Due to its high CO tolerance, the high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) has a simpler fuel processing than a low-temperature polymer electrolyte fuel cell (LT-PEMFC) system.In this study, a performance of the HT-PEMFC integrated with a glycerol steam reformer system with/without a water gas shift reactor is examined and compared with the LT-PEMFC system.The HT-PEMFC system shows good performance over the LT-PEMFC system at the operational condition of high current density condition (>6000 A/m 2 ).The presence of high CO concentration is the main problem of operation of HT-PEMFC system without the water gas shift reactor at high current density.At the same time, the LT-PEMFC suffers from CO poisoning and low oxygen concentration at high current density as well.Considering the system efficiency, the HT-PEMFC system with the water gas shift reactor in the glycerol processor shows the highest overall system efficiency.

Many factors affect the performance of microbial fuel cells (MFCs). Considerable attention has been given to the impact of cell configuration and materials on MFC performance. Much less work has been done on the impact of the anode microbiota, particularly in the context of using complex substrates as fuel. One strategy to improve MFC performance on complex substrates such as wastewater, is to pre-enrich the anode with known, efficient electrogens, such as Geobacter spp. The implication of this strategy is that the electrogens are the limiting factor in MFCs fed complex substrates and the organisms feeding the electrogens through hydrolysis and fermentation are not limiting. We conducted a systematic test of this strategy and the assumptions associated with it. Microbial fuel cells were enriched using three different substrates (acetate, synthetic wastewater and real domestic wastewater) and three different inocula (Activated Sludge, Tyne River sediment, effluent from an MFC). Reactors were either enriched on complex substrates from the start or were initially fed acetate to enrich for Geobacter spp. before switching to synthetic or real wastewater. Pre-enrichment on acetate increased the relative abundance of Geobacter spp. in MFCs that were switched to complex substrates compared to MFCs that had been fed the complex substrates from the beginning of the experiment (wastewater-fed MFCs - 21.9 ± 1.7% Geobacter spp.; acetate-enriched MFCs, fed wastewater - 34.9 ± 6.7% Geobacter spp.; Synthetic wastewater fed MFCs – 42.5 ± 3.7% Geobacter spp.; acetate-enriched synthetic wastewater-fed MFCs - 47.3 ± 3.9% Geobacter spp.). However, acetate pre-enrichment did not translate into significant improvements in cell voltage, maximum current density, maximum power density or substrate removal efficiency. Nevertheless, coulombic efficiency (CE) was higher in MFCs pre-enriched on acetate when complex substrates were fed following acetate enrichment (wastewater-fed MFCs – CE = 22.0 ± 6.2%; acetate-enriched MFCs, fed wastewater – CE =58.5 ± 3.5%; Synthetic wastewater fed MFCs – CE = 22.0 ± 3.2%; acetate-enriched synthetic wastewater-fed MFCs – 28.7 ± 4.2%.) The relative abundance of Geobacter ssp. and CE represents the average of the nine replicate reactors inoculated with three different inocula for each substrate. Efforts to improve the performance of anodic microbial communities in MFCs utilizing complex organic substrates should therefore focus on enhancing the activity of organisms driving hydrolysis and fermentation rather the terminal-oxidizing electrogens.

This study investigated the advantages of using low-cost polyaniline-fabricated stainless steel fiber felt anode-based microbial fuel cells (PANI-SSFF-MFCs) for azo dye acid blue 29 (AB29) containing wastewater treatment integrated with an aerobic bioreactor. The findings of electrochemical impedance spectroscopy (EIS) and polarization studies showed that the PANI–SSFF anode considerably decreased the MFC internal resistance. The highest power density of 103 ± 3.6 mW m−2 was achieved by PANI-SSFF-MFCs with a decolorization efficiency of 93 ± 3.1% and a start-up time of 13 days. The final chemical oxygen demand (COD) removal efficiencies for integrated PANI–SSFF–MFC–bioreactor and SSFF–MFC–bioreactor set-ups were 92.5 ± 2% and 80 ± 2%, respectively. Based on 16S rRNA gene sequencing, a substantial microbial community change was observed in MFCs. The majority of sequences were from the Proteobacteria phylum, accounting for 72% and 55% in PANI–SSFF–anodic biofilm and suspension, respectively, and 58 and 45% in SSFF–anodic biofilm and suspension, respectively. The relative abundance of the seven most abundant genera (Pseudomonas, Acinetobacter, Stenotrophomonas, Geothrix, Dysgonomonas, Shinella, and Rhizobiales) was higher in PANI–SSFF–MFCs (46.1% in biofilm and 55.4% in suspension) as compared to SSFF–MFC (43% in biofilm and 40.8% in suspension) which predominantly contributed to the decolorization of AB29 and/or electron transfer. We demonstrate in this work that microbial consortia acclimated to the MFC environment and PANI-fabricated anodes are capable of high decolorization rates with enhanced electricity production. A combined single-chamber MFC (SMFC)-aerobic bioreactor operation was also performed in this study for the efficient biodegradation of AB29.

This article provides an introduction to the science and technology spanning the electrochemical hydrogen generation and fuel cell sectors. The chapter presents an introduction to hydrogen, its discovery and early electrochemical studies and physical properties and an overview of hydrogen and fuel cell technology. The fundamental background electrochemical science behind hydrogen systems is described. An overview of electrolyzers for hydrogen generation and fuel cells technology is presented with a summary of their current status and developments. Information and examples of existing hydrogen production and fuel cell technologies, and an overview of infrastructure aspects such as hydrogen storage and delivery is provided.

A microbial electrolysis cell (MEC) fully catalysed by microorganisms is an attractive technology because it incorporates the state-of-the-art concept of converting organic waste to hydrogen with less external energy input than conventional electrolysers. In this work, the impact of the anode feed mode on the production of hydrogen by the biocathode was studied. In the first part, three feed modes and MEC performance in terms of hydrogen production were evaluated. The results showed the highest hydrogen production under the continuous mode (14.6 ± 0.4), followed by the fed-batch (12.7 ± 0.4) and batch (0 L m-2 cathode day-1) modes. On one hand, the continuous mode only increased by 15% even though the hydraulic retention time (HRT) (2.78 h) was lower than the fed-batch mode (HRT 5 h). A total replacement (fed-batch) rather than a constant mix of existing anolyte and fresh medium (continuous) was preferable. On the other hand, no hydrogen was produced in batch mode due to the extensive HRT (24 h) and bioanode starvation. In the second part, the fed-batch mode was further evaluated using a chronoamperometry method under a range of applied cell voltages of 0.3-1.6 V. Based on the potential evolution at the electrodes, three main regions were identified depending on the applied cell voltages: the cathode activation (<0.8 V), transition (0.8-1.1 V), and anode limitation (>1.1 V) regions. The maximum hydrogen production recorded was 12.1 ± 2.1 L m-2 cathode day-1 at 1.0 V applied voltage when the oxidation and reduction reactions at the anode and cathode were optimal (2.38 ± 0.61 A m-2). Microbial community analysis of the biocathode revealed that Alpha-, and Deltaproteobacteria were dominant in the samples with >70% abundance. At the genus level, Desulfovibrio sp. was the most abundant in the samples, showing that these microbes may be responsible for hydrogen evolution.

Poly ionic liquids (ILs), also known as polymeric ILs, are a particular class of polymers since they acquire conventional features of polymers and keep some unique characteristics of ILs, including high thermal and electrochemical stabilities and good ionic conductivity. Either IL's cation or anion can constitute the backbone of poly ILs with free mobile anion or cation, respectively. Therefore, unlike inert polymers, poly ILs are considered as charged polymers. Thus, increasing research efforts are devoted to employing poly ILs in many advanced electrochemical applications like fuel cells and batteries. The present review article concentrates on the applications of poly ILs in polymer electrolyte membrane fuel cells (PEMFCs). Firstly, a review of the different approaches to applying poly ILs in polymer electrolyte membranes (PEMs) is introduced. Also, associated properties of poly ILs membranes, such as mechanical properties, conductivity, and thermal stability are described. In addition, an assessment of their performance in PEMFC is included. Secondly, the contributions of poly ILs in improving the cathodic oxygen reduction reaction (ORR) of PEMFC either as an ionomer or a cathodic catalyst layer modified with poly IL are reviewed. Recommendations and future outlooks for improved usage and employment of poly ILs in PEMFCs are presented.

Recently, increasing research attention has been devoted to protic ionic liquids (ILs) because of their versatile properties. Protic ILs are ideal electrolytes for proton exchange membrane fuel cells (PEMFCs) owing to their high proton conductivity, that does not rely on water, and their excellent electrochemical and thermal stabilities. Therefore, they can extend the operating temperature of PEMFCs above 100 degrees C, which is important to raise their effectiveness and efficiency. However, to be employed as polymer electrolyte membranes (PEMs) in PEMFCs, protic ILs are preferred to be in solid films; therefore, several polymers have been blended with different protic ILs to form various PEMs. This review article provides a comprehensive literature survey for protic IL/polymer blends applied as PEMs in PEMFCs. In particular, five conventional polymers combined with protic ILs as PEMs are discussed in detail; Nafion, polybenzimidazole (PBI), poly(vinylidene fluoride-co-hexafluoropropene) (PVdF-HFP), sulfonated polyimide (SPI), and sulfonated poly(ether ether ketone) (SPEEK). Also, some other polymers used in PEMs based on protic ILs are studied to provide comprehensive coverage for all research ideas developed in this topic. Finally, this review addresses the current challenges facing the development of this promising category of PEMs and the recommended research directions that need more investigation.

Aprotic lithium-oxygen batteries currently suffer from poor cyclic stability and low achievable energy density. Herein, gold nanoparticles capped with mercaptosuccinic acid are dispersed in 1.0 M LiClO4/dimethyl sulfoxide (DMSO) as a novel electrolyte for lithium-oxygen batteries. Morphological and electrochemical analyses indicate that film-like amorphous lithium peroxide is formed using the gold nanocolloid electrolyte instead of bulk crystals in battery discharging, which apparently increases the conductivity and accelerates the decomposition kinetics of discharge products in recharging, accompanied by the release of incorporated gold nanoparticles with the decomposition of lithium peroxide into the electrolyte. Experiments and theoretical calculations further demonstrate that the suspended gold nanoparticles in the electrolyte can adsorb some intermediates generated by an oxygen reduction reaction, which effectively alleviates the cleavage of the electrolyte and impedes the corrosion of the lithium anode. As a result, the life span of lithium-oxygen batteries is dramatically increased from 55 to 438 cycles, and the rate performance and full-discharge capacity are also massively enhanced. The battery failure is attributed to the degradation of gold nanocolloid electrolytes, and further studies on improvement of colloid stability during battery cycling are underway.

Microbial fuel cells (MFCs) that simultaneously remove organic contaminants and recovering metals provide a potential route for industry to adopt clean technologies. In this work, two goals were set: to study the feasibility of zinc removal from industrial effluents using MFCs and to understand the removal process by using reaction rate models. The removal of Zn2+ in MFC was over 96% for synthetic and industrial samples with initial Zn2+ concentrations less than 2.0 mM after 22 h of operation. However, only 83 and 42% of the zinc recovered from synthetic and industrial samples, respectively, was attached on the cathode surface of the MFCs. The results marked the domination of electroprecipitation rather than the electrodeposition process in the industrial samples. Energy dispersive X-ray (EDX) analysis showed that the recovered compound contained not only Zn but also O, evidence that Zn(OH)2 could be formed. The removal of Zn2+ in the MFC followed a mechanism where oxygen was reduced to hydroxide before reacting with Zn2+. Nernst equations and rate law expressions were derived to understand the mechanism and used to estimate the Zn2+ concentration and removal efficiency. The zero-, first- and second-order rate equations successfully fitted the data, predicted the final Zn2+ removal efficiency, and suggested that possible mechanistic reactions occurred in the electrolysis cell (direct reduction), MFC (O2 reduction), and control (chemisorption) modes. The half-life, t1/2, of the Zn2+ removal reaction using synthetic and industrial samples was estimated to be 7.0 and 2.7 h, respectively. The t1/2 values of the controls (without the power input from the MFC bioanode) were much slower and were recorded as 21.5 and 7.3 h for synthetic and industrial samples, respectively. The study suggests that MFCs can act as a sustainable and environmentally friendly technology for heavy metal removal without electrical energy input or the addition of chemicals.

The use of electrically charged, polymerized ionic liquids (polylLs) offers opportunities for the development of gel-polymer electrolytes (GPEs), but the rational design of such systems is in its infancy. In this work, we compare the properties of polyIL/IL GPEs based on 1-butyl-3-(4-vinylbenzyl)imidazolium bis(trifluromethanesulfonyl)imide containing trapped ammonium-based protic ionic liquids (ILs) with an analogous series based on the electrically neutral host polymer 1-(4-vinylbenzyl)imidazole. The materials are synthesized by photo-polymerizing ionic and neutral monomers in the presence of diethylmethylammonium trifluoromethanesulfonate, [dema] [TfO], diethylmethylammonium trifluoroacetate, [dema][TFAc], and diethylmethylammonium bis[trifluoromethanesulfonyl]imide, [dema] [Tf2N], respectively. The resulting materials are characterized using electron microscopy, infrared spectroscopy, thermal analysis, Raman spectroscopy, and AC-impedance analysis. Spectroscopic analysis confirms that the ILs are distributed throughout the polymers, unless the GPE also contains poly(diallyldimethylammonium) bis[trifluoromethanesulfonyl] imide, when separation of the components occurs. The polyIL/IL GPEs are more electrochemically and thermally stable, and up to six times more conductive, than the materials based on the neutral host. As a proof-of-concept demonstration, we show that polyIL/IL gels can be 3D printed using readily available 3D-printing hardware.

In this study, an azo dye (Acid Blue 29 or AB29) was efficiently degraded with acetate as co-substrate into less contaminated biodegraded products using an integrated single chamber microbial fuel cell (SMFC)-aerobic bioreactor set-up. The decolorization efficiencies were varied from 91 +/- 2% to 94 +/- 1.9% and more than 85% of chemical oxygen demand (COD) removal was achieved for all dye concentrations after different operating time. The highest coulombic efficiency (CE) and cell potential were 3.18 +/- 0.45% and 287.2 mV, respectively, for SMFC treating 100 mg L-1 of AB29. Electrochemical impedance spectroscopy (EIS) revealed that the anode resistance was 0.3 Omega representing an entirely grown biofilm on the anode surface resulted in higher electron transfer rate. Gas chromatography coupled mass spectrometry (GC-MS) investigation demonstrated that initially biodegradation of AB29 started with the cleavage of the azo bond (-N=N-), resulted the biotransformation into aromatic amines. In successive aerobic treatment stage, these amines were biodegraded into lower molecular weight compounds. The 16S rRNA microbial community analysis indicated that at phylum level, both inoculum and dye acclimated cultures were mainly consisting of Proteobacteria which was 27.9, 53.6 and 68.9% in inoculum, suspension and anodic biofilm, respectively. At genus level, both suspension and biofilm contained decolorization as well as electrochemically active bacteria. The outcomes exhibited that the AB29 decolorization would contest with electrogenic bacteria for electrons. (C) 2020 The Authors. Published by Elsevier B.V.

Microbial Fuel Cells (MFCs) operated as biosensors could potentially enable truly low-cost, real-time monitoring of organic loading in wastewaters. The current generated by MFCs has been correlated with conventional measures of organic load such as Biochemical Oxygen Demand (BOD), but much remains to be established in terms of the reliability and applicability of such sensors. In this study, batch-mode and multi-stage, flow-mode MFCs were operated for over 800 days and regularly re-calibrated with synthetic wastewater containing glucose and glutamic acid (GGA). BOD5 calibration curves were obtained by normalising the current measured as a percentage of maximum current. There was little drift between recalibrations and non-linear Hill models of the combined dataset had R2 of 88-95%, exhibiting a stable response over time and across devices. Nonetheless, factors which do affect calibration were also assessed. Increasing external resistance (from 43.5 to 5100 0) above the internal resistance determined by polarisation curve decreased the calibration upper limit from 240 to 30 mg/l O2 BOD5. Furthermore, more fermentable carbon sources increased the detection range, as tested with samples of real wastewater and synthetic media containing GGA, glucose-only and glutamic acid-only. Biofilm acclimatisation therefore did not account for differences between aerobic oxygen demand determinations and anaerobic MFC responses; these are likely attributable to competitive processes such as fermentation. This further highlights the potential for MFCs as real-time sensors for organic load monitoring and process control in addition to BOD-compliant measurement systems.

Formate as a medium for CO2 utilisation and energy storage.

Multi-stage microbial fuel cells can distinguish toxic shock events from BOD decreases, both of which result in decreased current output.

Ammonia will play a pivotal role in the future of zero carbon emitted sustainable fuel. The development of inexpensive efficient catalysts for ammonia electro-oxidation (AEO) is essential to its success. This study provides evidence that nanoparticles of earth-abundant elements, e.g., MoC, encapsulated in a doped-graphene shell (DG-MoC), are promising cocatalysts of Pt for AEO which significantly improve the catalyst cost and activity in comparison to the state-of-the-art platinum. DG-MoC, DG-MoC-supported Pt (Pt/DG-MoC), and nitrogen-doped-graphene (NG) catalysts were synthesized and characterized by Brunauer-Emmett- Teller (BET) surface area analysis, electrochemical techniques, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX), scanning transmission electron microscopy (STEM), and electron energy loss (EEL) spectroscopy. The XRD analysis of DG-MoC disclosed that the presence of alpha-MoC1-x, microscopy techniques demonstrates a close vicinity of Pt and MoC nanoparticles in Pt/DG-MoC. We report, for the first time, that Pt/DG-MoC particles reveal a large synergistic effect for AEO activity, while DG-MoC and NG showed no activity. Pt/DG-MoC gave a higher current density, lower half- and peak- potentials (28 mV and 14 mV, respectively), and greater resilience to ammonia poisoning than Pt/C as shown in the fall in the peak current density in the second voltammogram, i.e, approximately 3.6% compared to 20.7% for Pt/C. The XPS spectrum of the catalysts explained the source of this synergistic effect.

Diethylmethylammonium trifluoromethanesulfonate [Dema][TfO], a protic ionic liquid, was used as an electrolyte for an intermediate temperature water electrolyser. In this study we fabricated polymer electrolyte membrane based on PTFE pore filled membrane impregnated with [Dema][TfO]. The activation energy obtained for an ionic conductivity was 8.12 kJ mol(-1). Hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) were studied in the solid-state cell with an in-situ RHE reference electrode, using Pt/C cathode and IrO2 anode respectively. The HER was observed at two different potentials, one at a peak potential of -0.47 V vs RHE with a limiting current density of -9.7 mA/cm(2), assigned to reduction of hydronium ion. The second HER was observed at -0.63 V vs. RHE, assigned to the [Dema-H](+) cation reduction. Similarly, two oxidation peaks were assigned to OER one at 1.47 V and the second at 1.72 V vs RHE. The full cell water electrolyser achieved a current density of 70 mA/cm(2) at 2.2 V with 50% RH at 100 degrees C. The stability of [Dema-H](+)[TfO](-) was studied with in-situ mass spectrometry which showed the loss of DEMA at > -0.8 V vs RHE while [TfO](-) anion was stable up to 2.5 V vs RHE. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Significant reductions in total cost of ownership can be realized by engineering PEM fuel cells to run on low-purity hydrogen. One of the main drawbacks of low-purity hydrogen fuels is the carbon monoxide fraction, which poisons platinum electrocatalysts and reduces the power output below useful levels. Platinum-tungsten oxide catalyst systems have previously shown high levels of CO tolerance during both ex situ and in situ investigations. In this work, we explore the mechanism of enhanced tolerance using in situ electrochemical attenuated total reflection-infrared (ATR-IR) and Raman spectroscopy methods and investigate, using a mixture of Pt/C and WO3 powders, the role of the WV/WVI redox couple in the oxidation of adsorbed CO.

Hydrogen is a promising renewable fuel and energy storage solution, due to its highly efficient conversion with electricity and good energy density in comparison to most batteries. However, 95 % of the produced hydrogen globally is generated from non-renewable sources and only 5% is generated from electrolysis due to high systems cost [1,2]. Around 50% of the cost of the electrolyser system comes from the precious metal catalyst used in proton exchange membrane system [3,4]. Alkaline anion exchange membrane water electrolyser AAEM-WE allow the use of non-precious metals as: effective electro-catalyst and affordable flow fields and bipolar plates, reducing the cost significantly. It is estimated that replacement of PEM electrolysers with AAEM electrolysers could offer a 43% reduction in stack cost [5]. We look here at advantages and limitations of AAEM-WE and their ideal operating range. Higher performances can be achieved using high alkaline feed concentration but this in turn reduces the lifetime of the system due to degradation of AEM membrane/ionomers. Thus, in order to reduce the degradation and improve the lifetime, low alkaline concentration should be used as feed solution for AEMWE i.e. deionised water. We have shown previously [4] that an electrolyser current density of 100 mA cm-2 at 1.65V using NiCo2O4 for Oxygen Evolution Reaction (OER) could be achieved at 60 °C [4]. We present here a binary-catalyst based on manganese oxides MnOx as very efficient electro-catalyst for OER with Tafel slope of 30 mV dec-1. Using low cost LDPE based membranes radiation grafted AEM, a very promising performance electrolyser was obtained of 1.59 V at 100 mA cm-2 and a current density of 1 A cm-2 at a potential of 1.78 V in 0.01 M NaOH at 60 °C. The current highest performance reported for Ni based catalysts (2.7 mg cm-2) in the AEM system is 500 mA cm-2 at a potential of 1.9 V in 1% K2CO3 solution(pH 10-11) at 60 °C [6,7] which is ca. a third of the current density reported here. This performance is comparable to PEM electrolysers performances with the reported operating voltage is in the range of 1.6-1.7 V [8] at 1 A cm-2. However, the long-term stability of these systems remains a challenge. Keywords : AEM, water electrolysis, alkaline, non-precious metal catalyst, References: [1] Y. Cheng, S. P. Jiang, Progress in Natural Science: Materials International 2015, 25, 545-553. [2] M. N. Manage, D. Hodgson, N. Milligan, S. J. R. Simons, D. J. L. Brett, International Journal of Hydrogen Energy 2011, 36, 5782-5796. [3] S. Satyapal, C. Ainscough, D. Peterson, E. Miller, in Hydrogen Production Cost from PEM Electrolysis, DOE Hydrogen and Fuel Cells Program Record, Department of Energy, United States of America, 2014. [4] G. Gupta, K. Scott, M. Mamlouk, Journal of Power Sources 2018, 375, 387-396. [5] http://www.itm-power.com/wp-content/uploads/2012/04/CaseStudy4-ReducingCostOfHydrogenProduction.pdf [6] I. Vincent, D. Bessarabov, Renewable and Sustainable Energy Reviews 2018, 81, 1690-1704. [7] C. C. Pavel, F. Cecconi, C. Emiliani, S. Santiccioli, A. Scaffidi, S. Catanorchi, M. Comotti, Angew Chem Int Ed Engl 2014, 53, 1378-1381. [8] U. Babic, M. Suermann, F. N. Büchi, L. Gubler, T. J. Schmidt, Journal of The Electrochemical Society 2017, 164, F387-F399.

The performance of a novel electro-reformer for the production of hydrogen by electroreforming alcohols (methanol, ethanol and glycerol) without an external electrical energy input is described. This tandem cell consists of an alcohol fuel cell coupled directly to an alcohol reformer, negating the requirement for external electricity supply and thus reducing the cost of operation and installation. The tandem cell uses a polymer electrolyte membrane (PEM) based fuel cell and electrolyser. At 80 degrees C, hydrogen was generated from methanol, by the tandem PEM cell, at current densities above 200 mA cm(-2), without using an external electricity supply. At this condition the electro-reformer voltage was 0.32 V at an energy input (supplied by the fuel cell component) of 0.91 kWh/Nm(3); i.e. less than 20% of the theoretical value for hydrogen generation by water electrolysis (4.7 kWh/Nm(3)) with zero electrical energy input from any external power source. The hydrogen generation rate was 6.2 x 10(-4) mol (H-2) h(-1). The hydrogen production rate of the tandem cell with ethanol and glycerol was approximately an order of magnitude lower, than that with methanol. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.