Direct synthesis of layer-tunable and transfer-free graphene on technologically important substrates is highly valued for various electronics and device applications. Here, we report a novel synthesis approach combining ion implantation for a precise graphene layer control and dual-metal smart Janus substrate for a diffusion-limiting graphene formation, to directly synthesize layer-tunable graphene on arbitrary substrates without the post-synthesis layer transfer process. C ion implantation was performed on Cu-Ni film deposited on a variety of device-relevant substrates. Upon thermal annealing to promote Cu-Ni alloying, the pre-implanted C-atoms in the Ni layer are pushed towards the Ni/substrate interface by the top Cu layer due to the poor C-solubility in Cu. As a result, the expelled C-atoms precipitate into graphene structure at the interface facilitated by the Cu-like alloy catalysis. After removing the alloyed Cu-like surface layer, the layer-tunable graphene on the desired substrate is directly realized. ReaxFF was performed to elucidate the graphene formation mechanisms in this novel synthesis approach. Three ordinary devices using as-synthesized graphene were fabricated on Si, SiO2, and glass substrates to demonstrate the graphene quality of our layer-tunable and transfer-free synthesis approach and the excellent performance characteristics of these low-cost manufacturing devices: field-effect transistors, heating devices, and near-infrared photodetectors.
Aqueous rechargeable zinc-ion batteries (ZIBs) have garnered considerable attention due to their safety, cost-effectiveness, and eco-friendliness. There is a growing interest in finding suitable cathode materials for ZIBs. Layered vanadium oxide has emerged as a promising option due to its ability to store zinc ions with high capacity. However, the advancement of high-performance ZIBs encounters obstacles such as sluggish diffusion of zinc ions resulting from the high energy barrier between V2O5 layers, degradation of electrode structure over time and consequently lower capacity than the theoretical value. In this study, we investigated the pre-doping of different cations (including , , and ) into V2O5 to enhance the overall charge storage performance. Our findings indicate that the presence of V4+ enhances the charge storage performance, while the introduction of into V2O5 (NH4-V2O5) not only increases the interlayer distance (d(001) = 15.99 Å), but also significantly increases the V4+/V5+ redox couple (atomic concentration ratio increased from 0.14 to 1.08), resulting in the highest electrochemical performance. The NH4-V2O5 cathode exhibited a high specific capacity (310.8 mAh g-1 at 100 mA g-1), improved cycling stability, and a significantly reduced charge transfer resistance compared to pristine V2O5.
Thick and highly conductive PEDOT:PSS films with ideal morphologies, are desirable as electrodes for supercapacitors. However, building uniform micro-morphology without templates or composite strategies is a formidable challenge, primarily caused by the inherent softness of dominant PSS. Herein, we successfully realized morphology control, transitioning from a layer-by-layer architecture to a porous structure in thick PEDOT:PSS films by employing solvothermal method with ethylene glycol (EG) as the solvent. The combined effect of high pressure and temperature effectively drove EG to construct the microstructure of thick PEDOT:PSS films by detaching insulating PSS chains and enhancing PEDOT crystallinity, and simultaneously facilitated the formation of a porous network through EG molecular tailoring. The achieved porous thick PEDOT:PSS films delivered a high conductivity of 1644 S cm-1 and a champion specific capacitance of 270 F cm-3, significantly surpassing previously reports. The flexible all-solid-state supercapacitor assembled based on the films displayed an excellent specific capacitance of 97.8 F cm-3 and an energy density of 8.7 mWh cm-3, representing the highest values for pure PEDOT:PSS-based supercapacitors. This research provides an effective novel method for conducting polymer morphology control and promotes the applications of PEDOT:PSS in the field of energy storage.
In this work, we reported a series of monolithic 3D-printed Ni-Mo alloy electrodes for highly efficient water splitting at high current density (1500 mA cm-2) with excellent stability, which provides a solution to scale up Ni-Mo catalysts for HER to industry use. All possible Ni-Mo metal/alloy phases were achieved by tuning the atomic composition and heat treatment procedure, and they were investigated through both experiment and simulation, and the optimal NiMo phase shows the best performance. Density functional theory (DFT) calculations elucidate that the NiMo phase has the lowest H2O dissociation energy, which further explains the exceptional performance of NiMo. In addition, the microporosity was modulated via controlled thermal treatment, indicating that the 1100 C sintered sample has the best catalytic performance，which is attributed to the high electrochemical surface area (ECSA). Finally, the 4 different macrostructures were achieved by 3D printing, and they further improved the catalytic performance. The gyroid structure exhibits the best catalytic performance of driving 500 mA cm-2 at a low overpotential of 228 mV and 1500 mA cm-2 at 325 mV as it maximizes the efficient bubble removal from the electrode surface, which offers the great potential for high current density water splitting.
Electrocatalytic reduction of CO2 into high energy-density fuels and value-added chemicals under mild conditions can promote the sustainable cycle of carbon and decrease current energy and environmental problems. Constructing electrocatalyst with high activity, selectivity, stability and low cost is really matter to realize industrial application of electrocatalytic CO2 reduction (ECR). Metal-nitrogen-carbon (M-N-C) electrocatalysts, especially Ni-N-C, display excellent performance, such as nearly 100% CO selectivity, high current density, outstanding tolerance, etc., which is considered to possess broad application prospects. Based on the current research status, starting from the mechanism of ECR and the existence form of Ni active species, the latest research progress of Ni-N-C electrocatalysts in CO2 electroreduction is systematically summarized. An overview is emphatically interpreted on the regulatory strategies for activity optimization over Ni-N-C, including N coordination modulation, vacancy defects construction, morphology design, surface modification, heteroatom activation, bimetallic cooperation. Finally, some urgent problems and future prospects on designing Ni-N-C catalyst for ECR are discussed. This review aims to provide the guidance for the design and development of Ni-N-C catalyst with practical application.
Aqueous zinc-ion batteries (AZIBs) are regarded as the promising candidates for large-scale energy storage systems owing to low cost and high safety; however, their applications are restricted by their poor low-temperature performance. Herein, a low-temperature electrolyte for low-temperature AZIBs is designed by introducing low-polarity diglyme (DGM) into an aqueous solution of Zn(ClO4)2. The DGM disrupts the hydrogen-bonding network of water and lowers the freezing point of the electrolyte to -105 °C. The designed electrolyte achieves ionic conductivity up to 16.18 mS cm-1 at -45 °C. The DGM and ClO4- reconfigure the solvated structure of Zn2+, which is more favorable for the desolvation of Zn2+ at low temperatures. In addition, the DGM effectively suppresses the dendrites, hydrogen evolution reaction, and by-products of the zinc anode, improving the cycle stability of the battery. At -20 °C, a Zn||Zn symmetrical cell is cycled for 4,500 h at 1 mA cm-2 and 1 mA h cm-2, and a Zn|| polyaniline (PANI) battery achieves an ultra-long cycle life of 10,000 times. This study sheds light on the future design of electrolytes with high ionic conductivity and easy desolvation at low temperatures for rechargeable batteries.
This study explores enhancing salinity gradient power using 2D materials due to their surface-governed charge. However, achieving high-performing membranes with superior ion selectivity and low ionic resistances remains challenging. To address this issue, Al(OH)4- anions were incorporated into graphene oxide membranes to increase their spontaneous negative surface charge. The anions were successfully formed and encapsulated through a reaction with the alumina support under alkaline conditions during the membrane formation. The membranes’ physicochemical properties were analyzed by means of selected characterization techniques. The incorporation of Al(OH)4- anions significantly improved permselectivity and ionic resistance, reaching approximately 95% and 2 Ω cm2, respectively. A modeling of the system was carried out to further understand the anchoring of these ions within the membrane matrix and their role in boosting the charge of the membrane and, therefore, their electrochemical properties. The study delved into the utilization of GO membranes as monovalent-selective membranes, an approach to boost reverse electrodialysis power densities. The membranes demonstrated impressive selectivity, overcoming 70 folds for divalent cations over K+.
The development of high-performance organic solar cells (OSCs) with high operational stability is essential to accelerate their commercialization. Unfortunately, there is currently a lack of detailed understanding of the origin of instabilities in state-of-the-art OSCs based on bulk heterojunction (BHJ) featuring non-fullerene acceptors (NFAs). Herein, we developed NFA-based OSCs using different charge extraction interlayer materials and studied their storage, thermal, and operational stabilities. Despite the high power conversion efficiency (PCE) of the OSCs (17.54%), we found that cells featuring self-assembled monolayers (SAMs) as hole-extraction interlayers exhibited poor stability. The time required for these OSCs to reach 80% of their initial performance (T80) was only 6 h under continuous thermal stress at 85 °C in a nitrogen atmosphere and 1 h under maximum power point tracking (MPPT) in a vacuum. Inserting MoOx between ITO and SAM enhanced the T80 to 50 h and ~15 h after the thermal and operational stability tests, respectively, while maintaining a PCE of 16.9%. Replacing the organic PDINN electron transport layer with ZnO NPs further enhances the cells’ thermal and operational stability, boosting the T80 to 1000 and 170 h, respectively. Our work reveals the synergistic role of charge interlayers and device architecture in developing efficient and stable OSCs.
Radiative cooling materials continue to underperform compared to their theoretical potential due to parasitic heating from contact with ambient air. Solutions to this problem are expensive or complex to fabricate. Here, a potentially inexpensive, simply fabricated material that improves cooling performance by reducing parasitic heating was created using naturally abundant salts. NaCl and KCl are not typically considered for radiative cooling because of their high hygroscopicity and low mechanical strength; however, these compounds are highly infrared-transparent and can be fabricated into aerogel-like structures to provide thermally insulating properties. Salt aerogels, described herein, scattered (reflected) visible light, transmitted infrared radiation, and provided thermal insulation. They were packaged into mechanical supporting panels to avoid physical disruption and the nanostructure was stabilized to moisture by adding anti-caking agent. The panels were able to keep an underlying surface below ambient temperature for a full 24-hour cycle and reduced parasitic heating rate by more than half (compared to an uncovered surface). The panels were able to cool a variety of underlying surfaces, even highly absorbing surfaces that are normally well above ambient temperature during the day. This work demonstrates an affordable, easily produced, electricity-free cooling technology with potential to be manufactured for large-scale practical applications.