ACS Applied Energy Materials最新文献

Since the advent of 2D hybrid perovskites for optoelectronic devices, achieving significant out-of-plane charge transport and strong organic–inorganic orbital coupling has been a major challenge. Recent research has focused on the incorporation of polycyclic amine-based spacer cations to address this issue. In this study, we used density functional theory to explore the pressure tunability of perovskite electronic structures. Applying external pressure to naphthalene-based spacer cation-containing 2D perovskites, specifically (NaphDA)PbI₄, resulted in significantly enhanced out-of-plane carrier transport, with a hole effective mass approaching 0.16 m₀. Additionally, for another perovskite, we noticed significant inorganic–organic orbital overlap at the band edges. We discovered that the direction of applied pressure alters the intramolecular band alignment: a material with a type I_a alignment can shift to a type II_a alignment under pressure.

With growing global energy demands, the development of efficient energy storage devices like hybrid supercapacitors (HSCs) has been recognized as a viable technology, owing to their superior energy storage performance. This work demonstrated the binder-free electrodeposition synthesis of ternary Co₉S₈/NiS₂/Cu₂S (CNCS) on Ni foam through cyclic voltammetry (CV) and chronoamperometry (CA) deposition modes for HSC applications. The electrochemical outcomes indicated that the CNCS electrode prepared via the CA mode exhibited enhanced electrochemical activity compared with the CV mode. Specifically, the CA-deposited CNCS electrode demonstrated a notable specific capacity of 460.15 C g^–1 at 1 A g^–1, remarkable rate capability, and low resistance. The charge storage mechanism being majorly influenced by the diffusive controlled redox reactions as determined from Dunn’s theoretical model confirmed the battery-type features of the CNCS deposited in the CA mode. For practical utility, an HSC device CNCS(+)||activated carbon(−) was constructed that displayed a high energy density of 86.71 Wh kg^–1 and a power density of 1134 W kg^–1. This device exhibited exceptional cycling stability and maintained a capacity retention of 95.4% over 5000 cycles. The promising electrochemical performance of the CA-deposited CNCS electrode was attributed to its uniform nanosheet structure, which facilitated redox reactions and offered increased active sites for charge storage. This investigation highlights the potential of binder-less electrodeposition fabrication of ternary metal sulfides on Ni foam as an efficient electrode material for the advancement of high-performance HSCs.

The defect formation energy of perovskites is low, and ions can easily migrate and evaporate during annealing and usage. Here, we introduce 5-aminopyridine-2-carboxylic acid (5-APA) for modifying the perovskite layer to enhance the device efficiency and stability. The pyridine N and carbonyl (C═O) can form strong anchoring effects with uncoordinated Pb²⁺, effectively suppressing nonradiative recombination. Simultaneously, the amino group (−NH₂) forms hydrogen bonds with the organic cations in the perovskite film and can bind with V_MA and V_FA vacancies, thereby significantly enhancing the stability of the device. After surface modification, the crystallinity of the perovskite film was significantly improved, and the energy level alignment with C₆₀ is optimized. Specifically, the V_OC of the modified device increases from 1.09 to 1.17 V, and the PCE reaches 24.19%. After aging for 1000 h at 85 °C in a nitrogen atmosphere, the stability of the modified device remains at 81%, while the unmodified device retains only 51%. Additionally, sunlight aging in the air was simulated for 30 days. The stability of the modified device is 82%, compared to only 52% for the unmodified device. Our findings fully demonstrate the significant effect of multifunctional pyridine derivative surface modification in enhancing the efficiency and stability of perovskite solar cells.

This study explores and presents a comprehensive understanding of the synergistic effect of in situ formed TiO₂ in Ti₂C MXene (TTMXene) nanomaterials to derive enhanced energy characteristics in high-performance flexible symmetric supercapacitors. The TTMXene two-dimensional (2D) (nanocomposite) materials were synthesized by a simple single-step chemical etching method. The TTMXene thus formed exhibits a layered structure with an average particle size in the range of 10–50 nm. The electrochemical studies demonstrate that the TTMXene nanocomposite exhibits a specific capacitance of 729 F g^–1 at a current density of 0.5 A g^–1. This enhanced performance is due to utilization of a high active surface area and excellent electronic conductivity of the in-situ formed TiO₂ in Ti₂C MXene. The prototype of a flexible symmetric TTMXene supercapacitor was fabricated and characterized. The TTMXene//TTMXene demonstrated an excellent energy density of 152.3 Wh kg^–1 at a power density of 0.215 kW kg^–1 and retained 88% specific capacitance after 10,000 cycles. These findings highlight that the TTMXene nanocomposites are exceptional candidates for future flexible supercapacitor devices with long-term and superior performance.

NaSICON-type materials, such as Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), are considered promising solid electrolytes due to their good total ionic conductivity of 1 × 10^–4 S cm^–1 at room temperature and their stability at high potentials (4.1 V vs Li/Li⁺). However, decreasing their densification temperature is crucial for their integration into all-solid-state batteries (ASSBs). The minimum required heat treatment temperature for densification of LATP is 900 °C, which is incompatible with its integration in the composite electrode of ASSBs due to reactivity with the positive electrode material (cathode). To lower this temperature, lithium salts are often proposed as sintering aids to promote liquid-phase sintering. However, the systematic formation of impurities, such as LiTiOPO₄ and Li₄P₂O₇, suggests that chemical reactivity plays a significant role in LATP densification. In this work, the chemical reactivity mechanism of lithium salts with LATP during densification and sintering was investigated. Various characterization techniques, including in situ and ex situ X-ray diffraction, TGA–DTA–MS, DSC, ex situ Raman and solid-state NMR spectroscopy (⁷Li, ²⁷Al, and ³¹P), were employed to elucidate the mechanism. The formation of intermediate decomposition products Li₃PO₄ and TiO₂ is identified for the first time via the reactivity of the lithium salt with LATP prior to the melting temperature of the salt. These intermediates subsequently react with LATP at a higher temperature, resulting in the formation of final impurities LiTiOPO₄ and Li₄P₂O₇. This unified mechanism provides important insights on the enhanced densification of LATP at lower temperatures with the use of Li salt sintering aids.

The Fe–N₄-based Fe single-atom catalyst exhibits high efficiency in oxygen reduction reaction (ORR) activity, while Co oxides demonstrate excellent oxygen evolution reaction (OER) activity. In this study, we report an easily synthesized carbon-based catalyst CoFe@CNT that incorporates both Fe single atoms and CoO nanoparticles. This catalyst is derived from a two-dimensional metalloporphyrin-based metal–organic framework (CoFeMOF) composed of an FeTCPP (5,10,15,20-tetrakis(p-carboxylphenyl)porphyrin iron) building unit coordinated with Co²⁺ and 4,4′-bipyridine. CoFe@CNT exhibits superior ORR (half-wave potential = 0.85 V) and OER (overpotential at 10 mA cm^–2 = 370 mV) performances and better stability compared to both ZnFe@CNT and Co@CNT (from the respective ZnFeMOF and CoMOF precursors) and commercial Pt/C catalysts. XPS analysis reveals that the presence of both Fe–N₄ single-atom and CoO nanoparticles in CoFe@CNT not only induces electron transfer from Co to Fe but also generates a higher combined content of pyridinic N and Fe–N₄ compared to both ZnFe@CNT and Co@CNT, which enhances the catalytic activity. A Zn–air battery using CoFe@CNT as the cathode catalyst achieves a high power density (115 mW cm^–2), outperforming the Pt/C catalyst. The design and synthesis of this 2D MOF-derived electrocatalyst offer promising prospects for developing high-density metal–air batteries.

A family of Co-based perovskites BaCo_1–xFe_xO₃ exhibits exceptional electrochemical activity as cathode materials for low-temperature solid-oxide fuel cells. Due to the size mismatch between Ba in the A-site and Co/Fe in the B-site, BaCo_1–xFe_xO₃ usually experiences phase transition from cubic symmetry at high temperatures to hexagonal structure at low temperatures and surface Ba-cation segregation. The phase transition would deteriorate bulk diffusivity and cause structural reliability issues, while the surface cation segregation could worsen surface-exchange property and long-term stability. Herein, A-site cation deficiency in combination with a B-site doping strategy is employed to tune the crystal structure and associated defects of Ba_1–xCo_0.6Fe_0.2Zr_0.1Y_0.1O_3−δ, achieving both excellent oxygen reduction reaction activity and stability. The materials are synthesized and systematically characterized. Compared to BaCo_0.6Fe_0.2Zr_0.1Y_0.1O_3−δ, the A-site deficient perovskite Ba_0.95Co_0.6Fe_0.2Zr_0.1Y_0.1O_3−δ obtains better electrochemical kinetics properties and stability as well as tolerance to CO₂. The fundamental mechanisms associated with these properties are discussed from the perspective of crystal structure, defects, charge-carrier transport route, average bonding energy, and surface cation segregation.

Plasmonic materials have emerged as very promising in investigating a wider range of catalytic reactions. In this work, we fabricated monometallic pure Ag substrates and bimetallic substrates by alloying Ag with Cu/Au and subsequently compared their catalytic efficiency using liquid-state in situ surface-enhanced Raman scattering (SERS). The liquid-state measurement annihilated any plasmon-induced thermal effect and thus provided insights into promoting plasmonic catalysis using this approach. Substrate fabrication was carried out using simple thermolysis of metal alkyl ammonium halide precursors (MToABr, where M = Ag, Au, and Cu) on glass coverslips and was thoroughly characterized. Two different laser excitation sources of 532 and 632.8 nm were used to inspect the C–C coupling reaction of the reactant 4-bromo-thiophenol (BTP) in water, and the rates of the reactions were monitored in kinetic mode at definite time intervals. Formation and time-dependent gradual increase of the peak at 1587 cm^–1 of the desired product 4,4′-biphenyldithiol (BPDT) and gradual decrease of the peak at 1560 cm^–1 of BTP indicated the reaction degree of the C–C coupling reaction. We also investigated the role of the hot carriers on our plasmonic substrates by selectively quenching the hot electrons or hot holes, using suitable scavenger solutions, and thereby proposed a suitable mechanism for the C–C coupling reaction. The bimetallic Ag–Cu substrate demonstrated almost a 5 times faster rate of catalysis for the C–C coupling reaction of 4-BTP than the bimetallic Ag–Au and pure Ag substrates when performed with 532 nm excitation.

Regulating electrode materials through structural design and compositional optimization can significantly enhance key performance metrics for lithium-ion batteries (LIBs), such as dynamic performance, cycling stability, and service life. Molybdenum trioxide (MoO₃) has emerged as a promising anode material for LIBs due to its high theoretical Li⁺ storage capacity (1117 mAh g^–1), low cost, and outstanding chemical stability. Nevertheless, the electrochemical performance of MoO₃ anodes is limited by poor intrinsic conductivity and significant volume expansion during cycling. To address the crucial issues, this study employs a simple carburization strategy to synthesize a three-dimensional porous carbon-supported, locally carbonized MoO₃ composite (MoO₃/Mo₂C/C) through strong coordination between Mo⁶⁺ metal cations and citric acid ligands. The elaborate structural design significantly enhances both conductivity and structural stability, leading to remarkable improvements in cycling performance. After 600 cycles, the composite anode maintains a discharge capacity of 1038.9 mAh g^–1 at 0.5 A g^–1 with a Coulombic efficiency of 99.97%, which is nearly 10 times that of the unmodified MoO₃ anode. In addition, a full battery is assembled with a LiFePO₄ cathode and the as-prepared MoO₃/Mo₂C/C anode to evaluate the practicality and reliability. As expected, the full battery delivers a high capacity of 122.1 mAh g^–1 at a current density of 0.1 A g^–1, demonstrating the promising strategy for the design of MoO₃ electrode materials.

Sulfide semiconductor materials are widely used in photocatalytic hydrogen production, and specifically, CdS-based photocatalysts have excellent photocatalytic performance. Here, the precursor of zinc cadmium diethyldithiocarbamate was synthesized using sodium diethyldithiocarbamate as a ligand, and then, ternary metal sulfide Zn–Cd–S nanorods were prepared by the solvothermal method using ethylenediamine as a solvent. The influence of the defect content on photocatalysis was investigated by adjusting the ratio of Zn and Cd. Surface defects can capture photogenerated holes, retain more photogenerated electrons, and serve as active centers for hydrogen evolution reactions. In addition, based on the first step, ZnS/Zn–Cd–S composite photocatalysts were synthesized by hydrothermal method. Due to the presence of Zn vacancies in ZnS, they can also be excited to generate photogenerated electrons under visible light conditions, forming a type-II heterojunction with Zn–Cd–S, promoting electron hole separation. The synergistic effect of heterojunction and surface defects greatly improves the photocatalytic performance of the catalyst, achieving high hydrogen resolution activity of 13.7 mmol·g^–1·h^–1.