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The functional microporous layer, acting as a mass-transfer control medium with a rational structure and surface morphology as well as high electrical conductivity, significantly affects the performance of micro-direct methanol fuel cells (μDMFCs). Bioinspired by the architecture and multi-functional properties of mangrove roots, this study develops a simple and versatile strategy based on magnetron sputtering and chemical vapor deposition to fabricate a mangrove root-inspired carbon nanotube film (MR-CNTF) as the functional interface in μDMFCs. It has features such as ultralightweight, high porosity, and good electrical conductivity. During the synthesis process, an apex-growth model of CNTF is identified. The results indicate that the MR-CNTF used as a cathodic microporous layer can remarkably facilitate the oxygen transport and water management. Because of its multi-functional structure and excellent material characteristics, the passive μDMFC displays a peak power density of 14.9 mW cm

The lithium-ion battery (LIB) is an efficient electrochemical energy storage device with high voltage, long life, good safety, etc. Silicon has a high theoretical specific capacity (4200 mA h g−1), due to which it is considered a promising anode material for next-generation LIBs. However, the huge volume change (400%) of the Si material during the lithiation/delithiation processes destroys its structure, which greatly reduces the initial coulombic efficiency, cycle stability and rate performance of the battery. Accordingly, constructing nanostructured Si, particularly silicon nanowires (SiNWs), can help to address the above issues. Additionally, it is important to further improve the electrochemical performance by incorporating some additives in SiNW-based electrodes. Therefore, this review focuses primarily on SiNW-based materials as anodes for LIBs from a material-based perspective. Various materials incorporated into SiNW-based anodes through doping or compositing are reported. The electrochemical effects of diverse additives, including carbon materials, metals, metal oxides, polymers, Si-based materials and other special substances, are comprehensively reviewed.

Lithium-ion batteries (LIBs) play an important role in modern society. The low capacity of graphite cannot meet the demands of LIBs calling for high power and energy densities. Silicon (Si) is one of the most promising materials instead of graphite, because of its high theoretical capacity, low discharge voltage, low cost, etc. However, Si shows low conductivity of both ions and electrons and exhibits a severe volume change during cycles. Fabricating nano-sized Si and Si-based composites is an effective method to enhance the electrochemical performance of LIB anodes. Using a small size of Si nanoparticles (SiNPs) is likely to avoid the cracking of this material. One critical issue is to disclose different types and electrochemical effects of various coupled materials in the Si-based composites for anode fabrication and optimization. Hence, this paper reviews diverse SiNP-based composites for advanced LIBs from the perspective of composition and electrochemical effects. Almost all kinds of materials that have been coupled with SiNPs for LIB applications are summarized, along with their electrochemical influences on the composites. The integrated materials, including carbon materials, metals, metal oxides, polymers, Si-based materials, transition metal nitrides, carbides, dichalcogenides, alloys, and metal-organic frameworks (MOFs), are comprehensively presented.

In this study, a laser micro-milling technique was introduced into the fabrication process of surface microchannels with different geometries and dimensions on the porous copper fiber sintered felts (PCFSFs). The PCFSFs with surface microchannels as catalyst supports were then used to construct a new type of laminated methanol steam reforming microreactor for hydrogen production. The microstructure morphology, pressure drop, velocity and permeability of PCFSF with surface microchannels were studied. The effect of surface microchannel shape (rectangular, stepped, and polyline) and catalyst loading amount on the reaction performance of methanol steam reforming microreactor for hydrogen production was further investigated. Our results show that the PCFSF with rectangular microchannels demonstrated a lower pressure drop, higher average velocity and higher permeability compared to the stepped and polyline microchannel. Furthermore, the PCFSF with rectangular microchannels also exhibited the highest methanol conversion and H2 flow rate. The best reaction performance of methanol steam reforming microreactor for hydrogen production was obtained using PCFSF with rectangular microchannels when 0.5 g catalyst was loaded.

To realize the integration and amplification of microreactors, this paper chose the methanol steam reforming microreactor for hydrogen production as the research object and adopted copper foam as the catalyst support. Three types of microreactors were designed with different structure sizes (small [S-type], medium [M-type], and large [L-type]), and reaction units were assembled in series and in parallel. The reaction performance of the methanol steam reforming microreactor was studied by varying the gas hourly space velocity (GHSV) and reaction temperature. Results show that the structure size had a large influence on the reaction performance of microreactor. The S-type and M-type microreactors exhibited better reaction performance for hydrogen production, whereas the L-type microreactor had lower reaction performance (methanol conversion decreased by 7.5% and the H2 flow rate decreased by 8.3% compared to the S-type microreactor). The series and parallel assembly methods also demonstrated a clear influence on the reaction performance of the microreactor for hydrogen production. The methanol conversion and H2 flow rate of the series-assembled microreactor decreased clearly, whereas the methanol conversion of the parallel-assembled microreactor changed negligibly. The H2 flow rate of microreactor was exponentially increased by the number of reaction units, and basically no amplification effect existed, making it suitable for integrated amplification of microreactors.

Methanol steam reforming inside micro-reactors is considered as one of the effective approaches for on-board supplying hydrogen for fuel cells. Porous copper fiber sintered felts (PCFSFs) are a new kind of catalyst support for micro-reactors developed in recent years. However, there is a lack of approach to control their porosity configurations due to their random structure. A two-step optimization method was proposed to optimize the PCFSFs’ porosity configuration. Firstly, the topology structures of PCFSFs were optimized based on the best flow distributions obtained from macroscopic numerical analyses, and two kinds of PCFSFs with twelve porosity distributions were fabricated through the multi-step mold pressing and solid-phase sintering method. Secondly, the porosity distributions of the semi-optimized PCFSFs were optimized by investigating their reaction characteristics under different gas hourly space velocities (GHSVs) and reaction temperatures. The results indicated that PCFSFs with porosity distribution along the Left-Right direction (PCFSF-LRs) exhibited better reaction performance than PCFSFs with porosity distribution along the Upside-Underside direction (PCFSF-UUs). The methanol conversion and H2 flow rate for the PCFSF-LRs with porosity distribution of 0.7–0.9–0.8 and 0.8–0.9–0.7 kept on a high level (above 92% and 0.59 mol/h, respectively), regardless of the change of GHSVs and reaction temperatures in most cases. The H2 selectivity of the PCFSF-LR of 0.7–0.9–0.8 was the highest under large GHSVs and all tested reaction temperatures. The demonstrated effect of counteracting, even reversing the conventional influence of the GHSV and temperature on the performance of methanol steam reforming may be attributed to the more uniform flow distribution in the two PCFSF-LRs.

In this study, the porous Cu-Al fiber sintered felt (PCAFSF) was fabricated by low temperature solid-phase sintering method. The laminated PCAFSF as the catalyst support was used for cylindrical methanol steam reforming microreactor for hydrogen production. The two-layer impregnation method was employed to coat the Cu/Zn/Al/Zr catalyst on the PCAFSF. The material composition, specific surface area and catalyst loading of PCAFSF were also measured. The effect of the fiber material, surface morphology and porosity on the reaction performance of methanol steam reforming microreactor for hydrogen production was further investigated. Our results show that the PCAFSF demonstrated much higher methanol conversion and H2 flow rate compared to the porous Cu fiber sintered felt (PCFSF) and porous Al fiber sintered felt (PAFSF) having the same porosity. Furthermore, the rough PCAFSF showed much higher methanol conversion and H2 flow rate compared to the smooth PCAFSF. In case of the PCAFSF, the methanol conversion and H2 flow rate were increased with the decrease of Cu fiber weight and the increase of Al fiber weight. The best reaction performance of microreactor for hydrogen production was obtained using the three layer PCAFSFs with 80% porosity and 1.12 g Cu fiber/1.02 g Al fiber.

Structured PdZnAl/Cu fiber catalyst prepared by a PVA(Polyvinyl Alcohol)-assisted coating method, was integrated in the micro-reactor for methanol steam reforming (MSR), which could be used to efficiently produce hydrogen in situ for a coupled fuel cell. XRD, SEM-EDX and HRTEM etc. were employed to characterize both the fresh and spent powder and structured catalysts. A variety of reaction conditions were tested to achieve the optimized reaction condition, where the H 2 productivity and the product distribution especially CO selectivity were carefully examined. Compared to the structured CuZnAlZr/Cu fiber catalyst, the PdZnAl/Cu counterpart exhibits superior stability in MSR process, and its spent catalyst could be readily regenerated just by oxidation in air at 420 °C for 4 h.

Surface-pattern engineering, as a key strategy to fabricate high-performance Nafion membranes for fuel cells, plays an important role in surface functionalization of the membrane, optimization of the three-phase boundary, water management, proton transport, etc. Considerable efforts have been dedicated to developing advanced-patterned Nafion membranes with single-scale (nanoscale or microscale) and multiscale-patterned structures which are believed to improve the performance of membrane electrode assemblies (MEAs) for fuel cells. In this review, the recent progress in surface-patterned Nafion membranes (SPNMs) equipped with single-scale-patterned structures (including nanostructured and microstructured Nafion membranes) is firstly highlighted. The structural features and construction methods of SPNMs are discussed in detail. The effects of single-scale SPNMs on the construction and performance of fuel cells are also analyzed. Followed is an overview of the recent advances in fabricating multiscale SPNMs based on different strategies with a specific introduction on the membrane related effects on fuel cells. Finally, the future development direction and certain perspectives on the current issues of SPNMs are presented.

Porous copper fiber sintered sheets (PCFSS) as wick are fabricated for loop heat pipes (LHP) using low-temperature solid-phase sintering technology and smooth and rough copper fiber as the manufacturing material. The operational characteristics of LHP with varied wick surface morphologies and filling ratios are analyzed. This study focuses on evaluating the following characteristics: thermal resistance characteristics under increasing and decreasing heat load patterns, evaporator surface thermal homogeneity, thermal inertia, and limit operational characteristics. Experimental results demonstrated that LHP with rough PCFSS exhibited lower thermal resistance. As compared to decreasing heat load conditions, relatively lower thermal resistance of LHP under increasing heat load conditions was obtained. The evaporator surface thermal homogeneity yielded improvement with rough PCFSS and increased filling ratio. A larger thermal inertia of LHP was observed when the low filling ratio was applied, and it will be improved when the filling ratio was increased and the smaller heat load variation intensity was selected. When rough PCFSS wick with 70% porosity and a deionized water filling ratio of 30% were selected, the LHP was able to effectively operate under 5–200 W heat load conditions and yielded prompt response to heat load variation.

In this study, the cascading metal foams were used as catalyst supports for constructing a new type of cylindrical laminated methanol steam reforming microreactor for hydrogen production. The two-layer impregnation method was used to load the Cu/Zn/Al/Zr catalysts, and the ultrasonic vibration method was then employed to investigate the loading performance of metal foams with different types and thicknesses. Furthermore, the effect of the type of catalyst placement, pores per inch (PPI) and foam type on the performance of methanol steam reforming microreactor was studied by varying the gas hourly space velocity (GHSV) and reaction temperature. Compared with two other types of catalyst placement studied, the microreactor containing catalyst-loaded metal foams without clearance cascading (3 × 2) showed the highest hydrogen production performance. When the PPI of the metal foam was increased from 50 to 100, both the methanol conversion and the H2 flow rate gradually increased. Our results also showed that a microreactor with Cu foam as a catalyst support exhibits increased hydrogen production and higher stability than those of a microreactor with Ni foam.

To optimise methanol steam reforming performance of cylindrical microreactor for hydrogen production, an error backpropagation algorithm was used to build a mathematical model for reaction performance of different microreactors for hydrogen production. Additionally, a genetic algorithm (GA) was utilised to process the computational model to obtain the optimum reaction parameters. The reliability of optimum reaction parameters of cylindrical microreactor for hydrogen production was verified by experiments. Firstly, take platemicroreactor as an example, the porosity of porous copper fiber sintered sheet (PCFSS), reaction temperature of methanol steam reforming for hydrogen production, injection velocity of the methanol and water mixture, and catalyst loading of PCFSS were considered as input data, whereas methanol conversion was used as output data. The computational model for specific testing system was gained by utilising input and output data from specific testing system to train the mathematical model for different microreactors, combining with matrix laboratory (MATLAB) neural network toolbox and designed MATLAB program. The Emax of 5% for plate microreactor and Emax of 3.2% for cylindrical microreactor verified the good predictive ability and reliability of the computational model for plate and cylindrical microreactor, indicating the reliability and universal applicability of the mathematical model for different microreactors. Secondly, the effects and mechanisms of PPI, reaction temperature, injection velocity, and catalyst loading on methanol conversion were studied, relying on the computational model. Finally, the optimum reaction parameters were acquired using GA, MATLAB neural network toolbox and designed MATLAB program. The validity of the optimum reaction parameters of cylindrical microreactor for hydrogen production was confirmed by experiments. This study provides a feasible method for methanol steam reforming performance optimisation for hydrogen production.

As environmentally friendly and high-energy density rechargeable energy storage devices, lithium-ion batteries (LIBs) have thriving prospects in the field of energy. The current collector, which serves as an important component of LIBs, significantly influences the electrochemical performance of the battery. Numerous efforts have been spent on the design and fabrication of high-performance negative current collectors in the field of LIBs to achieve excellent battery performances. These high-performance current collectors are mostly structuralized to achieve special functions. Hence, different types of structuralized current collectors used for LIB anodes are comprehensively discussed and summarized in this paper. The structuralized current collectors used in LIB anodes are classified into planar-plate-based special-surface current collectors and the 3D framework-based porous current collectors. Both types of the structuralized current collectors are further divided into the single-component and multicomponent current collectors. More subsections are provided and focus on providing description of the developing strategies, fabrication methods, electrochemical behaviors, in-depth reasons for high performances, and advantages and challenges for real applications of the structuralized current collectors in detail. Subsequently, the challenges and future research directions of structuralized anode current collectors are reasonably clarified. Based on an objective summary of the high-performance negative current collectors, this review provides an enlightening guide for the future development of current collectors and LIBs. The fundamental conclusions can also be extended to other energy storage devices.

Management of the produced carbon dioxide (CO2) is important to improve the performance of a liquid-feed direct methanol fuel cell (DMFC). This work investigates the CO2 bubble behaviors and the two-phase flow characteristics, using a single sinusoidal corrugated channel as the anode flow field. The magnitude and gradient of the fluid velocity in this channel is higher than the traditional straight pattern, as proven by tracking CO2 bubbles. The use of high magnitude and gradient of velocity enhances CO2 emission and fuel delivery, as well as increases the pressure drop. The vortices in the disturbance structure of the corrugated channel help uniformly deliver the reactants and separate bubbles away from the channel wall. Using excessive values of amplitude A and angular frequency W in the corrugated channel causes serious bubble deformation and extra energy consumption. The effect of disturbance structure is negligible with small values of these two parameters. The cell with a corrugated channel shows a higher performance at different feed rates and concentrations of the methanol fuel. The optimal value of A and W are respectively 0.1and 5. The visualization tests demonstrate that the appearance of CO2 bubbles in the corrugated channel is consistent with the simulation results.