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We develop an ultrafast, high-detectivity, self-powered broadband PD based on SnO2 nano litchi shell structure/n-Si heterojunction. The excellent performance attributed to the SnO2 nano litchi shell structure, and meaningful interface barrier.

Potassium-selenium (K-Se) batteries have attracted significant attention as one of the most promising alternatives of lithium-ion storage systems owing to high energy density and low cost. In the design of Se-based cathode materials, however, the low utilization rate of active Se and the rapid dissolution of polyselenides seriously weaken the capacity and cycle stability. Therefore, how to make full use of Se species without loss during the charge and discharge process is the key to design high-performance Se-based cathode. In this paper, a 3D “water cube”-like Se/C hybrid (denoted as Se−O−PCS) is constructed with the assistance of Na2CO3 templates. Thanks to the abundant carbonate groups (CO32−) originated from the Na2CO3 templates, the molten Se species are firmly anchored into the pore of carbon skeleton by strong C−O−Se bonding. Thus, this unique Se−O−PCS model not only improves the utilization of active Se species, but also can reduce the contact with the electrolyte to inhibit the shuttle effect of polyselenides. Moreover, flexible carbon skeleton gives Se-O-PCS hybrid a good electrical conductivity and excellent structural robustness. Consequently, the resultant Se−O−PCS hybrid is endowed with an obviously enhanced K-ions storage property.

Enhancing pseudocapacitance of Ti3C2Tx MXene-based electrode materials induced by sufficient surface terminating groups (such as Ti–O bonding) becomes one promising way for fabricating high energy-density supercapacitors. However, most of terminating group activity cannot be excited well in the multilayer Ti3C2Tx due to the layer stacking feature, which limits its further performance improvement. In this paper, a CQDs@Ti3C2Tx hybrid material is synthesized by modifying few-layer Ti3C2Tx MXene matrix with highly dispersed carbon quantum dots (CQDs). In this unique hybrid model, the Ti3C2Tx MXene matrix with high conductivity and high specific surface area is just like the “paddy field”, which not only promotes the charge rapid transfer, but also provides the high double layer capacitance by ion adsorption. More importantly, the CQDs act as “rice seedlings” firmly anchored to the Ti3C2Tx matrix, and greatly stimulate the activity of the termination groups of Ti3C2Tx. As expected, this hybrid achieves a harmonious coexistence of high conductivity and high pseudocapacitance. As a result, the CQDs@Ti3C2Tx electrode delivers high reversible capacitances of 441.3 F g−1 at 1 A g−1 and 310.1 F g−1 at 20 A g−1, and a relatively stable cyclability with almost 100% capacitance retention after 10 000 cycles at 10 A g−1.

To confirm the rules and transformation conditions of shale gas adsorption and establish a model for evaluating the adsorption capacity of shale gas quantitatively, it is necessary to reveal the shale gas adsorption mechanism. The adsorption mechanism of CH4 and CO2 in Kaolinite slit nanopores has been studied under the simulated conditions of 90 °C and 30 or 50 MPa by the grand canonical Monte Carlo (GCMC) method. The results indicate that CH4 is controlled only by the Van der Waals forces on the mineral surface because CH4 is nonpolar, while CO2 is controlled by both Van der Waals forces and Coulomb forces due to a certain electric quadrupole moment, which makes the adsorption capacity of CO2 on kaolinite greater than that of CH4. Due to the overlapping adsorption potential on the kaolinite surface of micropores (1 nm), the peak of the density profile is higher in the micropores than the peak in the mesopores (4 nm), resulting in the filling effect in the micropores. On the surface of the silicon-oxygen octahedron, the adsorption site for CH4 and CO2 is in the center of the silicone hexagon-ring, and CO2 with a quadrupole moment shifts near the polar oxygen atoms. In contrast, the adsorption sites of CH4 are relatively dispersed on the surface of the aluminum-oxygen octahedron with a hydroxyl group, while the adsorption sites of CO2 are concentrated in the location of the aggregated oxygen atoms. When CH4 and CO2 coexist, CO2 tends to be adsorbed prior to CH4. With the proportion of CO2 increasing, the competitive adsorption effect is gradually aggravated, which suggests the rationality of injecting CO2 to improve the recovery efficiency of shale gas. These findings can provide theoretical support for shale gas exploration and development.

Exploring novel NH

Aluminum-ion batteries (AIBs) are a type of promising energy storage device due to their high capacity, high charge transfer efficiency, low cost, and high safety. However, the most investigated graphitic and metal dichalcogenide cathodes normally possess only a moderate capacity and a relatively low cycling stability, respectively, which limit the further development of high-performance AIBs. Here, based on the results of first principles calculations, we developed a polyaniline/graphene oxide composite that exhibited outstanding performances as a cathode material in AIBs (delivering 180 mA h g− after 4000 cycles), considering both the discharge capacity and the cycling performance. Ex-situ characterizations verified that the charge storage mechanism of polyaniline depended on the moderate interactions between −NH in the polyaniline chain and the electrolyte anions, such as AlCl4−. These findings lay the foundation of the development of high-performance AIBs based on conducting polymers.

The development of lead-free ceramics with high recoverable energy density (Wrec) and high energy storage efficiency (η) is of great significance to the current energy situation. In this work, a new scheme was proposed to improve the Wrec and η of potassium sodium niobate ((K, Na)NbO3, abbreviated as KNN) lead-free ceramics. Doping Bi elements in KNN ceramics to form a second phase (K2BiNb5O15) can reduce the grain size and form Schottky-like contact. Meanwhile, the hybridization between the Bi 6p and O 2p orbitals can enhance the maximum polarization (Pmax). So the K1-3xBixNa0.5NbO3-1 mol%CuO ceramics was proposed to improve the Wrec of lead-free ceramics. A large Wrec (2.89 J/cm3) and dielectric breakdown strength (DBS) (300 kV/cm with a thickness of 0.2 mm) were achieved for K0.14Bi0.12Na0.5NbO3-1 mol%CuO ceramics. The high Wrec was supposed to benefit from low remnant polarization (Pr), high Ps and DBS of ceramics. In addition, a large η (80%) was simultaneously achieved for K1-3xBixNa0.5NbO3-1 mol%CuO ceramics, which is superior to mostly reported lead-free bulk ceramics. The results show that K1-3xBixNa0.5NbO3-1 mol%CuO ceramics have a good application prospect in the field of energy storage, and provide a new scheme for the preparation of lead-free ceramics with high energy storage density and high conversion efficiency.

It is of great significance to develop novel superhydrophilic/underwater superoleophobic materials using a facile and simple method for efficiently separating oily wastewater. In this work, a completely inorganic hierarchical structure made up of a Co and Ni double hydroxide (CoNi–OH) was successfully prepared using a simple one-step in situ method. Combining the unique hierarchical architecture with strong water locking capability, a biomimetic cactus-like hierarchical CoNi–OH-4 coated stainless steel mesh (CoNi–OH-4/SSM) exhibits excellent superhydrophilicity/underwater superoleophobicity and superior anti-oil-fouling capability for high-efficiency oil/water separation with an ultrahigh flux (>37 227 L m−2 h−1) and excellent oil rejection ratio of >99.95%. Continuous lubricating oil/water separation tests demonstrated that CoNi–OH-4/SSM shows high separation capability and excellent recycling over 20 cycles with a stable flux of 37 000 L m−2 h−1 and oil rejection ratio of >99.90%. Furthermore, CoNi–OH-4/SSM exhibits outstanding mechanical, chemical, and long-term stability. Biomimetic CoNi–OH-4/SSM, made using a simple preparation method, has superior anti-oil-fouling properties, excellent oil/water separation performance, and outstanding mechanical and chemical stabilities, revealing its great potential for practical applications in oil/water separation.

Self-powered photodetectors (PDs) have attracted much attention due to their merit of working without an external power source. Performance enhancement is favorable for their development and practical applications. In this work, a clear and compact ZnO crystal shell layer is created on the surface of ZnO nanorods by using a surface lattice reconstruction technique through triethylamine treatment. After surface lattice reconstruction, the self-powered photoresponse performance of the ZnO NRAs/p-Si heterojunction PD was thus significantly improved by 2 orders of magnitude for 365–950 nm broadband light. Under 950 nm light at 2 μW cm−2, the self-powered PD demonstrated an excellent responsivity of ∼5.36 A W−1 and a detectivity of ∼6.99 × 1014 jones. The results indicate that the compact ZnO crystal shell layer reduces surface oxygen vacancies and dangling bonds, improves light absorption and reduces charge carrier recombination. The strategy provides an approach to design and fabricate other metal–oxide–semiconductor-based self-powered PDs with high performance.

As an emerging post-lithium battery technology, aluminum ion batteries (AIBs) have the advantages of large Al reserves and high safety, and have great potential to be applied to power grid energy storage. But current graphite cathode materials are limited in charge storage capacity due to the formation of stage-4 graphite-intercalated compounds (GICs) in the fully charged state. Herein, we propose a new type of cathode materials for AIBs, namely polycyclic aromatic hydrocarbons (PAHs), which resemble graphite in terms of the large conjugated π bond, but do not form GICs in the charge process. Quantum chemistry calculations show that PAHs can bind AlCl4- through the interaction between the conjugated π bond in the PAHs and AlCl4-, forming on-plane interactions. The theoretical specific capacity of PAHs is negatively correlated with the number of benzene rings in the PAHs. Then, under the guidance of theoretical calculations, anthracene, a three-ring PAH, was evaluated as a cathode material for AIBs. Electrochemical measurements show that anthracene has a high specific capacity of 157 mAh g-1 (at 100 mA g-1 ) and still maintains a specific capacity of 130 mAh g-1 after 800 cycles. This work provides a feasible "theory guides practice" research model for the development of energy storage materials, and also provides a new class of promising cathode materials for AIBs.

The discord between the insufficient abundance and the excellent electrocatalytic activity of Pt urgently requires its atomic-level engineering for minimal Pt dosage yet maximized electrocatalytic performance. Here we report the design of ultrasmall triphenylphosphine-stabilized Pt

Black phosphorus (BP) nanosheets have been receiving attention for gas sensing showing superior sensitivity and selectivity among various two-dimensional materials. However, the instability of BP nanosheets due to chemical degradation, especially in humid environments, has severely limited their potential applications. Here, we propose to control the chemical stability of BP nanosheets through modifying their end groups via silanization treatment. Compared with other chemical passivation methods, the end group modification strategy proposed here can be well-controlled and results in little variation in the electronic structure of the puckered phosphorus plane. The results show that modification with fluoroalkylsilane leads the hydrophilic BP to become hydrophobic and exhibits extended chemical stability in oxidizing, humid environments. The sensitivity of fluoroalkylsilane-modified BP (F-BP) to NO2 improved by 3.9-fold in comparison with that of pristine BP nanosheets. More importantly, the NO2 sensing response could remain stable under changing relative humidity ranging from 5% to 95%. Such excellent sensing performance is ascribed to the strong interaction between NO2 and BP decorated with fluoroalkylsilane, as confirmed by density functional theory calculations. This work offers an effective means for preventing degradation of BP in ambient environments and provides a promising solution to solve the issue regarding humidity dependence in gas sensors.

Understanding the effects of pore size on shale gas adsorption behavior is necessary for accurate evaluation of adsorbed gas content under geological conditions. Shale is a porous medium, and the pore structure of the shale reservoir is complicated, with a wide distribution of aperture sizes. Critical parameters for investigating pore size effects on shale gas adsorption behavior were determined, using Grand Canonical Monte Carlo (GCMC) simulations, and the shale gas occurrence state in varying sized kerogen pores was documented, by linking GCMC simulations to the experimental pore size distribution. It was found that using the excess adsorption estimation, in terms of per unit surface area (PUSA), which was obtained from the free gas density calculated by using the GCMC method in a bulk simulation cell, and then derived from the free volume probed by the methane, was a reasonable way of demonstrating pore size effects on shale gas adsorption behavior. The distribution profiles of both the gas density and the interaction energy, rather than their average values, could be used to reflect this pore size effect objectively. Gas density in the adsorption phase rose non-monotonically with reducing pore size, under the combined influence of the interactions’ overlapping effects and the limited pore space, and the overlapping threshold was determined to be 1.24 nm for the experiments. The gas in the pores that were smaller than the overlapping threshold, which was difficult to desorb under geological pressures, accounted for approximately 40.53% of the total adsorbed gas in the kerogen. The adsorbed gas in the kerogen lay mainly (84.97%) in smaller pores ( 5 nm).

It is demonstrated that moderate oxygen vacancies can greatly improve the photo-responsive performance of Zinc oxide (ZnO) nanoparticles thin film/p-Si heterojunctions. The ZnO nanoparticles thin film/p-Si heterojunctions shows a stable, repeatable photo response at 365 nm or 900 nm. Under 900 nm of 0.1 mWcm−2 the sensitivity of device reaches an excellent value of 1.2 × 106 cm2/W, with outstanding detectivity of 3.6 × 1012 cmHz1/2W−1 and ultrahigh responsivity of 3.5 AW-1 at −2 V, and a fast response speed with rising time (∼ms). The comprehensive properties of present device are significantly better than those reported ZnO thick film/Si heterojunctions and even compared with that of some new 2D nanomaterials/Si heterojunctions in all aspects of performance, achieving an optimal balance among all the critical features. The excellent performance of ZnO nanoparticles thin film/p-Si heterojunctions may be attributed to rising Fermi level of ZnO nanoparticles thin film due to moderate oxygen vacancies, the excellent optical absorption characteristics of ZnO nanoparticles thin film and the interface effect between ZnO nanoparticles thin film and Si. This high-performance heterojunctions photodetector should have important prospects for practical applications, and the integration of such metal oxide nanostructures with traditional Si semiconductor would open up great opportunities for next-generation optoelectronic devices.

Li CO2 battery is a very promising power source with high energy density. Its performance is strongly restricted by the cathode catalysts, in which carbon-based catalysts have been mostly investigated up to now. However, the impacting factors on the performance of carbon catalysts is not yet elucidated. Here, we employed a variety of carbon materials with different pore-structure features as the cathode catalysts of Li CO2 batteries to reveal which are the main influencing factor on the catalytic performance of carbon catalysts. It is found that suitable pore shape (most important), large pore size and high surface area are crucial factors to the catalytic performance of carbon catalysts. This finding is of great significance to the further development of Li CO2 batteries.

A hierarchical structured steel mesh decorated with metal organic framework (UiO-66-NH2) nanoparticles/graphene oxide (GO) nanosheets was successfully prepared via a simple self-assemble method. Because water molecules tend to build hydrogen bonds with the amine, carboxyl and hydroxyl functional groups of UiO-66-NH2/GO hierarchical structure, the hierarchical structure can easily capture water and tightly lock the water to build a stable water layer on the steel mesh surface and block oil in contact with the steel mesh. Therefore, the obtained hierarchical structured steel mesh exhibits super-hydrophilicity, underwater super-oleophobicity, excellent oil resistance and outstanding oil/water separation performance with a superior high permeating flux (54,500 L m−2 h−1) and rejection (>99.9%) under gravity force, indicating the mesh possesses great potential for treating oily wastewater.

Conductive borophene nanostructures are proposed as an excellent candidate material for charge-controlled switchable H 2 storage. Based on density functional theory calculations, we investigate the H 2 adsorption on the charged borophene nanosheet. It is found that the adsorption energies of H 2 on either positively or negatively charged borophene nanosheets are dramatically enhanced in compared with the neutral material. Charge modulation strategies therefore offer the potential for spontaneous, controllable H 2 storage and release. Moreover, the positive or negative charging of borophene nanosheets can in principle achieve H 2 storage capacities of 6.5 wt%. These results could provide new insights in searching for materials with exceptionally high H 2 storage capacity.

An environmental-friendly stainless steel mesh (SSM) decorated with polydopamine (PDA) and graphene oxide (GO) for oil/water mixture separation was successfully fabricated via a facile dipping coating method. PDA particles were firstly modified on the mesh surface by the self-polymerization of dopamine. Then, GO was firmly anchored onto the surface of PDA particles through the covalent bonds or electrostatic interaction between GO and PDA. Finally, a SSM/PDA/GO multilevel structure was prepared, which shows superior hydrophilicity and excellent anti-fouling properties due to the hydrophilic functional groups and a thicker water layer confined inside SSM/PDA/GO multilevel structure. Therefore, the as-prepared SSM/PDA/GO mesh with a large oil intrusion pressure (>3 kPa) can separate oil/water mixture with ultra-high flux (∼15,000 L m−2 h−1), preferable separation efficiency (>99.95%) and outstanding recyclability. Furthermore, the SSM/PDA/GO possesses superior stability under harsh environmental conditions, which indicates that the mesh is a promising candidate for practical oil spill cleanup in harsh conditions, especially in high salty marine environment.

A nanofibrous polyacrylonitrile membrane decorated with metal-organic frameworks (MOFs) of UiO-66-NH2 is prepared via a simple and flexible self-assemble method. It is found that the membrane shows high-efficiency separation performance of oil-water emulsions, due to the hydrophilic carboxyl and amino groups of UiO-66-NH2 and the gaps between neighboring UiO-66-NH2. Remarkably, solely driven by gravity (∼0.01 bar), the obtained membrane can effectively separate oil-water emulsions with an excellent separation efficiency (>99%, TOC

Understanding the adsorption mechanisms of different gas molecules on various minerals is crucial for accurately modelling shale gas adsorption behaviors and for objectively evaluating adsorbed gas contents under geological conditions. We simulated the adsorption behaviors of CH4, CO2 and N2 on both organic matter and inorganic minerals at 60 °C and 90 °C over a range of pressures up to 50 MPa by using the Grand Canonical Monte Carlo (GCMC) method. It has been found that both the comprehensive effect of the adsorption sites with differential adsorption capacity and the distribution density of the adsorption sites on the organic matter and inorganic mineral surfaces control the adsorption capacity in terms of per unit surface area of minerals. For individual minerals with a certain adsorption capacity in terms of per unit surface area, the specific surface area of individual minerals is the critical factor that determines the adsorption capacity in terms of per unit mass of the minerals. The interaction among gas molecules also affects the adsorption behavior slightly. We further compared the adsorption capacity among various gas molecules on both organic matter and inorganic minerals by inspecting the strength and distribution density of the adsorption sites on mineral surfaces, the specific surface area of the minerals and the interaction strength among gas molecules. These investigations allowed us to identify the key factors controlling shale gas adsorption mechanisms on different minerals, which provide some helpful insights for both of the exploration and the development of shale gas.

Native defects can degrade the performance and stability of an optoelectric device. Herein, a zeolitic imidazolate framework-8 (ZIF-8)@H:ZnO core–shell nanorod arrays/Si heterojunction self-powered photodetector is demonstrated. Via the combined process of hydrogenation and ZIF-8 passivation, the photoresponsive characteristics of this photodetector could be significantly enhanced; the photodetector exhibited the superior detectivity of ∼2.14 × 1016 Jones (1 Jones = 1 cm Hz1/2 W−1), the high responsivity of ∼7.07 × 104 mA W−1, the prominent sensitivity of ∼2.08 × 1012 cm2 W−1 and broadband photodetection in the region ranging from ultraviolet to near infrared. As a critical figure of merit, its responsivity increased by nearly 5 orders of magnitude than that of the pristine ZnO nanorod arrays/Si heterojunction photodetector. More importantly, the comprehensive performance of the ZIF-8@H:ZnO core–shell nanorod arrays/Si heterojunction photodetector was significantly higher than that of ZnO-based photodetectors reported to date, and it was comparable to those of two-dimensional (2D) materials, zero-dimensional (0D) materials, topological insulators, perovskites and other oxide-based self-powered photodetectors. This novel post-treatment strategy has significant potential for application in the development of high-performance self-powered photodetectors. Moreover, this study may be extended to other oxide-based optoelectronic devices.

Gas production from shale gas reservoirs can be enhanced by increasing the temperature of the reservoirs due to the increased desorption of the adsorbed gas. However, limited techniques are currently available for practically introducing heat into such low permeability reservoirs. This paper investigates the feasibility of an electrical resistance heating method to promote shale gas production by increasing the temperature of the reservoirs. To achieve our research goal, a mechanistic numerical model is developed to describe electrical field, temperature field, and pressure field. To capture gas flow in a shale gas reservoir, non-linear flow, diffusion and adsorption/desorption which are all dependent on temperature are incorporated into a dual continuum media model. In our study, the gas production enhancement by electrical heating with two parallel horizontal electrode wells is evaluated using this model. We then assess impacts of the thermal properties of the formation, electrode length, electrical power, Langmuir volume and starting time of heating on gas production. The results indicate that the electrical heating method using two parallel horizontal electrodes can be an efficient method to enhance shale gas production. The heat capacity and conductivity of the formation have significant impacts on gas production. Reservoirs with low conductivity and low heat capacity tend to produce more gas due to heating. Meanwhile, shale gas reservoirs with high Langmuir volume also tend to yield more gas due to heating for. To maximize gas production, electrical power should be optimized based on the properties of shale gas reservoir and heating equipment. Longer electrodes heat more formations of the reservoir and thus lead to higher gas production by using the electrical heating method. In order to efficiently enhance shale gas production, electrical heating should start later in gas production, instead of earlier.

The organic pollutants, typical of emulsified oils and soluble organic dyes, is commonly found in wastewater, however simultaneous removal of them remains challenging because of their difference in surface charge, molecule size, and solubility in water. Inspired by the water purification of the earth's multilayer strata, a fibrous membrane with multifunctional skin is fabricated by coupling sub-micrometer pores layer of polyaniline (PANI) and nano molecular brush of polyacrylic acid (PAA)/polyethyleneimine (PEI) on polyacrylonitrile membrane, for cross-scale organic pollution/water separation. This ultrathin skin of PANI/PAA/PEI is endowed with sub-micrometer pores and strong hydration, which can effectively prevent tiny oil droplets from entering or adhering the membrane pores. Furthermore, this skin with double electric layer can selectively adsorb and even filtrate anionic/cationic dyes by protonation and deprotonation effect in different pH solutions. The synergy of these features enables this membrane with ultra-high water flux (>3000 L m−2 h−1 bar−1), oil rejection rates (>99.6%), and anionic/cationic dyes adsorbability (>49.1 mg/g). Besides, the membrane also exhibits desirable reusability, excellent mechanical durability and outstanding acid/alkali resistance, promising for removal of insoluble emulsified oils and soluble organic dyes in wastewater.