Enhanced hydrogen generation from Al-water reaction mediated by metal salts

Hydrogen generation by the reaction of micrometer-aluminum powder with water at room temperature is hard to proceed due to the inhibition of alumina layer. In this study, a novel strategy of metal salts mediated Al-water reaction was proposed for more efficient and practical hydrogen generation. The effects of metal salt composition and dosage, and water injection rate and volume on hydrogen generation were investigated. The hydrogen yield of 230.0 mL was achieved in the Al/Ni/Cu/H₂O system within 600 s under the following conditions: 0.24 g aluminum with the molar ratio of Al, Ni and Cu at 10:1:1 and 2 mL water at the injection rate of 2 mL/min, which was equivalent to 70.4% of the theoretical hydrogen yield. Based on the morphology, element composition, crystal structure and electrochemical test results of the obtained composites after reaction, the mechanism of hydrogen production by metal salts mediated Al-water reaction was proposed.     

Single chamber Solid Oxide Fuel Cells selective electrodes: A real chance with brownmillerite-based nanocomposites

In this contribution brownmillerite-based nanocomposite cathode for Single-Chamber Solid Oxide Fuel Cells is developed. These cells can be very attractive especially for small and cheap devices because of the absence of seals. The efficiency of SC-SOFCs is strictly connected to the selectivity of anode and cathode, the bottleneck for this technology. The development of a cathode inert in fuel oxidation is particularly challenging. Our strategy is to start from a catalytically un-active support (CFA = Ca₂FeAl_0.95Mg_0.05O₅) and induce the formation of iron oxide based nanoparticles, expected to activate oxygen. Symmetric (CFA + FeO_x/CGO/CFA + FeO_x) and complete cells (CFA + FeO_x/CGO/Ni-CGO) are studied in air and methane/oxygen 2:1 mixture. The Area Specific Resistance of CFA + FeO_x is less than 1/3 that of CFA. The high selectivity allows to reach an efficiency of 25%; power still needs to be increased but we demonstrated the possibility to develop selective low cost electrodes. The effect of air, methane/oxygen exposure and the heat treatments were carefully investigated.     

Effect of different control strategies on rapid cold start-up of a 30-cell proton exchange membrane fuel cell stack

Many places experience extreme temperatures below −30 °C, which is a great challenge for the fuel cell vehicle (FCV). The aim of this study is to optimize the strategy to achieve rapid cold start-up of the 30-cell stack at different temperature conditions. The test shows that the stack rapidly starts within 30 s at an ambient temperature of −20 °C. Turning on the coolant at −25 °C show stability of the cell voltage at both ends due to the end-plate heating, however, voltage of intermediate cells fluctuates sharply, and successful start-up is completed after 60 s. The cold start strategy changes to load-voltage cooperative control mode when the ambient temperature reduced to −30 °C, the voltage of multiple cells in the middle of the stack fluctuate more drastic, and start-up takes 113 s. The performance and consistency of the stack did not decay after 20 cold start-up experiments, which indicates that our control strategies effectively avoided irreversible damage to the stack caused by freeze-thaw process.     

Cell-envelope proteinases from lactic acid bacteria: Biochemical features and biotechnological applications

Proteins displayed on the cell surface of lactic acid bacteria (LAB) perform diverse and important biochemical roles. Among these, the cell-envelope proteinases (CEPs) are one of the most widely studied and most exploited for biotechnological applications. CEPs are important players in the proteolytic system of LAB, because they are required by LAB to degrade proteins in the growth media into peptides and/or amino acids required for the nitrogen nutrition of LAB. The most important area of application of CEPs is therefore in protein hydrolysis, especially in dairy products. Also, the physical location of CEPs (i.e., being cell-envelope anchored) allows for relatively easy downstream processing (e.g., extraction) of CEPs. This review describes the biochemical features and organization of CEPs and how this fits them for the purpose of protein hydrolysis. It begins with a focus on the genetic organization and expression of CEPs. The catalytic behavior and cleavage specificities of CEPs from various LAB are also discussed. Following this, the extraction and purification of most CEPs reported to date is described. The industrial applications of CEPs in food technology, health promotion, as well as in the growing area of water purification are discussed. Techniques for improving the production and catalytic efficiency of CEPs are also given an important place in this review.     

Bimetallic PtPd nanoparticles relying on CoNiO2 and reduced graphene oxide as a most operative electrocatalyst toward ethanol fuel oxidation

Of late, fuel cells have drawn great attentions owing to high-energy demands, fossil fuel depletion and worldwide environmental pollution. Direct ethanol fuel cell (DEFC) constituted as one of the most promising sources of green energy, howbeit the ethanol oxidation reaction (EOR) sluggish kinetic is one of the essential challenges toward the commercialization of DEFCs. Herein, we introduce bimetallic catalyst on CoNiO₂ modified reduced graphene oxide (rGO) to completely exploit the advantages of nano-surface structures as well as the reduction of Pt and Pd loading in fuel cells. With the combined advantages of PtPd, CoNiO₂ and rGO, a significant enhancement in electrocatalytic behavior, stability and CO poisoning tolerance of PtPd have been observed. Regarding the implications, PtPd/CoNiO₂/rGO is greatly preferable than Pt/CoNiO₂/rGO and Pd/CoNiO₂/rGO in terms of high electroactive surface area (ECSA), electro-catalytic activity, and lower onset potential (E_ons) towards the EtOH oxidation in alkaline media. Furthermore, the chronoamperometry curve (CA) illustrated 77% after 3600 s which is dramatically soared compared with the other electrodes (≤40%), demonstrating the high stability of the PtPd bimetallic nanoparticle electrocatalyst. Ultimately, PtPd/CoNiO₂/rGO nanocomposite is found to be an excellent anode electrocatalyst for application in DEFCs.     

Growth of Ni/Mo/Cu on carbon fiber paper: An efficient electrocatalyst for hydrogen evolution reaction

The exploration of efficient catalysts toward hydrogen evolution reaction (HER) is still an urgent task. In this paper, Ni/Mo/Cu/C and Ni/Mo/C electrode were obtained by conventional pulse voltammetry, which acted as cathode in microbial electrolysis cells (MECs). The prepared samples are analyzed using SEM, XRD, XPS and electrochemical analysis techniques. Results indicated that the Ni/Mo/Cu coating has a rough and globular structure and presents high current density, a lower Tafel slope of 23.9 mV/dec than 30 mV/dec of Pt, which exceeds the electrochemical activity of Pt electrode. Its remarkably enhanced electrocatalytic activity is attributed to the high surface area, high conductivity as well as synergistic interaction among Ni, Mo and Cu.     

Recent advances in two-dimensional Pt based electrocatalysts for methanol oxidation reaction

Direct methanol fuel cells (DMFCs) had been attracted considerable attention for its advantages of high energy density, simplified systems and readily transportation and storage of methanol. However, the notoriously sluggish kinetics of methanol oxidation reaction (MOR) of the anode reaction, had greatly affected the commercialization of DMFCs. On one hand, Pt based catalyst are still the most effective MOR catalysts, while the high cost caused by the high loadings of electrocatalyst to compensate the low MOR activity impedes the wide accessible of DMFCs. In addition, the occurrence of catalyst poisoning owing to the strong interaction between Pt and carbon monoxide (CO) generated during the MOR processing, further leading to the fast decay in the performance and stability of MOR electrocatalysts. Two-dimensional (2D) Pt based nanostructures is regarded to be one promising and effective class of MOR electrocatalysts, and attracted much attention due to the high electron mobility, highly exposed active sites, and extraordinary thermal conduction. In this review, the mechanism of MOR was firstly introduced, and then the synthesis conditions, structure characteristics and methanol oxidation performances both in acidic and alkaline dielectric of 2D Pt based nanocatalysts were introduced. Subsequently, we briefly analyzed the structural characteristics of 2D Pt based nanocatalysts and their advantages, including the low platinum loadings, high specific surface area and majority of atomic active sites exposed. Finally, the opportunities and challenges for designing of advanced 2D Pt based nanocatalysts was proposed and discussed.     

Development and performance assessment of new solar and fuel cell-powered oxygen generators and ventilators for COVID-19 patients

In this study, a new solar-based fuel cell-powered oxygenation and ventilation system is presented for COVID-19 patients. Solar energy is utilized to operate the developed system through photovoltaic panels. The method of water splitting is utilized to generate the required oxygen through the operation of a proton exchange membrane water electrolyser. Moreover, the hydrogen produced during water splitting is utilized as fuel to operate the fuel cell system during low solar availability or the absence of solar irradiation. Transient simulations and thermodynamic analyses of the developed system are performed by accounting for the changes in solar radiation intensities during the year. The daily oxygen generation is found to vary between 170.4 kg/day and 614.2 kg/day during the year. Furthermore, the amount of daily hydrogen production varies between 21.3 kg/day and 76.8 kg/day. The peak oxygen generation rate attains a value of 18.6 g/s. Moreover, the water electrolysis subsystem entails daily exergy destruction in the range of 139.9–529.7 kWh. The maximum efficiencies of the developed system are found to be 14.3% energetically and 13.4% exergetically.     

Single-step inkjet-printed paper-origami arrayed air-breathing microfluidic microbial fuel cell and its validation

Microfluidic paper based microbial fuel cells (μP-MFCs) have gained considerable popularity due to their compact, quick and low-cost fluid manipulation paradigm. Compared to conventional technologies, paper as a substrate with advanced nanomaterial electrode material has many distinct advantages from point-of-care monitoring to energy harvesting. As a result, these have been used and are more popular in a variety of fields, such as health diagnostics, environmental and food quality management. By this encouragement, herein a portable microbial fuel cell as an origami array has been demonstrated using custom carbon electrodes with a modified the transition metal oxide MnO₂ nanomaterial. This customized electrode design was first printed using a tabletop PCB inkjet printer where the anode was further modified with synthesized MnO₂ nanoparticles. The entire cell was formed by folding the paper along predefined edges where the fuel, Shewanella putrefaciens, was streamed continuously via inherent capillary cation. Various studies, such as morphological, surface catalyst coating, amount loading and volumetric culture optimization experiments, have also been accomplished to find the most appropriate optimum parameter to enhance power conversion efficiency. The developed origami arrayed microbial fuel generated an open-circuit potential (OCP) for two parallel connected MFCs of 0.534 V and a maximum power density of 15.9 μW/cm² with a maximum current density of 130 μA/cm². In the end, the harvested power was used by powering the digital watch circuit through the ultra-low DC-DC booster board. Such an MFC origami array, with simple electrode manufacturing and modification process, has a great potential and bright future in Internet of Things (IoT) applications by making multiple stacks where the data can be monitored.