via the HNO pathway, which results in NO_x formation rising to thousand ppm when unmixedness exceeds 0.3, although NO_x reduction through NHi and N₂O pathways partially offsets contributions from the HNO and thermal NO_x pathways. To leverage the NO_x reduction potential of the NHi and N₂O pathways, the residence time in both stages should be carefully adjusted to help suppress NO_x to as low as 48 ppm. The results of this study are important for engineering applications, providing guidance for the design of NH₃ fired combustors aimed at significantly reducing NO_x formation.

The electrochemical oxidative coupling of methane (EOCM), integrated with CO₂ electrolysis enabled by high-temperature electrolysis technology, represents a promising pathway for methane utilization and carbon neutrality. However, progress in methane activation remains hindered by low C₂ product selectivity and limited reaction activity, primarily due to the lack of efficient and stable catalysts and rational design strategies. A critical focus of current research is the development of catalysts capable of stabilizing reactive oxygen species to facilitate C-H bond activation and subsequent C-C bond formation. Herein, an easily fabricated composite electrode consisting of perovskite La_0.6Sr_0.4MnO_3-γ and Ce-Mn-W materials with (Ce_0.90Gd_0.10)O_1.95 as the support was developed, demonstrating efficient activate methane activation. Combined theoretical and experimental investigations reveal that the designed composite electrode stabilizes active oxygen species during the oxygen evolution reaction (OER) while exhibiting superior methane adsorption capability. This design, leveraging oxygen species engineering and interfacial synergy, significantly enhances electrochemical methane coupling efficiency, establishing a strategic framework for advancing high-performance catalyst development.

High entropy alloys (HEAs) have gained significant attention in electrocatalysis research due to their distinctive multi-element composition, intricate electronic structure, and superior properties. By harnessing multi-component synergy, precise electron regulation, and the high-entropy effect, HEA electrocatalysts exhibit remarkable catalytic activity, selectivity, and stability. These materials demonstrate outstanding catalytic performance in a variety of electrocatalytic small molecule reduction reactions, including oxygen reduction (ORR), hydrogen evolution (HER), and CO₂ reduction (CO₂RR), making them promising candidates for clean energy conversion and storage applications, including fuel cells, metal-air batteries, water electrolysis, and CO₂ conversion technologies. This review highlights recent advancements in HEA electrocatalyst research, focusing on their synthesis, characterization, and applications in electrocatalytic small molecule reduction reactions. It also explores the underlying mechanisms of the high-entropy effect, multi-component synergy, and structural design. Finally, it discusses key challenges that remain in the application of HEAs for electrocatalytic small molecule reduction and outlines potential directions for future development in this field.

This study employs the method of embedding voltage leads within three cells of an electrolysis stack to investigate the quantitative impact of the electrolysis cells and their interfaces on overall stack performance. A 900-h stability test was conducted at a constant temperature of 750 °C with a current density of 500 mA/cm² and 60 vol.% (volume fraction) water steam content. The results indicate the electrolysis voltage of the stack increased by 0.213 V, while the voltage across the three cells increased by 0.268 V. Post-mortem analysis reveals changes in the three-phase boundary (TPB) and porosity of the Ni-YSZ electrodes across different cells. These structural changes explain the variations in both ohmic resistance and polarization resistance. In contrast, the voltage drop across the current-collecting interface between the interconnect and the cell decreases by 0.055 V, accounting for 25.82% of the total stack degradation. Improved interface contact helps inhibit stack degradation. Future work will further investigate the stability of stack components and their interfaces, aiming to optimize stack design.

The substitution of traditional fossil fuels with renewable energy sources is a crucial endeavor for achieving carbon neutrality targets. However, the intermittency of solar, wind, and other renewables poses significant challenges to the power grid. Power-to-X (P2X) technologies play an essential role in enabling the efficient consumption of renewable energy. High-temperature solid oxide electrolysis cells (SOECs) to convert CO₂ offer a promising method for CO₂ conversion, allowing renewable electricity to be stored in chemical form and facilitating the resourceful utilization of carbon resources. In this paper, the mechanism of CO₂ reduction through SOECs is reviewed, two pathways for converting CO₂ to chemicals via SOECs are summarized, and the current markets and manufacturers of SOECs are elucidated. Based on this discussion and analysis, the main challenges and development directions for the large-scale application of SOECs in CO₂ conversion are further proposed.

Developing environmentalyl friendly and energy-efficient CO₂ adsorbents for post-combustion capture is a critical step toward achieving toward carbon neutrality. While aqueous amines and metal oxides have play pivotal roles in CO₂ capture, their application is limited by issues such as secondary pollution and high energy consumption. In contrast, Zn-based metal-organic frameworks (Zn-based MOFs) have emerged as a green alternative, offering low toxicity reduced regeneration temperatures, and high efficiency in both CO₂ adsorption and catalytic conversion into valuable fuels and chemicals. This mini review begins with a general introduction to MOFs in CO₂ capture and conversion, followed by an overview of early studies on Zn-based MOFs for CO₂ capture. It then summarizes recent research advancements in Zn-based MOFs for integrated CO₂ capture and conversion. Finally, it discusses key challenges and future research directions for post-combustion CO₂ capture and conversion using Zn-based MOFs.

The oxygen reduction reaction (ORR) plays a crucial role in key processes of fuel cells and zinc-air batteries. To enable commercialization, reducing the platinum (Pt) content and increasing the specific activity per unit mass is essential. A promising approach involves synthesizing of Fe-N-C precursors via the polyaniline (PANI) pathway, which ensures a uniform distribution of Fe-N-C species and facilitates the subsequent adsorption of platinum ions. This leads to the formation of Pt-Fe bimetallic alloys. The synergistic interaction between Pt and Fe-N-C sites promotes the homogeneous dispersion of Pt and the formation of smaller particle sizes, which in turn enhances intrinsic activity and stability of the catalyst. Notably, the Pt/Fe-N-C catalyst, featuring an ultra-low Pt loading of just 1.79 wt%, exhibits a remarkable doubling of mass activity compared to conventional catalysts. Moreover, zinc-air batteries using this catalyst achieve an impressive peak power density of 200 mW/cm².

Single-atom transition metal-nitrogen-doped carbons (SA M-N-Cs) catalysts are promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, enhancing their performance for practical applications remains a significant challenge. This review summarizes recent advances in enhancing the intrinsic activity of SA M-N-C catalysts through various strategies, such as tuning the coordination environment and local structure of central metal atoms, heteroatom doping, and the creation of dual-/multi metal sites. Additionally, it discusses methods to increase the density of M-N_x active sites, including chelation, defect capture, cascade anchoring, spatial confinement, porous structure design, and secondary doping. Finally, it outlines future directions for developing highly active and stable SA M-N-C catalysts, providing a comprehensive framework for the design of advanced catalysts.