ACS Applied Energy Materials最新文献

By chemically tuning the surface of precipitated silica, we propose an approach to vary the hydrophilicity and elucidate its impact on the state of dispersion of silica aggregates in hydrophobic materials. Precipitated silica underwent reversible chemical modification, which transformed its surface from a hydrophilic surface to a hydrophobic surface in order to promote interactions with hydrophobic environments, e.g., suspension of silica in hydrophobic solvents and dispersion in nanocomposites. Hence, tunable hydrophobic molecules, i.e., 3-mercaptopropyltrimethoxysilane (MPTMS), were grafted onto the surface of silica. In the first step, the properties of the surface of silica were adapted to enhance the dispersion of particles in a hydrophobic medium (e.g., processing hydrophobic polymers filled with silica). Afterward, the obtained modified silica underwent chemical tuning to recover part of its initial hydrophilicity, which is desired for some applications like battery separators. Thereby, the grafted molecules onto the surface of the silica were oxidized to decrease the hydrophobicity of the grafted functions. For each surface treatment of silica particles, solid-state NMR analyses were used to confirm qualitatively the presence of the grafted molecules onto the surface of silica, and TGA analysis and conductance measurements were used to quantify the grafted molecules. Water sorption isotherms were also used to characterize the hydrophilic change of silica. Finally, the obtained silicas were used in formulations of UHMWPE (ultrahigh molecular weight polyethylene)–silica battery separators that were characterized by scanning electron microscopy (SEM), small-angle neutron scattering (SANS), porosity measurements, and electrical resistance measurements. The silica grafted and then oxidized presented the best dispersion in the UHMWPE while presenting the high hydrophilicity needed for the low resistivity of the membrane.

Hydrogen is crucial for achieving carbon neutrality and sustainable energy. To commercialize water electrolysis technology, the development of high-performance OER catalysts is essential. This study utilizes seawater as an electrolyte to enhance economic viability and employs Ni-based materials instead of precious metals like RuO₂. Ni-based Hofmann-type coordination polymers were synthesized via plasma engineering and transformed into 2D Ni nanoplates through thermal treatment. These nanoplates demonstrated exceptional OER performance in both alkaline and alkaline seawater electrolytes, achieving lower overpotentials compared to that of RuO₂. In situ Raman spectroscopy revealed that seawater’s diverse cations and anions increased the disorder of the active phase (NiOOH) through intercalation, suppressing Ni oxidation and active oxygen formation, which reduced OER activity. In an anion exchange membrane water electrolyzer (AEMWE) under alkaline seawater, Ni nanoplates exhibited much lower cell voltages of 267 and 393 mV at current densities of 500 and 1000 mA cm^–2, respectively, compared to RuO₂. Notably, the cell voltage showed negligible changes over 90 h during a durability test at 100 mA cm^–2. This work highlights Ni-based Hofmann-type coordination polymers and their derivatives as efficient OER catalysts for hydrogen generation.

Engineered electrolytes are critical for high-performance lithium–sulfur batteries (LSBs). Present electrolyte selection for simultaneously forming a stable bilateral solid–electrolyte interface (SEI) on both electrodes is largely heuristic. Although the dielectric constant, viscosity, dipole moment, donor number, and orbital energy levels have all been used for electrolyte screening, their effectiveness has not been systematically studied. Here, the effectiveness of these parameters was investigated using a key metric of battery performance. Based on 51 mixed electrolytes investigated in this study, the enhanced stability of LSBs is attributed to the mixed electrolytes’ high dielectric constant (ε > 35), which ensures the separation of the LiTFSI salt ions and potentially reduces dendrite growth. However, 3 other high dielectric (ε > 35) mixed electrolytes based on diglyme exhibited a % drop of > ± 1.4%, which is ∼2 times larger than the % drop exhibited by batteries with high dielectric (ε > 35) compositions devoid of diglyme. Classical molecular dynamics indicated the presence of large diglyme molecules in the solvation shell, causing a ∼30% reduction in diffusivity and adversely affecting battery performance. This study indicates that a high dielectric constant (ε > 35) along with the absence of large molecules in the solvation shell are good criteria for LSB mixed electrolyte selection.

Increasing the crystallinity of carbon nitride can accelerate the photogenerated carrier migration rate and reduce the structural defects, which is an effective strategy to improve the photocatalytic performance of carbon nitride. In this work, carbon nitride microtubes were post-treated in KCl-LiCl molten salts to create crystalline heptazinyl carbon nitride microtubes. The results show that photocatalytic hydrogen production rate of the as-prepared crystalline heptazine-based carbon nitride microtubes can reach 3440.21 μmol·g^–1·h^–1, which is approximately 28.8, 2.1, and 22.2 times higher than that of bulk carbon nitride, sulfur doped g-C₃N₄ microtubes, and microtubes with triazine-based structure prepared by a one-step molten salt method, respectively. The carbon nitride microtubes prepared by this method have a heptazine-based structure, possessing not only high crystallinity but also significantly increased specific surface area. This study offers a reliable guide for designing an innovative approach to prepare semiconductor photocatalysts in the molten salt system.

This study reports the synthesis of ZnO nanosheets, nanorods, and nanotubes through electrodeposition, followed by the deposition of MoS₂ layers using RF magnetron sputtering to create ZnO/MoS₂ heterostructures. The morphological and structural properties of these materials were characterized using various techniques, including X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–visible spectroscopy. The photoelectrochemical (PEC) performance of synthesized ZnO and ZnO/MoS₂ heterostructures for water splitting was evaluated. Results indicate that the morphology of ZnO significantly influences the PEC activity of the ZnO/MoS₂ heterostructures. The ZnO/MoS₂ heterostructure with ZnO nanotubes exhibited the highest PEC performance, achieving a photocurrent density of ∼1.28 mA/cm² at 1.65 V versus reversible hydrogen electrode, which is 2.5 times greater than that of the pristine ZnO nanotube photoanode. This study suggests that ZnO/MoS₂ heterostructures can be promising photoanodes for efficient hydrogen production through PEC water oxidation.

This study investigates the defect properties and doping limitations of group V elements in CdSe_xTe_1–x. Group V acceptor dopants are able to increase hole concentrations and thereby enhance solar cell performance. However, their doping efficiency is limited by the formation of compensating donor defects with concentrations that depend on alloy composition, processing temperatures, and Cd segregation into grain boundaries. We use density functional theory (DFT) and lattice Monte Carlo (LMC) to identify the lowest-energy Se/Te alloy configurations and to understand the impact of temperature and local alloy configuration on As/P defect formation. Continuum simulations were then employed based on the results of the DFT and LMC calculations to explore As/P dopability in CdSeTe under various growth temperatures, initial chemical potentials, and alloy compositions. Moreover, the segregation of Cd at grain boundaries was investigated to understand its impact on compensating defects. The results of our LMC simulations suggest that P should be a more effective p-type dopant than As in CdSeTe, while both dopants become less effective as Se content increases. Additionally, the continuum simulations highlight that both As and P doping can enhance p-type conductivity, and both of them can reach hole density on the order of 10¹⁶ cm^–3 for 873 K initial growth temperature and 10¹⁷ cm^–3 for 1173 K initial growth temperature. We find that managing chemical potentials and the formation of compensating defects is crucial for optimizing carrier density and dopant activation efficiency and ensuring they remain stable.

Ag₂Se thin film devices have attracted significant interest in energy harvesting technologies for powering microscale systems. In this work, an in situ selenide diffusion strategy is employed to prepare Ag₂Se thin films, optimizing the carrier transport by tuning in situ synthesis temperature. The optimized carrier mobility of ∼871.43 cm^–2 V^–1 s^–1 is achieved, leading to a high room-temperature electric conductivity of ∼1235 S cm^–1. Correspondingly, a decent Seebeck coefficient (|S| > 120 μV K^–1) is obtained due to the optimal carrier concentration of approximately 1 × 10¹⁹ cm^–3. Consequently, the Ag₂Se film synthesized at 423 K exhibits a high power factor of ∼20.54 μW cm^–1 K^–2 at room temperature. A thermoelectric generator with 5 single legs is assembled by Ag₂Se thin films. This device is capable of generating an output voltage of approximately 8.58 mV and a corresponding power of approximately 3.76 nW when subjected to a temperature difference of 40 K. The study presents an effective method for enhancing the thermoelectric performance of Ag₂Se thin films.

Electrolysis of impure water (such as seawater) has recently garnered research interest as it may enable hydrogen production at reduced costs. However, the tendency of impurity ions and other species to degrade electrocatalysts and membranes within an electrolyzer is a serious challenge. Here, we investigate the effects of copper impurities of varying concentrations on the hydrogen evolution reaction (HER) using platinum electrocatalysts. A decrease of current density is observed with an increasing copper concentration. By comparing the effect of ionic impurities on current density at different concentrations, we gain insight into how impurities can interfere with the HER at different potentials. Surface characterization of the electrodes reveals differences in the morphology and extent of copper deposition on HER-active platinum vs inactive gold electrodes. This enables an improved understanding of how copper nucleates and grows on the two types of electrodes under different electrochemical conditions while also confirming deposition in low-concentration cases, as present in seawater. The results indicate that copper electrodeposition competes with the HER, and the nature of copper electrodeposition varies depending on the electrocatalytic activity of the electrode. This study provides insight toward catalyst design that can withstand the effects of impurity-induced degradation over extended use.

Fiber-typed supercapacitors are promising energy storage devices for wearable electronics, and the microstructure of graphene fiber electrodes for flexible supercapacitors plays a significant role in the ion diffusion efficiency and energy density improvement. In this paper, we report a coaxial microfluidic spinning technology, ammonium bicarbonate solution as the core flow, and graphene oxides and MXene quantum dots (MQDs) composite spinning dispersion as the sheath flow to fabricate the hierarchical porous MQDs/graphene composite fibers (MQDs@PGF). 0D MQDs as electrochemically active materials were intercalated into graphene nanosheets; the ammonium bicarbonate solution acts as a foaming agent to realize a hierarchical porous structure of micro-meso-macroporous and a large specific surface area (68.8 m² g^–1), which greatly shorten the ion diffusion channels and provide more electrochemically active sites. The assembled fiber-typed supercapacitors (MQDs@PGF FSCs) exhibit a high specific areal capacitance of 1288 mF cm^–2 and maintain a high capacitance retention of 95% after 9000 cycles. The MQDs@PGF FSCs achieve an excellent energy density of 147.5 μWh cm^–2 under a wide operating voltage window of 0–2.5 V and successfully power small electronic devices. This method provides a strategy for the controllable design of high-performance fiber electrode materials and promotes energy storage applications in wearable portable devices.

Electrolysis of impure water (such as seawater) has recently garnered research interest as it may enable hydrogen production at reduced costs. However, the tendency of impurity ions and other species to degrade electrocatalysts and membranes within an electrolyzer is a serious challenge. Here, we investigate the effects of copper impurities of varying concentrations on the hydrogen evolution reaction (HER) using platinum electrocatalysts. A decrease of current density is observed with an increasing copper concentration. By comparing the effect of ionic impurities on current density at different concentrations, we gain insight into how impurities can interfere with the HER at different potentials. Surface characterization of the electrodes reveals differences in the morphology and extent of copper deposition on HER-active platinum vs inactive gold electrodes. This enables an improved understanding of how copper nucleates and grows on the two types of electrodes under different electrochemical conditions while also confirming deposition in low-concentration cases, as present in seawater. The results indicate that copper electrodeposition competes with the HER, and the nature of copper electrodeposition varies depending on the electrocatalytic activity of the electrode. This study provides insight toward catalyst design that can withstand the effects of impurity-induced degradation over extended use.