ACS Materials Letters最新文献

Ammonia has received considerable attention as a promising carbon-free hydrogen carrier. At temperatures above 400 °C, NH₃ is thermodynamically unstable with respect to decomposition into nitrogen and hydrogen and is, thus, suitable for direct use in solid oxide fuel cells (SOFCs) without external reforming. However, poor catalytic activity for ammonia decomposition at the moderate temperatures of protonic ceramic fuel cell (PCFC) operation has resulted in low fuel cell power output relative to operation on hydrogen and likely contributes to reported cell degradation. Here we prepared cells based on a thermodynamically robust electrolyte, a high activity cathode, and an anode with a distinctive structure to overcome challenges of poor activity and stability. The cells delivered peak power densities of 0.59 and 0.44 W cm^–2 under H₂ and NH₃, respectively, at 500 °C, excellent stability over a period of 200 h, and no detectable NO_x in the anode exhaust gas.

Prussian White (PW) is a strategic cathode material for sodium-ion batteries, offering a high theoretical capacity and voltage. However, the crystalline structure and the electrochemical performance of PW strongly depend on the hydration level, which is difficult to control, leading to discrepancies in the results and interpretations presented in the literature. This work aims to provide a deeper insight into the dehydration process of PW materials and a better understanding of the impact of their fast rehydration, upon exposure to moisture, on their characterization. For this purpose, a Na_1.87Mn[Fe(CN)₆]_0.99·1.99H₂O sample was synthesized by a coprecipitation method and subsequently dehydrated to remove water. After thorough characterization, our findings show that drying parameters, such as temperature and pressure, strongly influence the post-drying result. Moreover, the dehydrated samples rehydrate within minutes of exposure to air, which may explain some discrepancies observed in the literature and highlights the necessity to work under fully air-tight conditions.

All-solid-state lithium batteries (ASSLBs) with Ni-rich cathodes are promising candidates for achieving high energy and improved safety. However, their electrochemical performance is limited by cathode loading, especially in the absence of conductive agents. Herein, we utilize electronically conductive Li-deficient LiNiO₂ (LD-LNO) to construct high-areal-capacity ASSLBs under high cathode loading. This LD-LNO shows an inherent enhanced electronic conductivity and minimal surface impurities. Electrochemical analysis combined with solid-state nuclear magnetic resonance spectroscopy demonstrates the mitigation of the detrimental H3 phase transition and the side reactions at the LD-LNO/Li₆PS₅Cl interface. As a result, LD-LNO-based ASSLBs achieve competitive cyclability and rate capability without the need for cathode modifications. A high reversible areal capacity of 15.2 mAh cm^–2 is attained at 35 °C under a 133.8 mg cm^–2 LD-LNO mass loading. This work sheds light on electronically conductive cathodes, providing a perspective for addressing the high cathode loading issue in ASSLBs.

Narrow-bandgap (NBG) perovskite solar cells based on tin-lead mixed perovskite absorbers suffer from significant open-circuit voltage (V _OC) losses due primarily to a high defect density and charge carrier recombination at the device interfaces. In this study, the V _OC losses in NBG perovskite single junction cells (E _g = 1.21 eV) are addressed. The optimized NBG subcell is then used to fabricate highly efficient all-perovskite tandem solar cells (TSCs). The improvement in the V _OC is achieved via the addition of a thin poly(triarylamine) interlayer between the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)-based hole transport layer (HTL) and the NBG perovskite. The optimal bilayer HTL results in a champion power conversion efficiency (PCE) of 20.3%, compared to 17.8% of the PEDOT:PSS-based control device. The V _OC improvement of the single-junction NBG cell is also successfully transferred to all-perovskite TSC, resulting in a high V _OC of 2.00 V and a PCE of 25.1%.

This study proposes a steric hindrance-derived electrolyte (STE) to generate Li⁺ anion-rich solvation structures to enhance the Li-mediated nitrogen reduction reaction (Li-NRR), a promising electrochemical green ammonia synthesis method. The STE applied methylation of the alpha proton in the tetrahydrofuran (THF) solvent, which dissolved lithium salts, leading to the weak solvation of Li⁺ and generating an anion-rich-solvated structure. The resultant anion-derived solid electrolyte interphase with thin and uniform inorganic properties improved the selectivity, energy efficiency (EE), and stability of the Li-NRR process. Additionally, the anion-rich solvation exhibited antireduction stability and inhibited electrolyte decomposition. Consequently, the STE achieved a 2-fold increase in Faradaic efficiency and NH₃ yield rate (65.8% and 90.8 nmol cm^–2 s^–1, respectively) compared to the THF-single electrolyte (35.7% and 49.3 nmol cm^–2 s^–1) while increasing the EE by 1.5 times.

Urgent demand for a sustainable power supply for wearables promotes great efforts on the development of flexible thermoelectric devices. The elastic bendability allows the reservation of initial power and flexibility in inorganic thermoelectric films. The elasticity is related to the thickness engineeringly and the elastic strain scientifically, therefore guiding this work to focus on developing elastic thermoelectric generators using high-performing orthorhombic Ag₂Se_1–xS_x films that thinned the bulks through multipass hot-rolling at ∼393 K. Such a plastic deformation enables a creation of dense dislocations and a refinement of grain and, thereby, a dramatic increase in the elastic strain, impressively securing a full recoverability in transport properties for the obtained films even after 100,000 times bending within a radius down to ∼3 mm. The resultant achievement of extraordinary specific power density of ∼5 μW/cm-K² in a six-leg flexible device robustly demonstrates these alloys as a potentially sustainable power source for wearable electronics.

Elucidating and regulating dynamic catalyst reconstruction are crucial for various electrocatalytic reactions. Here, we applied model fittings with operando characterizations to quantify the reconstruction activity (i.e., ability to reconstruct) of layered Co(OH)₂ toward the oxygen evolution reaction (OER). By modulating the intercalation species into Co(OH)₂, we governed distinct reconstruction thermodynamics and kinetics, with diverse mass changes and heterogeneous Co oxidation during the OER. We further established a volcano-type relationship between reconstruction activity and OER activity and identified that a moderate reconstruction activity, achieved by dual-anion intercalation, favored a high OER activity. This might result from its proper basal spacing that regulated the coupled ion (de)intercalation–electron transfer for reconstruction, leading to optimal Co for binding OER intermediates. The optimally reconstructed Co(OH)_1.26Cl_0.08(CO₃)_0.33·0.84 H₂O delivered 1 A cm^–2 at 1.78 V for anion-exchange membrane water electrolysis. This work laid the foundation for modulating reconstruction activities to benefit electrocatalysis.

Layered vanadium-based materials have been extensively studied as promising cathode materials for aqueous zinc-ion batteries (AZIBs). However, challenges remain to achieve the desired high energy conversion efficiency and energy densities as well as long cycling stability requiring an in-depth understanding of the local and the electronic structure of a vanadium-based cathode, especially concerning the impacts on electrochemical potential and mass transfer in the electrochemical process. In this work, 1-butyl-1-methylpyrrolidinium cations are preintercalated into the layered hydrate vanadium pentoxide (V₂O₅·nH₂O) and partially replace the electroneutral structural water, changing the local atomic environment. X-ray absorption spectroscopies demonstrate the V–O bond elongation and the distortion in the [VO₆] octahedra, which alter the ligand field and brings the V 3d state to a lower energy level, ultimately leading to an increase in the electrochemical potential. It is also revealed that the preintercalated organic cations exert electrostatic interaction with lattice oxygen, stabilizing the layered structure and buffering lattice strain during cycling. Consequently, the modified cathode achieves a superior specific capacity of 412 mAh/g at 0.5 A/g and a capacity retention of 97% after 3000 cycles at 8 A/g. The unveiled correlation between local structure and electrochemical performance paves the way for optimizing the cathode materials by manipulating the local coordination environment.

Low-cost cathode materials with high energy density and good rate performance are critical for the development of next-generation solid-state Li-ion batteries (SSLIBs). Here, we report Li₂FeCl₄ as a cathode material for SSLIBs with highly reversible Li intercalation and deintercalation, a high operation voltage of 3.7 V vs Li⁺/Li, good rate capability, and good cycling stability with an 86% capacity retention after 6000 cycles. Operando synchrotron XRD reveals that the phase evolution of Li₂FeCl₄ during charge–discharge cycling involves both solid-solution and two-phase reactions, which maintains a very stable framework during Li insertion and extraction.

Molecular materials with high structure-design freedom are used as new interface passivators to reduce nonradiative recombination in inverted perovskite solar cells (PSCs). However, most molecular modifiers are unable to achieve a long-term passivation effect due to self-aggregation. Here, the molecular modifier 1-methyl-2-thiomethyl-1H-imidazole-5-carboxylate (SMC) with ester and thiol groups is carefully developed. The ester groups weaken self-aggregation triggered by intermolecular hydrogen bonds, making such aggregations easier to disassemble during heating to form a net-like insulating layer with random openings, which dramatically increase charge transport. More importantly, the electron transfer between thiol and disulfide can accelerate the elimination of Pb₀ and I₂ by redox reactions to prevent phase separation. Ultimately, the optimized inverted PSCs with bandgaps of 1.68 and 1.55 eV showed surprising fill factors of 84.83% and 86.18%, resulting in champion efficiencies of 23.45% (certified 22.98%, which is the highest to date for wide-bandgap) and 25.71% (certified 25.28%), respectively. Remarkably, both unencapsulated devices maintained over 94% of their initial efficiency under maximum power point tracking for 600 h (50 °C) and 1000 h (65 °C), respectively, confirming impressive long-term operational stability.