Molybdenum disulfide (MoS₂) is widely used in energy harvesting devices due to its high carrier mobility and semiconductor properties. However, the preparation of high-quality MoS₂ still faces significant challenges. In this work, we present a one-step chemical vapor deposition method for the preparation of large-size MoS₂ nanosheets with an orientation rate of over 70%. The one-step preparation method is more cost-effective and time-efficient compared to conventional techniques. The aligned MoS₂ nanosheets demonstrate a significant capacity for charge transfer in triboelectric devices. Herein, we propose a concept of MoS₂ as the charge transport layer for nanogenerator arrays for hybrid energy harvesting and high-performance direct output. Furthermore, the current density of the device exceeds 10 A/m² under ultrasonic excitation. Consequently, this finding is anticipated to offer new insights into applications such as mechanical energy conversion and MoS₂ charge transport.

Zinc-air batteries are promising energy conversion devices with high theoretical energy density, but their practical performance is limited by the kinetically sluggish oxygen reduction reaction kinetics at the air electrode. This kinetic bottleneck stems from the inefficient mass transport and insufficient accessible active sites. In order to solve this problem, constructing porous structure at the air electrode could be an efficient strategy to improve mass transfer and expose more active sites. Herein, we successfully constructed hierarchical porous structure with mesopores and micropores in two-dimensional (2D) Fe/N-codoped carbon nanoleaves. F127 micelles on the surface were introduced for the formation of mesopores, while microporous structure came from 2D Fe-doped Zeolitic Imidazolate Framework-L (ZIF-L) precursors. After pyrolysis in Ar, the derived 2D meso/microporous Fe/N-codoped carbon nanoleaves possess atomically dispersed Fe-N_x sites. Kinetic experiments demonstrate that the hierarchical porous structure reduces the mass transfer resistance. Furthermore, density functional theory calculations reveal that the Fe-N_x active sites with concave curvature within the hierarchical porous structure can lower the *OH binding energy, thereby enhancing the oxygen reduction reaction activity. The nanostructure-engineered fabrication of this hierarchical porous structure is critical for accelerating mass transfer, ultimately maximizing the efficiency of active sites.

Potassium-ion batteries are currently garnering extensive focus on account of the cost-effectiveness and generous supply of potassium resources. Investigating outstanding electrode materials that exhibit favorable performance is essential for the advancement of these batteries. Layered transition metal oxides have emerged as a highly promising cathode material owing to their high capacity and facile synthesis. However, their effective application is hindered due to inadequate performance, which can be ascribed to irreversible phase transition, air instability and interfacial instability. Herein, this review comprehensively outlines the causes of these three key scientific issues and proposes some corresponding optimization strategies, mainly including element doping, surface modification, structural design, and electrolyte optimization, with the aim of offering insights for the prospective advancement of potassium-based layered oxide cathode materials.

Proton exchange membranes (PEMs) are critical components that influence both the performance and potential of PEM fuel cells. Recent advancements in hybrid organic-inorganic and nanostructured fillers containing membranes have improved proton conductivity, chemical stability, and mechanical durability. The integration of advanced nanomaterials has enhanced dimensional stability and reduced fuel crossover, while emerging polymer chemistries offer superior electrochemical stability and conductivity. High-temperature PEMs have demonstrated excellent stability at elevated temperatures. System innovations, including optimized flow field designs, have further addressed mass transfer and water management challenges, enhancing overall fuel cell performance and longevity. Additionally, life cycle assessments and techno-economic analyses have provided insights into the environmental and economic impacts of PEM fabrication. While challenges remain in balancing performance, cost, and scalability, ongoing interdisciplinary research in material science and fuel cell engineering continues to drive improvements, supporting the broader adoption of fuel cells in sustainable energy systems.

Ramsdellite MnO₂ (R-MnO₂), with its expanded (1 × 2) tunnels, offers superior Zn²⁺ diffusion kinetics for aqueous zinc-ion batteries but suffers from metastability-induced phase collapse. Herein, Fe³⁺ doping is demonstrated as a critical strategy to thermodynamically stabilize R-MnO₂ while optimizing its electrochemical functionality. Through a synergistic H⁺/Fe³⁺ hydrothermal process, spent ZnMn₂O₄ from alkaline batteries is converted into orthorhombic R-Fe_xMn_1-xO₂ nanocrystals. Fe³⁺ incorporation enlarges the tunnel structure, reduces surface energy, and mitigates Jahn-Teller distortion by increasing the Mn⁴⁺/Mn³⁺ ratio. This yields a high specific surface area, enhanced ion diffusion kinetics, and exceptional cycling stability. The R-Fe_xMn_1-xO₂ cathode achieves a 286.8 mAh g^-1 capacity at 0.1 A g^-1, outperforming β-MnO₂ (30.9 mAh g^-1 at 1.5 A g^-1). This work establishes Fe³⁺ doping as an essential mechanism for stabilizing high-performance metastable cathodes, enabling sustainable upcycling of battery waste.

The use of highly concentrated electrolytes to enlarge the operational electrochemical window of MXenes is a strategy to enhance their energy density. Here, we demonstrate that V$ _4 $C$ _3 $T$ _z $ can operate in a -0.7 to 0.8 V vs. Ag electrochemical window in a 17.5 m LiBr/H$ _2 $O electrolyte achieving a high capacity/capacitance of 237.1 C g^-1/745.5 C cm^-3/158 F g^-1, electrode energy density of 49.4 Wh kg^-1/155.3 mWh cm^-3, and a high cycling stability up to 10, 000 cycles. This performance is superior to previously reported MXenes, including Ti$ _3 $C$ _2 $T$ _z $ and Ti$ _2 $CT$ _z $ tested in water-in-salt electrolytes and hydrate melts. We demonstrate the key role of electrolyte concentration in maximizing the electrochemically stable window. Electrolyte formulations in the low-concentration (5 m, 7.5 m and 10 m) and high-concentration (12.5 m, 15 m, 17.5 m, and 19 m) regimes were investigated. The best performance balance of capacity, capacity retention, Coulombic efficiency and cycling stability was achieved in the 17.5 m electrolyte. Electrochemical methods showed that this electrolyte formulation enabled the stabilization of the electrode against the hydrogen evolution reaction and oxidation processes at negative and positive potentials vs. Ag, respectively, where an interfacial film at the electrode-electrolyte interface, confirmed by electrochemical impedance spectroscopy, played a key role. Physical properties of the electrolyte were correlated to electrode performance. Importantly, this optimum performance was achieved without reaching the electrolyte concentration at the LiBr solubility limit at room temperature (19 m), which undermines rate performance and brings other operational issues.

The oxygen evolution reaction (OER), as a pivotal process in electrochemical water splitting, directly determines energy conversion efficiency. Ruthenium (Ru)-based catalysts have gained considerable attention in recent years due to their decent intrinsic activity in acidic media. Previous studies have demonstrated that while Ru exhibits superior OER activity compared to RuO₂ in acidic environments, its operational stability remains markedly inferior. This performance dichotomy, coupled with the persistent challenges of active species dissolution and catalyst particle aggregation during prolonged operation, significantly hinders their practical implementation in electrochemical systems. To address these challenges, this study develops a carbon nanotube (CNT)/Fe-Ni@RuO₂@PANI-350 composite catalyst composed of RuO₂ nanoparticles supported on bimetallic Fe-Ni modified CNTs (CNT/Fe-Ni) and encapsulated with polyaniline (PANI). This catalyst utilizes the anchoring effect of bimetallic Fe-Ni sites and the spatial confinement effect of PANI coating layer, effectively inhibiting the dissolution and agglomeration of RuO₂ during both high-temperature processing and electrochemical operation, thereby significantly enhancing electrochemical stability. The anchoring strength of RuO₂ nanoparticles on CNT/Fe-Ni support via the nano-confinement effect, as well as the microscopic mechanisms underlying the performance enhancement, are revealed by density functional theory calculations and experimental characterizations. The composite catalyst demonstrates fascinating OER performance in 0.5 M H₂SO₄, exhibiting a low Tafel slope of 39.1 mV dec^-1 as well as low overpotentials of 188 and 225 mV at current densities of 10 and 100 mA cm^-2, respectively. Remarkably, the composite catalyst demonstrates significantly enhanced stability, exhibiting only ~30 mV overpotential increase during 150 h continuous operation at 10 mA cm^-2. This study highlights a simple yet effective nano-confinement strategy to address the challenges of Ru-based catalysts, and provides a practical paradigm for designing and preparing highly efficient OER electrocatalysts with enhanced stability.

This study addresses a key research gap in proton exchange membrane fuel cell development by first establishing a pre-optimized non-graded catalyst layer as a reference, enabling a clearer understanding of performance improvements achieved through structural optimization. The reference catalyst layer was tuned for ionomer content and distribution, providing a high-performing baseline. Building on this, we systematically introduced through-plane gradients in Pt/C loading, ionomer-to-carbon ratio, and ionomer equivalent weight, both individually and in combination. Electrochemical impedance spectroscopy was used to unravel the underlying transport and kinetic effects. The fully graded catalyst showed a 32% performance increase at 0.6 V (humid conditions) and a 17% gain at 0.6 V (dry conditions) compared to the pre-optimized reference. These gains result from improved catalyst utilization near the membrane, enhanced gas diffusion and water management near the gas diffusion layer, and balanced ionic conductivity across the catalyst layer. The findings highlight the critical importance of combining a robust baseline optimization with rational gradient design, offering a comprehensive path to improve performance while minimizing precious metal usage. While structural factors are known to influence catalyst layer performance, this study focuses specifically on electrochemical behavior to provide detailed insights into compositional gradient effects.

The increasing prevalence of portable electronics and Internet of Things devices has led to a rising demand for energy storage devices that can charge and discharge quickly. Supercapacitors, known for their high power density and long working life, are considered as promising candidates. Nevertheless, the comparatively low energy density continues to pose a substantial challenge. Activated carbon, despite its widespread use as the electrode material, still suffers from unsatisfactory specific volumetric capacitance. Here, we propose a novel co-chemical welding strategy using coal liquefaction residue-derived carbon dots and melamine as precursors, developing a nitrogen/oxygen-codoped dense porous carbon with carbon dot-embedded amorphous carbon structure via electrostatic assembly and mechanical compaction. The optimized material achieves a high compaction density of 1.19 g cm^-3, providing continuous conductive pathways and additional active sites due to nitrogen/oxygen (N/O) co-doping. Our experimental results demonstrate remarkable improvements in both volumetric and gravimetric specific capacitances, reaching 373.6 F cm^-3 and 314 F g^-1 at a current density of 1 A g^-1, respectively. Density functional theory results also confirm that N/O co-doping enhances ion adsorption capacity. This study may provide a new approach for developing high-volumetric capacitance supercapacitor electrode materials, thereby advancing the field of energy storage technologies.

Conductive hydrogels have emerged as crucial components for sophisticated flexible energy storage devices, such as batteries and supercapacitors, because of their customizable microstructures, mechanical versatility, and integrated electronic/ionic conductivity. Conventional fabrication methods face persistent challenges in balancing electrical performance with mechanical durability and constructing complex three-dimensional (3D) geometries. Three-dimensional-Printed addresses these limitations by enabling precise spatial control over material deposition and structural design. This review comprehensively analyses three critical aspects of 3D-printed conductive hydrogels: (1) Fundamental conduction mechanisms in electronic, ionic, and composite hydrogels, focusing on material optimization through nanoscale dispersion control and dynamic network design; (2) Advanced manufacturing methods including photopolymerization and direct ink writing, analyzing critical parameters including rheological behavior, printing resolution, and structural-functional synergy; (3) Groundbreaking applications in flexible energy storage, particularly supercapacitors with geometrically enhanced electrodes and batteries featuring self-healing zinc anodes. Persistent challenges in material compatibility, scalability trade-offs between resolution and speed, and interfacial stability are critically assessed. Future research directions focus on multifunctional ink development, multiscale structural engineering, and reliability optimization to enable customized, commercially viable flexible energy storage technologies.