Integrating hydrogen generation and storage in a novel compact electrochemical system based on metal hydrides

A novel electrochemical system has been developed which integrates hydrogen production, storage and compression in only one device, at relatively low cost and high efficiency. The development of efficient and reliable energy storage systems based on hydrogen technology represents a challenge to seasonal storage based on renewable hydrogen. State of the art renewable energy generation systems include separate units such as electrolyser, hydrogen storage vessel and a fuel cell system for the conversion of H2 back into electricity, when required. In this work, a compact unit integrating production and storage is proposed. The developed prototype comprises a six electrode cell assembly using an AB5 type metal hydride and Ni plates as counterelectrodes, in a 35 wt% KOH solution. During charging, hydrogen is absorbed in the metal hydride and corresponding oxygen is conveyed out of the system. Conversely, in the case of discharging hydrogen stored in the metal hydride is released to an external H2 storage. In the present prototype, released hydrogen was delivered into the hydrogen storage up to a pressure of 15 Bar. Metal hydride electrodes with chemical composition LaNi4.3Co0.4Al0.3 were prepared by high frequency vacuum melting followed by high temperature annealing at 1000O C during 8 hours. X-Ray phase analysis showed typical hexagonal structure and no traces of other intermetallic compounds belonging to the La-Ni phase diagram. Thermodynamic study has been performed in a Sieverts type of apparatus produced by Labtech. Int. During cycling, charging was run at 40 A at cell voltages of 1.7 V for two hours which corresponds to C/2 charging time. Hydrogen was released by applying a constant current of 40A for two hours until cell voltage rise from 0.5 to 1.7V, at the end of the processes. The process was studied in-situ using a gas chromatograph from Agilent. It is anticipated that the device will be integrated as a combined hydrogen generator and storage unit in a stand alone system associated to a 1 kW fuel cell

Novel hydrogen generator: storage based on metal hydrides

A novel electrochemical system has been developed which integrates hydrogen production, storage and compression in only one device, at relatively low cost and high efficiency. The prototype comprises a six electrode cell assembly using an AB5 type metal hydride and Ni plates as counter electrodes, in a KOH solution. Metal hydride electrodes with chemical composition LaNi4.3Co0.4Al0.3 has been prepared by high frequency vacuum melting followed by high temperature annealing. X-Ray phase analysis showed typical hexagonal structure and no traces of other intermetallic compounds belonging to the La-Ni phase diagram. Thermodynamic study of the alloy has been performed in a Sieverts type apparatus produced by Labtech. Ltd. In the present prototype during charging, hydrogen is absorbed in the metal hydride and corresponding oxygen is conveyed out of the system. Conversely, in the case of discharging the hydrogen stored in the metal hydride it is released to an external H2 storage. Released hydrogen is delivered into the hydrogen storage up to a pressure of 15 bar. In this work, a compact unit integrating production, storage and compressing hydrogen is proposed as one device at relatively low cost and higher efficiency than a classical electrolyser. It is anticipated that the device will be integrated as a combined hydrogen generator in a stand alone system associated to a 1 kW fuel cell

The evolutionary signal in metagenome phyletic profiles predicts many gene functions

Background. The function of many genes is still not known even in model organisms. An increasing availability of microbiome DNA sequencing data provides an opportunity to infer gene function in a systematic manner. Results. We evaluated if the evolutionary signal contained in metagenome phyletic profiles (MPP) is predictive of a broad array of gene functions. The MPPs are an encoding of environmental DNA sequencing data that consists of relative abundances of gene families across metagenomes. We find that such MPPs can accurately predict 826 Gene Ontology functional categories, while drawing on human gut microbiomes, ocean metagenomes, and DNA sequences from various other engineered and natural environments. Overall, in this task, the MPPs are highly accurate, and moreover they provide coverage for a set of Gene Ontology terms largely complementary to standard phylogenetic profiles, derived from fully sequenced genomes. We also find that metagenomes approximated from taxon relative abundance obtained via 16S rRNA gene sequencing may provide surprisingly useful predictive models. Crucially, the MPPs derived from different types of environments can infer distinct, non-overlapping sets of gene functions and therefore complement each other. Consistently, simulations on > 5000 metagenomes indicate that the amount of data is not in itself critical for maximizing predictive accuracy, while the diversity of sampled environments appears to be the critical factor for obtaining robust models. Conclusions. In past work, metagenomics has provided invaluable insight into ecology of various habitats, into diversity of microbial life and also into human health and disease mechanisms. We propose that environmental DNA sequencing additionally constitutes a useful tool to predict biological roles of genes, yielding inferences out of reach for existing comparative genomics approaches

A sodium borohydride hydrogen generation reactor for stationary applications: Experimental and reactor simulation studies

Ruthenium on nickel-foam catalyst was prepared for hydrogen production from the hydrolysis reaction of an alkaline NaBH4 solution. Experiments were carried out at five temperatures (30, 40, 45, 50 and 60 °C) in a 0.1 dm3 small batch reactor. To understand the kinetic behaviour of the hydrolysis reaction in the presence of this catalyst, the experimental data were fitted to three kinetic models (zero-order, first-order and Langmuir–Hinshelwood) using the integral method. Results showed that Langmuir–Hinshelwood model described fairly well the reaction for all tested temperatures and for the entire time range. Zero-order could be applied only at low temperatures or until the concentration of NaBH4 remained high in the solution; first-order could be only applied efficiently at 60 °C. In addition to the kinetic study, a dynamic, three dimensional and non-isothermal model was developed to describe a pilot scale reactor for stationary use. The experimental data was used to validate the numerical model which was developed using a commercial solver software. All relevant transport phenomena were treated in detail and the kinetic model developed previously was introduced into the algorithm. Results showed that the reaction rate was extremely affected by the mass transport resistance of sodium borohydride from the bulk to the catalyst surface

Exploring As-Cast PbCaSn-Mg anodes for improved performance in copper electrowinning

Lead calcium tin (PbCaSn) alloys are the common anodes used in copper electrowinning (Cu EW). Given a large amount of energy consumed in Cu EW process, anodes with controlled oxygen evolution reaction (OER) kinetics and a lower OER overpotential are advantageous for reducing the energy consumption. To date, magnesium (Mg) has never been studied as an alloying element for EW anodes. As-cast PbCaSn anodes with the addition of Mg were examined herein, revealing an improved performance compared to that of the industrial standard PbCaSn anode. The alloy performances in the early stages of anode life and passivation were established from electrochemical studies which were designed to simulate industrial Cu EW process. The 24-hour polarization testing revealed that the Mg alloying depolarizes the anode potential up to 80 mV; thus, resulting in a higher Cu EW efficiency. In addition, scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the alteration of the alloy microstructure and the corresponding interfacial reactions contribute to the changes of the anode electrochemical performances. The present study reveals for the first time the potency of Mg alloying in reducing the overpotential of PbCaSn anode