ACS Applied Energy Materials最新文献

This study functionalizes MXene surfaces using silane coupling agents to prepare organo-MXene (MX-C═C, MX-NH₂, MX-NHC) with distinct functional groups (C═C, NH₂, NHC), which are further in situ composited with bimetallic metal–organic frameworks (Ni, Co-MOF) to develop NiCo-MOF@organo-MX composite electrode materials. Structural characterizations confirm that the functionalization effectively alleviates MXene sheet stacking and regulates the morphology and distribution density of MOF particles. Electrochemical tests reveal that NiCo-MOF@MX-NHC exhibits optimal performance, achieving a specific capacitance of 1682.6 F g^–1 at 1 A g^–1 and retaining 68% capacity after 5000 cycles at 20 A g^–1. The NH–CH₃ functional group enhances pseudocapacitive behavior and charge transfer efficiency by modulating MXene surface active site density and MOF dispersion. Furthermore, an asymmetric supercapacitor assembled with tetraethylammonium tetrafluoroborate/acetonitrile (TEMA-BF₄/AN) organic electrolyte demonstrates a wide voltage window of 2.4 V, delivering a high energy density of 41.5 Wh kg^–1 at 24,000 W kg^–1 power density, while successfully powering LED devices, validating its practical potential. This work provides theoretical and technical foundations for designing high-performance MOF@MXene composite electrodes.

The structure of biomass precursors plays an important role in determining the structure of hard carbon. However, the effects of biomass structures on the closed pore sodium storage performance of the resultant hard carbon have yet to be explored comprehensively. As this limitation has hindered the progress of high-capacity hard carbon anodes, three types of starch samples with varying amylopectin contents─namely, amylopectin, corn starch, and high-amylose starch─were selected in this study to prepare hard carbon microspheres as anodes in sodium-ion batteries. Amylopectin, composed of both α-1,6 and α-1,4 glycosidic bonds, contains more hydroxyl groups than amylose. Starch with a high amylopectin content generates more C═O and C═C bonds through dehydration during stabilization, facilitating chain cross-linking. This cross-linking effect creates narrow and long graphite microcrystalline structures, leading to the formation of large closed pores during carbonization. The hard carbon microspheres derived from the precursor with a high amylopectin content exhibit a higher closed-pore area of 519 m² g^–1, resulting in a higher reversible specific capacity of 333.2 mAh g^–1 and remarkable cycling stability. This study reveals the structure–function relationship between the amylopectin content and closed pore formation in hard carbon, providing valuable insights into the future application of starch-based carbon in sodium-ion batteries.

NaCl contamination of membrane-electrode assemblies is a critical challenge for the stability and long-term durability of proton-exchange membrane fuel cells (PEMFCs), particularly in marine and humid environments. In this study, we systematically investigated the degradation behavior of PEMFCs under NaCl exposure by decoupling the individual effects of Na⁺ and Cl^– ions through electrochemical and spectroscopic analyses. Electrochemical impedance spectroscopy revealed that Na⁺ had a minimal impact on proton conductivity, as evidenced by the stable ohmic resistance over time. In contrast, Cl^– significantly increased the charge transfer resistance and decreased the electrochemically active surface area, indicating strong catalyst poisoning. X-ray photoemission spectroscopy analysis showed broadened Pt 4f peaks and the emergence of Pt⁴⁺ states, while white X-ray absorption near-edge spectroscopy revealed an increase in the white-line intensity, reflecting the changes in electronic structure at the Pt surface. Transmission electron microscopy further confirmed the Pt nanoparticle growth from 2.4 to 4.0 nm after prolonged operation in both NaCl-free and NaCl-containing cells, which is consistent with Ostwald ripening rather than Cl^–-induced dissolution. Collectively, these results demonstrate that Na⁺ has a limited effect on membrane properties, while Cl^– interacts strongly with the catalyst. This study offers a systematic multimodal analysis of salt-induced failure modes in PEMFCs and provides critical insights into their deployment in chloride-rich environments.

Designing electrocatalysts that combine high activity, selectivity, and stability is critical for an efficient oxygen evolution reaction (OER). Previous studies show that modifying the OER catalysts, such as oxide, hydroxides, layered double hydroxides, etc., employing the chiral-induced spin selectivity (CISS) effect enhances the activity of the catalyst beyond its thermodynamic limit. However, to the best of our knowledge, inducing the CISS effect into a bimetallic metal organic framework (MOF) has not been studied yet. In this study, we report for the first time the incorporation of CISS in a NiFe-MOF-based thin-film catalyst using chiral naphthalene diimide (NDI) molecules that form helical supramolecular structures. Details of structural and spectroscopic analyses confirm the uniform Ni/Fe incorporation in the organic framework and successful chiral modification. The chiral R- and S-NiFe-MOF electrodes exhibit outstanding OER performance in 1 M KOH, requiring overpotential of only 290 mV at 10 mA cm^–2 and Tafel slopes of 59 mV dec^–1, markedly superior to the racemic analogue (325 mV, 76 mV dec^–1). Oxygen evolution is measured quantitatively, and it reveals that the O₂ evolution rate using the chiral catalyst is ∼1.5-fold higher than the achiral one. Significant reduction of the formation of the byproduct hydrogen peroxide while using chiral catalysts highlights the role of spin-polarized electron transfer that promotes the formation of triplet O₂. Hence, this dual strategy of bimetallic synergy and chiral functionalization provides a robust platform for next-generation OER electrocatalysts for sustainable water-splitting and renewable-energy applications.

Atomic layer deposition (ALD)-derived SnO₂ is an attractive electron transport layer (ETL) for scalable, high-performance perovskite solar cells (PSCs) owing to its excellent uniformity and compatibility with industrial processing. However, its intrinsic oxygen vacancies and surface imperfections hinder efficient charge extraction and interfacial stability. Herein, we introduce a reactive ion etching-assisted surface engineering (RIE-ASE) strategy that integrates chemical oxidation and physical ion bombardment to finely tailor the surface chemistry of ALD-SnO₂. Our systematic surface engineering approach via RIE treatment demonstrates effective passivation of oxygen vacancies and formation of a well-defined SnO₂ surface, enhancing interfacial quality and electronic characteristics. The RIE-ASE-treated layers exhibit improved band alignment with perovskite absorbers and preserved morphological integrity. When incorporated into PSCs, the optimized RIE-ASE-modified single-layer ALD-SnO₂ yields a champion power conversion efficiency (PCE) of 23.13%, surpassing that of UV-Ozone-treated counterparts (21.88%). In addition, the RIE-ASE-treated devices exhibit negligible hysteresis and excellent reproducibility across 20 independent cells. Furthermore, the devices maintain over 95% of their initial PCE after 1000 h under dry room conditions (20 °C, 15% relative humidity), outperforming the 87% retention observed for the UV-ozone-treated control. This study establishes RIE-ASE as a rapid, vacuum-compatible, and highly reproducible method for defect passivation and energy-level tuning of ALD-SnO₂, providing a viable pathway toward scalable and commercially relevant fabrication of efficient and stable perovskite solar cells.

Electrical double-layer capacitors offer high power density and long cycle life but are limited by moderate energy density. We investigate a strategy to improve their performance using quaternary electrolytes containing two distinct cations and two distinct anions. Our theoretical analysis shows that such electrolytes outperform pure ionic liquids and conventional mixtures sharing a common ion. We validate this approach experimentally using [EMIM][BF₄] mixed with lithium salts, characterizing their local structure and electrochemical behavior via NMR, Raman spectroscopy, conductivity measurements, and electrochemical testing. We further demonstrate that the enhancement depends sensitively on electrode microporosity, underscoring the interplay between electrolyte composition and pore structure.

Probing earth-abundant catalytic systems with multiple functionalities, remarkable activity, and robust stability is pivotal to sustainable H₂ production. Developing these catalytic systems not only mitigates cost and scalability challenges but also improves overall efficiency by enhancing charge separation, accelerating redox kinetics, and strengthening structural durability under operational conditions. In this quest, S-scheme MoSe₂@CdSe–ZnO heterojunctions have been designed hydrothermally to examine photochemical (PC), electrochemical (EC), and photoelectrochemical (PEC) activity for H₂ production. 1, 2.5, and 5 wt % MoSe₂@CdSe–ZnO (1CMZ, 2.5CMZ, and 5CMZ) photocatalytic systems showed significantly higher PC performance than pure ZnO, exhibiting the optimum 3.67 mmol g_cat^–1h^–1 H₂ generation with an apparent quantum yield (AQY) of 28.9% (450 nm). The MoSe₂@CdSe–ZnO catalytic system is designed as a ternary heterostructure with a uniform hexagonal phase to minimize lattice mismatch, reduce interfacial defects, and enhance charge carrier mobility, ultimately boosting the photocatalytic efficiency of MoSe₂@CdSe–ZnO for water splitting. EC experiments revealed the phenomenal HER and OER performances of optimized 2.5CMZ, showing low overpotential values of 970 and 310 mV, respectively. PEC results validated the supremacy of 2.5CMZ as the photocurrent density and overpotential values are enhanced compared to electrochemical outputs. Density functional theory, band structure analysis, time-resolved photoluminescence, electrochemical impedance spectroscopy, and ex situ X-ray photoelectron spectroscopy investigations deduced the robust relation between theoretical outputs and experimental results in establishing an S-scheme reaction mechanism.

Photocatalysis holds great potential in sustainable environmental purification and carbon dioxide transformation. Nevertheless, the performance of semiconductor photocatalysts is significantly hampered by fast charge recombination. In this study, LaFeO₃ nanospheres were synthesized via a simple hydrothermal method and were subsequently combined with g-C₃N₄ nanosheets that had undergone mechanical activation and thermal condensation processes. Furthermore, Ag nanoparticles were homogeneously introduced into the composite through photodeposition and impregnation methods, to successfully construct a LaFeO₃/Ag/g-C₃N₄ Z-scheme heterostructure. Composition, microstructure, and photoelectrochemical properties of the photocatalysts were thoroughly investigated using X-ray analysis, microscopy, UV–vis absorption spectroscopy, and photoluminescence (PL) spectroscopy. The LaFeO₃/Ag/g-C₃N₄ composite exhibited outstanding photocatalytic CO₂ reduction performance, with CO and CH₄ yields of 7.55 and 1.90 μmol·g^–1·h^–1, respectively, which are 17.9 and 15.8 times higher than those of pure LaFeO₃. Additionally, the composite sample with 1% Ag loading demonstrated favorable degradation kinetics for rhodamine B (RhB) and tetracycline (TC) under visible light irradiation, with a remarkable RhB degradation rate of 98.58% within 75 min. Finally, the reduction of CO₂ to intermediate products such as *COOH was analyzed using in situ diffuse reflectance infrared Fourier transform spectroscopy (In-situ DRIFTs), and a plausible reaction pathway was proposed.

Zinc metal is one of the most promising anode materials for aqueous batteries. However, nonuniform deposition of zinc metal anodes and hydrogen evolution reactions (HER) severely affect the stability of aqueous zinc–ion batteries. Herein, a simple redox reaction between zinc metal and graphene oxide and a subsequent one-step replacement reaction were utilized to in situ fabricate rod-shaped zinc oxide, reduced graphene oxide (rGO), and Cu nanoparticles on the zinc anode surface. This ingenious design constructs an artificial gradient zinc-affinity interface layer (ZnO–rGO–Cu), which regulates the longitudinal electric field distribution, enabling Zn²⁺ to deposit uniformly along the gradient from bottom to top, thereby suppressing the dendrites growth. Besides, Cu nanoparticles and rGO partially isolate the zinc from the electrolyte to inhibit the unwanted HER. Moreover, these components reduce the interface contact angle with aqueous electrolytes, enhancing electrolyte affinity and electrochemical activity. Consequently, the Zn–rGO–Cu symmetric cells cycle stably for 1000 h at 1 mA cm^–2, and the half-cells achieve 1500 stable cycles at 2 mA cm^–2 with a high Coulombic efficiency of 99%. Furthermore, full cells paired with manganese-based and vanadium-based cathodes stably cycle 900 times at 0.5 A g^–1 and 600 times at 2 A g^–1, respectively. This study thus provides insights into rationally designing multifunctional interphase layers for high-performance zinc–ion batteries.

Fe(III) oxyhydroxides are promising electrocatalysts due to their redox properties, enhanced surface reactivity, and natural abundance as minerals, combined with their abilities to modulate the catalytic activities in the presence of dopant transition metal atoms, specifically Ni and Co. In this study, we investigate the electrocatalytic oxygen evolution reaction (OER) using Fe-oxyhydroxide clusters in a homogeneous aqueous medium by employing density functional theory (DFT). A water molecule coordinated to the Fe center of the Fe(III) oxyhydroxide cluster was converted to oxygen in a few sequential stepwise electron-transfer reactions analogous to the conventional OER. We first studied the free energy changes of the OER using small Fe(III) oxyhydroxide clusters and evaluated the effects of doping with Co, Ni, and Mn on their OER activity. Our investigations show that the OER activity improves in Fe₂ dimers with more terminal −OH ligands compared to cationic cases, and the neutral FeCo dimer exhibited the best performance, indicating better OER activities in neutral to alkaline medium. The OER activities of larger δ-Fe₁₃ Keggin clusters showed reduced OER activities compared to the Fe₂ dimers and Fe₃ trimers; however, Co(III) doping enhanced the OER activity, showing an overpotential of ∼1.07 V. The better performance of the Co(III) doped Fe(III) oxyhydroxide clusters was then rationalized in terms of the stabilities of oxyl radical species centered on the Co(III) center compared to the Fe(III) center of the oxyhydroxide clusters. These findings may offer insights into optimizing Fe-oxyhydroxide catalysts from natural minerals or sustainable hydrogen production in homogeneous media.