ACS Applied Energy Materials最新文献

Developing high-capacity and fast-charging anode materials is critical for achieving high-performance Li-ion batteries (LIBs). Herein, polycrystalline quaternary transition metal silicon sulfides, Cu₂TSiS₄ (T = Fe, Mn), were synthesized using a solid-state method and investigated as anode materials in LIBs. Cu₂FeSiS₄ retains a reversible capacity of 670 mAh g^–1 at 200 mA g^–1 for 400 cycles, while Cu₂MnSiS₄ suffers from a fast capacity loss in the initial 50 cycles. More importantly, Cu₂FeSiS₄ can maintain a reversible capacity of 379 mAh g^–1 after 700 cycles at a high current density of 2 A g^–1, demonstrating high cyclic stability and fast-charging capacity. To further understand the structure degradation and phase transformation, we investigated the postcycling electrodes using multiple techniques, including the scanning electron microscope with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The results indicated that Cu₂FeSiS₄ undergoes reversible phase transitions with Li₂S as a major product component. To further assess the performance for practical applications, Cu₂FeSiS₄ was coupled with LiFePO₄ to make LiFePO₄||Cu₂FeSiS₄ full cells, which delivered superior electrochemical performance. These results demonstrate great promise for using quaternary transition metal silicon sulfides as anodes to achieve low-cost and sustainable LIBs.

In the past decade, the photovoltaic community has been motivated by the rapid development of perovskite solar cells (PSCs). Many approaches have been attempted to boost both the power conversion efficiency (PCE) and the stability of PSCs. Studies indicated that the processing additives could optimize the optoelectronic properties and film morphologies of metal halide perovskites, thereby boosting the device performance of PSCs. Herein, we report a boosted PCE and stability of the PSCs based on the MAPbI₃ (where MA⁺ is CH₃NH₃⁺) thin film, which is processed with urea additives. Compared to the pristine MAPbI₃ thin film, we find that the urea additives could suppress defects, enlarge crystallinity, boost charge transport, restrict nonradiative recombination, and enhance the hydrophobic properties of the resultant MAPbI₃ thin film. Thus, the PSCs based on the MAPbI₃ thin film processed with the urea additives exhibit a PCE of 22.02%, which is a 15% enhancement compared to those based on the pristine MAPbI₃ thin film. Moreover, the PSCs based on the MAPbI₃ thin film processed with the urea additives possess a remarkably boosted stability and suppressed photocurrent hysteresis compared to those based on the pristine MAPbI₃ thin film. Our studies demonstrate that metal halide perovskites processed with urea additives are a facile way to enhance the device performance of PSCs.

As is well-known, the lower open-circuit voltage (V_OC) and fill factor (FF) are two major reasons for the lower efficiency of Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells. K-doping has become an effective means of improving the efficiency. In this work, the effect of K-doping on power conversion efficiency (PCE) was studied in a K-doping concentration (K/Cu) of 0 to 15 mol % at a selenization temperature ranging from 490 to 530 °C. As a result of our study, it was found that the optimal K-doping concentration for obtaining the highest PCE decreases with increasing selenization temperature. Through optimizing the K-doping concentration and selenization temperature, the highest PCE of 10.15% is obtained at K/Cu = 10 mol % and 510 °C. It is proved that the increased PCE induced by K-doping at a fixed selenization comes mainly from the decreased reverse saturated current density (J₀), then from the photogenerated current density (J_L), series resistance (R_S), and shunt resistance (R_Sh).

Osmotic energy, often called blue energy, is a promising renewable resource. Nanofluidic reverse electrodialysis, which utilizes nanoflows to generate power, has gained intensive attention as a promising technology for harvesting osmotic energy. However, efficiency challenges have hindered its widespread application. In this study, we proposed a strategy to enhance the osmotic energy harvesting efficiency by applying a pressure gradient, taking easily accessible anodic aluminum oxide membranes as the representative model. Our results demonstrate that the pressure difference across the membrane gives rise to a substantial enhancement in osmotic current for a wide range of pore sizes and salt ions. Specifically, a 1 bar pressure difference results in a 130% increase in osmotic current under a 1000-fold concentration gradient of potassium chloride solution. The pressure-enhanced osmotic power generation is attributed to the additional ion flux driven by pressure gradient and thus a higher electrical conductivity across the membrane. These findings highlight the potential of pressure-driven enhancements to improve the efficiency of blue energy technologies.

Oxygen reduction reaction (ORR) is an indispensable electrochemical reaction in fuel cells. However, the performance of fuel cells has been affected by the slack kinetics of the ORR. Hence, the development of efficient and affordable electrocatalysts for the reduction of O₂ is necessary for the large-scale commercialization of fuel cells. Here, we present a Ni₂ dual-atom anchored on a N-doped carbon nanotube (Ni₂_N₃_CNT and Ni₂_N₄_CNT) and a Ni single-atom anchored on N-doped carbon nanotube (Ni₁_N₃_CNT and Ni₁_N₄_CNT) catalysts with two possible active sites, namely, Ni-site and N-site, as efficient catalysts toward the ORR. We have analyzed the energetically favorable active site for O₂ reduction on the surface of the Ni₁_N₃_CNT, Ni₁_N₄_CNT, Ni₂_N₃_CNT, and Ni₂_N₄_CNT catalysts by employing the density functional theory method with van der Waals (vdW) dispersion corrections (in short the DFT-D3) method. Among all possible configurations, Ni₂_N₃_CNT is a more favorable configuration with the Ni catalytic active site toward the ORR. Then, we have studied the structural, electronic, and catalytic activity of Ni₂_N₃_CNT by using the same DFT-D3 method. The analysis of the ORR intermediate species reveals that the associative reaction pathway is a more favorable path for reducing the O₂ into H₂O at the Ni catalytic site of Ni₂_N₃_CNT than the dissociative reaction pathway. In the free energy profile, all of the ORR reaction intermediate steps are downhill, indicating the good catalytic activity of Ni₂_N₃_CNT toward the ORR. Moreover, we have also studied the structural and electronic properties of all of the reaction intermediate steps by employing the same DFT-D3 method. These findings point out that the Ni₂ dual-atom catalysts provide an efficient electrocatalytic activity toward the ORR, and it holds great promise as a replacement for Pt-based catalysts in future proton-exchange membrane fuel cells. This work highlights the potential and importance of the subject material as a durable electrocatalyst for the ORR, offering insights into Ni₂ dual-atom electrochemistry and the design of advanced catalysts, which may be a promising candidate to substitute for Pt electrodes, and it is an excellent material for fuel-cell components.

Decoupled water electrolysis, which utilizes redox mediators to separate the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in space and time, is considered a potential method for producing high-purity green hydrogen. However, there are some key challenges in decoupled water electrolysis using solid-state redox mediators, such as redox potentials, voltage distribution, capacity limitations, and material stability. Here, F-doped Na_0.7MnO_2.05 (NMOF) with an appropriate redox potential, high capacity, and stability was synthesized by a simple sol–gel method. The redox peak pair of NMOF was located at −0.064 V/–0.314 V (vs Hg/HgO), which is located between the onset potentials of the HER and OER. By F-doping, F–Mn bonds significantly inhibited the dissolution of Mn²⁺ in the electrolyte, thereby reducing the Jahn–Teller effect and improving the cycling stability of Na-ion insertion and removal in Na_0.7MnO_2.05. NMOF prepared by adding 5 mol/% NaF at 850 °C (named NMOF2) exhibited excellent electrochemical performance, with a discharge capacity of 114.3 mAh/g at a current density of 0.5 A/g. Using NMOF2 for decoupled water electrolysis, voltage balance distribution was achieved, and hydrogen and oxygen production was achieved at such low voltages (0.85 V for the HER process and 0.89 V for the OER process) at a current density of 5 mA/cm². These suggest that NMOF2 could be a promising material for decoupled water electrolysis.

Carbon nanofibers (CNFs) have important application potential in the field of supercapacitors; however, the relatively low specific surface area often leads to a low capacitance. Herein, N-doped carbon nanofibers/carbon nanorods (CNFs/CNRs-N) composite with an N-doping level up to 8.9 atom % is designed, which shows excellent supercapacitor energy storage performance. CNFs/CNRs-N has a three-dimensional porous structure, a large specific surface area, and a huge number of active sites. Based on the synergy of various unique properties of CNFs/CNRs-N, when used as a supercapacitor electrode material, it shows a specific capacitance value of up to 595 F g^–1.

Hybrid lead halide perovskite solar cells (PSCs) stand out in terms of their high efficiency, yet the limited stability and process scalability pose challenges to their commercialization. Fully printable carbon-based perovskite solar cells (C-PSCs), consisting of a triple stack of mesoporous titania, zirconia, and carbon layers impregnated with the perovskite material, have been introduced as an attractive architecture; however, they generally exhibit lower efficiency. This study proposes a viable and scalable approach to increase the efficiency of C-PSCs by incorporation of an intermediate layer of mesoporous, nanostructured NiCo₂O₄ between the zirconia and carbon layers. The devices show an average increase in power conversion efficiency from 7.9 to 11%, with a champion device efficiency of 12.4%, associated with an enhanced average open-circuit voltage (V_OC) from 0.869 to 0.962 V. Electrochemical impedance spectroscopy reveals that the high-frequency recombination resistance (R_HF) decreases exponentially with V_OC with the same slope as for the reference triple-stack system, indicating that the mechanism is unchanged; however, a substantial increase in R_HF is observed. These results indicate that the hole extraction efficiency improves upon incorporation of the NiCo₂O₄ film thus decreasing surface recombination at the nonselective carbon contact. On the other hand, we postulate a possible contribution of the high capacitance of the interlayer, which may result in a shift of the Fermi energy of the carbon electrode and play a role in the hysteresis in the current - voltage curve.

The development of high-performance all-solid-state ion batteries necessitates the design of solid-state electrolytes (SSEs) with high ionic conductivity and excellent electrochemical stability. Antiperovskite (AP) X₃BA, as the electronically inverted derivative of perovskite ABX₃, has garnered significant attention in the field of energy storage batteries due to its superior ionic conductivity. However, the relationship between their structure and ion diffusion behavior warrants further investigation. In this work, we constructed a machine learning (ML) framework for predicting and analyzing the ionic conductivity of the AP SSE, which encompasses data collection, feature selection, and training of various ML models. The optimal ML model demonstrated an exceptional classification performance, achieving an accuracy rate as high as 94%. Furthermore, we employed the ion substitution method to expand the sample size from 168 to 150,000 orders of magnitude. Based on this expanded data set, we examined and analyzed the mechanisms underlying high ionic conductivity from a big data perspective. The findings reveal a strong correlation between the ionic conductivity and atomic-scale characteristics at the A-site. The electronegativity, density, and ionic radius at the A-site are identified as the three most critical features influencing ionic conductivity. The interpretable ML model constructed in this study enables high-precision prediction of the ionic conductivity of AP materials, provides insightful design principles, and significantly accelerates the development and application of AP SSEs.

Engineering the molybdenum disulfide (MoS₂) and reduced graphene oxide hybrid via layer-by-layer stacking is an efficient way to enhance the thermoelectric performance by decoupling the Seebeck coefficient and electrical transport. The fabricated MG achieved maximum of −25.2 μV K^–1 at 325 K, 23.5 S m^–1 at 351 K, and 15.5 nW m^–1 K^–2 at 325 K for the Seebeck coefficient, electrical conductivity, and power factor, respectively. The π–π interactions at the interface of MoS₂-rGO, where the low charge carriers (cold electrons) are scattered without affecting the mobility, simultaneously enhanced the thermoelectric performance through the decoupled Seebeck coefficient and electrical conductivity.