ACS Applied Energy Materials最新文献

Conventional lithium-ion batteries employing thin electrodes are approaching their energy density limits. Thick electrode technology represents a promising solution by increasing mass loading while maintaining efficiency and cost-effectiveness. However, they suffer from a severe ionic transport bottleneck due to elongated and tortuous ion diffusion pathways, which hinder their practical application. In this work, we present a template-free strategy for fabricating low-tortuosity thick LiCoO₂ (LCO) electrodes (denoted as A-LCO and S-LCO) with 40 mg cm^–2 active material mass loading, and using NH₄HCO₃ and NaHCO₃ as foaming agents, respectively. The resulting porous structure electrodes exhibit substantial improvements over conventional plate electrodes (C-LCO), with A-LCO showing superior performance due to the facile decomposition of NH₄HCO₃. A-LCO delivers a specific capacity of 74.5 mAh g^–1 at 2C, in stark contrast to the nearly negligible capacity of 0.2 mAh g^–1 for C-LCO. The enhanced performance of A-LCO is attributed to optimized ion transport (with tortuosity reduced from 20.35 to 10.92), improved electrolyte wettability (contact angle decreased from 28.624° to 8.706°), and more uniform Li⁺ distribution (concentration gradient reduced by 69%). By regulating the ion transport paths through rational structural design to address the fundamental ionic transport bottleneck, this approach offers a promising pathway toward high-energy-density batteries without compromising rate capability or cycling stability.

Alkaline ion-solvating membranes (ISMs) combine the high conductivity of aqueous hydroxide solutions with the gas barrier properties of dense polymer films and are, therefore, an attractive class of electrode separators for alkaline water electrolysis. The absence of intrinsically unstable cationic groups in these membranes broadens the scope of polymer chemistries that can be used compared with conventional anion exchange membranes. Exceptional cell performance has been reported with polybenzimidazole-based ISM, but the lifetime is limited due to polymer degradation through polymer chain scission. This work reports the synthesis and characterization of N-functionalized poly(biphenyl piperidine) (PBP)-based ISM. PBP has a full hydrocarbon backbone and has gained a lot of attention in the anion exchange membrane community due to its excellent alkaline stability. The pristine poly(biphenyl piperidine) is highly hydrophobic, and the electrolyte uptake is, therefore, low. To promote electrolyte uptake and to enhance conductivity, the piperidine moieties were functionalized with four different polar pendant groups via N-substitution, containing alcohol, primary amine, carboxylate, and sulfonate functionalities. The former two, which are not charged in the pH range investigated, were found to bring about negligible changes in electrolyte uptake and other key properties. The membranes functionalized with anionic moieties (carboxylate and sulfonate), on the other hand, allowed the increase of KOH electrolyte uptake to above 50%, and proved to be suitable for water electrolysis applications.

In this study, a phosphide-functionalized interfacial layer was constructed on a 3D carbon-coated Co-modified copper current collector (Cu@C–Co) via a vapor-phase deposition technique, yielding a multifunctional Cu@C–Co–P architecture. This rational design synergistically integrates the high specific surface area of the hierarchical porous structure with the strong lithiophilicity of Cu₃P, significantly reducing the lithium nucleation overpotential and enabling spatially confined lithium deposition within the 3D conductive framework. During cycling, an in situ-formed Li₃P interphase with excellent ionic conductivity and mechanical robustness effectively suppresses dendritic growth and interfacial side reactions. Electrochemical evaluations demonstrate that the symmetric cells based on Cu@C–Co–P exhibit ultrastable cycling over 2600 h at 1 mA cm^–2, while full cells maintain ∼90% capacity retention after 160 cycles at a high rate of 5 C. Moreover, the lithium-ion diffusion coefficient is enhanced by more than 28%. This work provides a multifunctional current collector design that simultaneously enables guided lithium deposition, interfacial stabilization, and fast ion transport, offering a promising pathway toward high-energy-density lithium metal batteries.

Lowering the iridium content in the anodic catalyst layer remains one of the main challenges for proton exchange membrane water electrolysis (PEM-WE), as it can cause discontinuous catalyst layers and increased overpotentials. In this work, we managed to reproducibly cast anodic catalyst layers with a loading as low as 22 μg_Ir/cm² by introducing electrospun antimony-doped tin oxide (ATO) nanofibers along the IrOx nanoparticles. In addition to a facilitated fabrication route for low-loaded catalyst layers via casting, electrolyzer cells with these ATO-supported catalyst layers reached a loading-normalized current of 454 A/mg_Ir at their maximum operating point, which is almost four times higher than the reference cells (120 A/mg_Ir) with a loading of 100 μg_Ir/cm².

We use a combination of experiments and coarse-grained molecular dynamics simulations to elucidate the structure–property relationships in polymer electrolytes obtained by the copolymerization of poly(vinyl ethylene carbonate─lithium styrene bis(trifluoromethanesulfonyl)imide) or p(VEC-LiSTFSI). Experiments show that the conductivity reduces with increasing anion (i.e., STFSI) fraction on the chain, and the cation transference number (t₊) is found to be dependent on the anion fraction. Furthermore, a significant fraction of unpolymerized VEC monomers are observed. Since it is inherently difficult to experimentally control the chain architecture and the amount of unpolymerized VEC in these systems, we perform coarse-grained molecular dynamics simulations on model polymer systems with different chain architectures to mimic the plausible experimental systems. Specifically, we look at the differences in transference numbers arising from (i) a random copolymer of VEC and STFSI monomers; (ii) a blend of VEC-STFSI copolymer with VEC monomers; and (iii) a ternary blend of the VEC homopolymer, STFSI homopolymers, and VEC monomers. The ternary blend model demonstrates the closest resemblance with the experimental transference numbers and diffusivities. The lithium diffusivity obtained from the coarse-grained models with VEC monomers (plasticizers) is about 1.5 times that of the model without VEC monomers, showing that the plasticizing effect of VEC monomers is modest. We rationalize the experimental observations based on aggregate and cluster analyses obtained from molecular simulations. This work reveals that polymer electrolyte chain architecture and plasticizers can critically influence the transport properties, and these parameters should be considered when designing single ion conducting polymeric electrolytes.

Developing robust, high-performance electrochemical catalysts for hydrogen production from natural seawater or alkaline freshwater presents a significant challenge. Herein, we report an electrocatalyst system of AuCu bimetallic nanoparticles (NPs) supported on 1T-MoS₂ (AuCu/1T-MoS₂) synthesized via hydrothermal/solvothermal methods followed by controlled electrochemical deposition. Experimental electrochemical measurements combined with density functional theory (DFT) calculations reveal that the AuCu/1T-MoS₂ catalyst exhibits superior hydrogen evolution reaction (HER) activity in alkaline freshwater compared with natural seawater. DFT indicates that adsorption of Na⁺ or Cl^– on the active Au sites makes the Gibbs free energy of hydrogen adsorption (ΔG_H) more negative, thereby disfavoring H₂ desorption and reducing activity in seawater. Experimentally and theoretically, the introduction of AuCu NPs increases the density of accessible active sites by activating the otherwise inert basal planes of 1T-MoS₂. The Cu component facilitates water dissociation and lowers ΔG_H, while Au improves the electrical conductivity. The orbital hybridization between the d states of AuCu and those of Mo in 1T-MoS₂ results in a higher density of states at the Fermi level, thereby improving conductivity and reducing ΔG_H. Charge redistribution at the AuCu/1T-MoS₂ interface produces a synergistic enhancement of HER kinetics. Our findings offer design principles for bimetallic/2D hybrid electrocatalysts tailored for seawater and alkaline electrolysis.

Hematite (α-Fe₂O₃) is a promising semiconductor for photoelectrochemical (PEC) water splitting because of its favorable band gap. However, the challenge of improving PEC performance by constructing effective and stable cocatalysts on the surface of α-Fe₂O₃ persists. This study presents a simple approach for fabricating active α-Fe₂O₃ photoanodes coated with cerium-doped metal–organic framework (MOF) films. By adjustment of the Fe and Ce compositions of the MOFs, it was feasible to enhance the band gaps and band positions of the α-Fe₂O₃/MOF heterojunction. X-ray absorption spectroscopy (Fe K-edge XANES and EXAFS and Ce L₃-edge XANES), along with X-ray photoelectron spectroscopy, was employed to investigate the oxidation states of Fe and Ce, as well as their local structural environments in the MOF, providing insights into the enhanced water oxidation performance. The α-Fe₂O₃/MIL-53(Fe): x Ce thin film exhibited a photocurrent density of 2.3 mA cm^–2 at 1.23 V vs RHE, up to four times that of the pristine α-Fe₂O₃ photoanode. The MIL-53(Fe) catalyst, loaded with 2.7% Ce, exhibits enhanced PEC activity, relating to the reduced recombination of photogenerated carriers, increased active sites, and improved charge separation and transfer efficiency. This study offers novel views of the advancement of MOF-based composites for PEC water oxidation.

The field of sensors is moving toward miniaturization, and it requires suitable power sources for operation. In this context, the triboelectric nanogenerator (TENG) can become a partial solution as a sustainable power source for various sensors. The present work focuses on developing a TENG fabricated from the flexible polymer-ceramic composite films, i.e., PDMS-Bi_0.5(Na_1–xK_x)_0.5TiO₃ where x = 0.1, 0.14, 0.18, and 0.22 (BNT-BKT), which act as potential self-powering devices for sleep and respiration monitoring. The structural and spectroscopic characterization of the BNT-BKT particles showcased the presence of a morphotropic phase boundary. The dielectric constant increases with the inclusion of BKT, and the observed dielectric loss of the BNT-BKT samples is much less compared to that of the parent BNT samples. An attempt is made to fabricate a TENG based on PDMS/BNT-BKT composites (CFs). The triboelectric nanogenerator with 10 wt % PDMS/BNT-BKT CF gives an electrical output voltage of 292 V and a current of 3.47 μA. Finally, a calculator is successfully powered by charging a 47 μF capacitor using the fabricated TENG device. Furthermore, the TENG device is utilized for continuous monitoring of breathing patterns during rapid exercise and also jerks during sleep, underscoring its wide application in healthcare monitoring.

Organic–inorganic metal halide perovskites exhibit remarkable power conversion efficiency (PCE) but face challenges in stability when exposed to environmental factors such as moisture, oxygen, heat, and light. Quasi-two-dimensional (2D) perovskites fabricated by incorporating spacer cations into 3D perovskite structures offer a promising route to enhance stability without compromising optoelectronic performance. This study introduces octylammonium (OA) as a spacer cation suitable for bulk incorporation and fabrication of quasi-2D perovskites. OA improves the stability of the perovskites due to its greater chemical inertness and by defect passivation at surfaces and grain boundaries. Crystallographic, photophysical, structural, vibrational, and morphological analyses via X-ray diffraction, ultraviolet–visible spectroscopy, steady-state/time-resolved photoluminescence, Raman spectroscopy, Fourier transform infrared spectroscopy, and field-emission scanning electron microscopy reveal that OA incorporation improves crystal orientation/size and optical absorption in films, reduces defect density, improves diffusion length, and stabilizes the perovskite lattice. Quasi-2D perovskite films with proper stoichiometry (n = 80) retain their initial optoelectronic properties longer than 3D MAPbI₃. Electrical characterizations, including J–V measurements, external quantum efficiency (EQE), and electrochemical impedance spectroscopy, demonstrated comparable PCE and EQE and enhanced recombination resistance in OA-incorporated devices. Demonstrating enhanced environmental stability, quasi-2D PSCs incorporating OA showed 43.6% better retention of the initial PCE than MAPbI₃ during accelerated aging tests. Their superior performance was further established by a 21.6% improvement in shelf stability over 3600 h. The current work underscores the potential of spacer cation engineering in advancing stable and efficient photovoltaics. It demonstrates that stable and efficient quasi-2D perovskite solar cells can be realized under ambient fabrication conditions, without requiring any kind of controlled inert environment, through OA-mediated structural stabilization, offering a practical low-cost route toward scalable device production.

Enhancing energy density is essential for the practical application of lithium–oxygen batteries. Here, we report a self-standing cathode composed of ultralong carbon nanofibers with lengths of at least several tens of micrometers and a typical diameter of 80 nm, designed to operate under lean electrolyte conditions with minimal cathode weight. The sheet, with a thickness of 0.136–0.180 mm and a weight of 2.5–2.6 mg cm^–2, consistently achieved discharge capacities exceeding 4 mAh cm^–2 at 0.1 mA cm^–2, even when the electrolyte filled only 36 vol % of its void volume. This performance corresponds to an energy density of ∼500 Wh kg^–1. Analysis of the discharge capacity and electrolyte utilization indicates that discharge proceeds via electrolyte migration within the sheet. Comparative studies with fibers of different diameters suggest that large voids naturally formed between carbon nanofibers with moderate-sized diameters play a key role in facilitating electrolyte migration.