ACS Applied Energy Materials最新文献

Degradation studies were conducted of two different membrane electrode assemblies (MEAs), containing identical cathode electrocatalysts (Pt/C) and dissimilar anode electrocatalysts (Pt/C; different carbon support). They were subjected to identical durability tests in a rarely reported ion-pair membrane-based high-temperature proton exchange membrane fuel cell (HT-PEMFC). To elucidate the degradation mechanisms, the fresh MEAs and the degraded MEAs (MEA1 and MEA2), that had undergone a durability test, were characterized with comprehensive chemical, structural, and morphological analyses. Platinum dissolution and Pt particle growth were identified as the major contributors to the electrocatalyst degradation by reduction of the electrochemical surface area. X-ray photoelectron spectroscopy measurements exhibit subtle changes in the chemical state of Pt and C, suggesting corrosion of support carbon and redeposition of Pt on ordered carbon during HT-PEMFC operation. Additionally, significant membrane thinning, more pronounced in MEA2 (∼70% reduction) than in MEA1 (∼50% reduction), was observed, which was accompanied by reduced thermal stability and integrity of the membrane. The interplay between carbon corrosion, Pt crystallite growth, and membrane degradation constituted a self-reinforcing degradation loop in the studied HT-PEMFC MEAs.

Precise compositional control of Pt-based alloys is essential for designing efficient and cost-effective electrocatalysts for direct alcohol fuel cells (DAFCs). Here, we report the synthesis of structurally uniform and composition-tunable PtCu alloy nanoclusters via cluster beam deposition using a single magnetron source. By the adjustment of the exposed Pt target area on a custom-designed sputtering ring, the Pt-to-Cu ratio was precisely controlled in a scalable manner. High-resolution electron microscopy confirmed homogeneous, size-tunable alloy clusters, while X-ray photoelectron spectroscopy revealed electron transfer from Cu to Pt, indicating electronic modification upon alloying. Theoretical calculations further support a fully miscible alloy configuration. Electrochemical measurements demonstrated that Cu incorporation significantly enhances the catalytic activity of Pt clusters for both methanol and ethanol oxidation in acidic media while reducing the Pt content. Notably, Pt₁Cu₁ nanoclusters achieved mass activities 53-fold (methanol oxidation reaction) and 14-fold (ethanol oxidation reaction) higher than commercial Pt/C, with activity exhibiting a volcano-type dependence on alloy composition. These results highlight the critical role of composition-structure tuning in dictating catalytic behavior and establish a general strategy for designing high-performance, resource-efficient bimetallic catalysts for DAFC applications.

Lattice oxygen redox (LOR) reactions in sodium-ion battery (SIB) layered oxides are considered a promising approach to overcoming capacity limitations. However, under high-voltage conditions, irreversible LOR-induced local structural distortions and phase transitions can lead to a significant degradation of electrochemical performance, limiting their practical application. In this study, Sn⁴⁺/Sb⁵⁺ were successfully introduced into layered cathode materials. It was found that Sn⁴⁺ doping maintained the ribbon-ordered superstructure of the transition metal (TMs) layers, while Sb⁵⁺ incorporation, through the formation of strong covalent Sb–O bonds, altered the ordering of the TMs layers, effectively alleviating lattice strain and suppressing structural collapse at high voltage. Moreover, the strong covalent bonds between Sb–O weakened the interaction between the O 2p orbitals and the TM 3d orbitals, activating the redox activity of lattice oxygen at high voltage and significantly improving energy density. This study proposes an effective method to enhance anionic redox activity, highlights the impact of superstructure transformations on the crystal structure and electrochemical performance, and provides fundamental mechanistic insights into element doping for anionic redox-active cathode materials.

Proton exchange membrane (PEM) electrolysis is a crucial technology for sustainable hydrogen production, yet the discovery of efficient and durable anode materials remains a challenge. In this work, literature data on PEM electrolysis are systematically collected and analyzed to identify trends in material selection, synthesis methods, and key experimental conditions. Statistical analysis revealed that a limited number of anode and cathode materials dominate the field primarily due to their catalytic activity and stability in acidic environments. Supervised machine learning is then employed to predict anode materials aimed at reducing Ir content in the anode material by using compositional and experimental descriptors to model the cell performance. Experimental validation of Ir_0.9M_0.1O₂ (M = Cr, Zn, Sb, Ho) demonstrated that incorporating these predicted elements preserved cell performance while enabling a reduction in the Ir content at the anode. This study demonstrates that integrating data-driven approaches with literature analysis can effectively guide the discovery of anode materials, advancing the PEM electrolysis technology.

An accelerated stress test (AST) is widely used to shorten the time required to assess the long-term durability of fuel-cell catalysts; however, the degradation mechanism of Pt/C under AST conditions remains poorly understood. In this study, we introduce a three-electrode in situ electrochemical cell that combines electrochemical control with multimodal X-ray measurements to clarify Pt/C cathode degradation during AST. Using a commercial Pt/C model catalyst, we conduct in situ X-ray absorption spectroscopy, X-ray diffraction, and small-angle X-ray scattering under identical conditions to monitor electronic, crystallographic, and particle-size evolution. Aggregation occurs predominantly within the first ∼500 cycles, while coalescence and Ostwald ripening are minimal. The subsequent slowdown in structural evolution is consistent with progressive Pt oxidation and passivation, which suppresses further growth. Periodic cleaning during AST removes surface oxides and leads to more pronounced degradation. These findings highlight the importance of precision AST designs that explicitly consider early-stage aggregation and later-stage passivation while maintaining a sufficiently reducing environment to ensure meaningful acceleration.

Zinc oxide has been extensively studied for its photocatalytic and photoelectrocatalytic applications due to its wide-bandgap (3.37 eV) and strong response to ultraviolet (UV) light. However, its practical application is hindered by intrinsic limitations such as poor visible light absorption, poor electrical conductivity, rapid charge carrier recombination, and environmental photocorrosion. The synthesis of these carbon-coated ZnO nanospheres via laser ablation of ZnO nanorods presents an approach for enhancing photoelectrocatalytic performance. In this study, ZnO nanorods were first synthesized via a reflux method and subsequently subjected to laser ablation mixed with a carbon precursor, leading to the formation of these carbon-coated ZnO nanospheres. The structural, morphological, and compositional characteristics of the synthesized (ZnO@C) nanospheres were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The optical response in the UV–vis shows an appreciable increase in the absorbance for the sample after carbon coating on ZnO. To validate the observation, an finite-difference time-domain (FDTD) simulation was carried out, showing a notable increase in absorption intensity (∼84%) compared to pristine ZnO. In electrochemical tests, the thin carbon coating reduces the overpotential for the hydrogen evolution reaction (HER) and leads to a 5-fold increase in photocurrent under illumination, highlighting enhanced photoresponse through improved charge separation and transport. The Faradaic efficiency of hydrogen production of the composite increased to 69.4% under light irradiation compared to 41.6% in dark conditions, demonstrating the superior catalytic efficiency of the ZnO@C composite in light. The carbon coating improves electrical conductivity, effectively reducing charge recombination losses, provides structural stability, protects the ZnO from environmental degradation, and enhances electrode longevity. This work demonstrates that laser ablation provides a facile and effective strategy for advanced nanostructures, opening possibilities for advanced energy and environmental applications.

Lithium–oxygen (Li–O₂) batteries (LOBs) exhibit the highest theoretical specific energy density (∼3500 Ah kg^–1), making them an ideal next-generation energy storage system with the potential to surpass the limits of conventional Li–ion batteries in both energy capacity and gravimetric performance. However, LOBs suffer from large discharge–charge polarization and limited durability because of insulating Li₂O₂ formation and excessively strong or weak oxygenated intermediate binding with the cathode. Ruthenium-based catalysts play an important role as cathode electrocatalysts in LOBs, owing to their outstanding bifunctional activity for oxygen reduction and evolution reactions, high electrical conductivity, and tunable surface electronic structure, which enable efficient Li₂O₂ formation and decomposition. This review proposes a unifying electronic structure framework for Ru-based electrocatalysts in which the d-band center (ε_d) governs oxygen intermediate (O₂^–/LiO₂) adsorption and Li₂O₂ nucleation, morphology, and reversibility. We present d-band center engineering strategies for enhancing the oxygen electrode catalysis performance of LOBs across five strategies: oxygen vacancy engineering, alloying, heteroatom doping, coordination environment control, and heterostructure formation. We next discuss how ε_d upshift and downshift influence the oxygen intermediate binding strength and Li₂O₂ formation. Finally, we provide our perspective on the direction of Ru-based oxygen electrocatalysts for LOBs.

Hybrid perovskite materials hold significant promise for photovoltaic and optoelectronic applications, but their limited stability under ambient conditions poses a barrier to commercialization. This study systematically investigates the microstructural and optoelectronic changes due to varying concentrations of monovalent and divalent organic spacer cations butylammonium iodide (BAI) and ethane-1,2-diammonium iodide (EDI) in two-dimensional (2D) perovskite layers deposited on three-dimensional (3D) perovskite films. Grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements showed that incorporation of small amounts of BAI (0.191 wt %) into the EDI/BAI mixture significantly suppressed the residual PbI₂, promoting vertically oriented layered perovskite phases. Higher BAI concentrations (1.25 wt %) promoted dominant vertically stacked 2D phases but also induced undesirable hexagonal nonperovskite formations. GIWAXS analysis confirmed a stabilizing minor n = 2 phase driven by EDI²⁺/BA⁺ coulombic and hydrogen-bonding interactions, enabling defect passivation, reduced ion migration, and a coherent vertically oriented interface. Using Photoluminescence, UV–vis spectroscopy, and scanning electron microscopy (SEM), we observed that a 1:1 molar ratio of EDI to BAI leads to improved film morphology, enhanced optical characteristics, and greater environmental stability (consistent with improved crystallinity) compared to pure 3D perovskite films and other ligand ratios. SEM analysis correlated optimized grain structures and reduced defects with improved performance and stability. Notably, films with equal ligand ratios exhibited superior defect passivation, sustained crystallinity, and improved UV–vis absorbance after extended storage in air (up to 3.5 months). These findings provide essential insights for dimensional engineering strategies aimed at improving the performance and durability of mixed-dimensional perovskite optoelectronic devices.

Developing high-performance and affordable silicon (Si) anodes to replace graphite for large-scale deployment remains a significant challenge. Advancing silicon anodes requires not only mitigating volume expansion, a commonly encountered issue during lithiation, but also incorporating a durable, conductive, and inert coating to protect silicon from the electrolyte. In this context, a cost-effective, high-performance hollow porous silicon with an in situ carbon coating anode (HPSi@C) for lithium-ion batteries was synthesized from low-cost coal fly ash (CFA), a major industrial waste product. The hollow, porous spherical structure of silicon is inherited from the CFA bead via a simple magnesiothermic reduction. The structure enables the Si anode to expand and contract without collapsing over repeated charge/discharge cycles. In addition, the in situ carbon coating forms a stable solid electrolyte interphase, ensuring that the composite maintains its structural stability. This rational design yields an impressive initial charging capacity of 2493.3 mAh g^–1 at 100 mA g^–1, along with a first Coulombic efficiency of 82.6%. The composite also delivers a capacity of 1109.4 mAh g^–1 at a high current density of 5000 mA g^–1, demonstrating an excellent rate performance.

Catalytic doping is considered one of the most efficient strategies to achieve superior performance of MgH₂, as rationally designed catalytic components can exhibit synergistic effects, thereby optimizing the kinetic pathways. In this study, the hydrothermal method was adopted to prepare clustered Ni–Mo–S catalysts, which were used to modify MgH₂ to enhance its kinetic performance. Experimental results demonstrate that the molar proportion of Ni to Mo significantly impacts the modification effect of Ni–Mo–S catalysts on MgH₂. Furthermore, the catalyst whose molar ratio of Ni/Mo is 7:2 achieves the optimal catalytic efficiency. Specifically, at 125 °C, MgH₂-5 wt % Ni–Mo–S can absorb 4.61 wt % H₂ in 1200 s. At a relatively low temperature of 250 °C, it manifests a rapid dehydrogenation rate and releases 5.81 wt % H₂ in 2000 s. The hydrogenation (41.98 kJ/mol) and dehydrogenation (86.41 kJ/mol) activation energies of MgH₂-5 wt % Ni–Mo–S are reduced by 48.87 and 43.79% compared to as-milled MgH₂, respectively. Mechanism analysis suggests that this improvement may be ascribed to the following reasons: (1) The hydrogen pump effect of Mg₂Ni/Mg₂NiH₄ facilitates the hydrogen diffusion; (2) electron transfer between Mo species with different valence states weakens the Mg–H bonds; (3) the in situ formed MgS serves as diffusion channels for hydrogen atoms, expediting hydrogen transport. This work provides a valuable outlook for constructing highly active catalysts for MgH₂ hydrogen storage.