Charge Transfer Resistance Of Cathode Research Articles

Humidity-Induced Degradation Mapping of Pt3Co ORR Catalyst for PEFC by In-Operando Electrochemistry and Ex Situ SAXS.

Understanding the degradation mechanisms of Pt-alloy catalysts is crucial for enhancing their durability. This study investigates the impact of relative humidity on Pt and Pt3Co catalysts using potential-cycling-based accelerated stress tests. Two conditions are investigated: 100% relative humidity on both sides, and a gradient with 30% at the anode and over 100% at the cathode. Pt3Co demonstrates sensitivity, with 77% performance loss and reductions in electrocatalyst surface area. Results demonstrate a 30% decrease in potential loss for Pt catalysts and a 77% increase for Pt3Co catalysts, indicating significant performance degradation in high humidity conditions, with Pt3Co exhibiting greater sensitivity. Measurements of electrochemically active surface area reinforce these findings. Resistance analysis using electrochemical impedance spectroscopy using equivalent circuit modeling reveals a threefold increase in Pt3Co MEAs' cathode charge transfer resistance and mass transport resistance during accelerated stress tests. Local current distribution analysis highlights differences between Pt catalyst and Pt3Co, with the latter displaying dealloying effects. Small-angle X-ray scattering reveals changes in particle and cluster sizes, indicating structural changes. Scanning electron microscopy highlights catalyst and membrane thickness variations, suggesting heterogeneity in Pt3Co. Under humidity gradients, Ostwald ripening plays a significant role in altering the catalyst's Pt3Co structure and subsequently impacting its performance.

Second-Harmonic Nonlinear Electrochemical Impedance Spectroscopy: Part II. Model-Based Analysis of Lithium-Ion Battery Experiments

Quantitative analysis of electrochemical impedance spectroscopy (EIS) and 2nd-harmonic nonlinear EIS (2nd-NLEIS) data from commercial Li-ion batteries is performed using the porous electrode half-cell models developed in Part I. Because EIS and 2nd-NLEIS signals have opposite parity, the full-cell EIS model relies on the sum of cathode and anode half-cells whereas the full-cell 2nd-NLEIS model requires subtraction of the anode half-cell from the cathode. The full-cell EIS model produces a low error fit to EIS measurements, but importing EIS best-fit parameters into the 2nd-NLEIS model fails to ensure robust model-data convergence. In contrast, simultaneously fitting opposite parity EIS and 2nd-NLEIS models to the corresponding magnitude-normalized experimental data provides a lower total error fit, more internally self-consistent parameters, and better assignment of parameters to individual electrodes than EIS analysis alone. Our results quantify the extent that mild aging of cells (<1% capacity loss) results in substantial increases in cathode charge transfer resistance, and for the first time, a breakdown in cathode charge transfer symmetry at 30% and lower state-of-charge (SoC). New avenues for model-based analysis are discussed for full-cell diagnostic and we identify several open questions.

State of Charge-Dependent Impedance Spectroscopy as a Helpful Tool to Identify Reasons for Fast Capacity Fading in All-Solid-State Batteries.

Thiophosphate-based all-solid-state batteries (ASSBs) are considered the most promising candidate for the next generation of energy storage systems. However, thiophosphate-based ASSBs suffer from fast capacity fading with nickel-rich cathode materials. In many reports, this capacity fading is attributed to an increase of the charge transfer resistance of the composite cathode caused by interface degradation and/or chemo-mechanical failure. The change in the charge transfer resistance is typically determined using impedance spectroscopy after charging the cells. In this work, we demonstrate that large differences in the long-term cycling performance also arise in cells, which exhibit a comparable charge transfer resistance at the cathode side. Our results confirm that the charge transfer resistance of the cathode is not necessarily responsible for capacity fading. Other processes, such as resistive processes on the anode side, can also play a major role. Since these processes usually depend on the state of charge, they may not appear in the impedance spectra of fully charged cells; i.e., analyzing the impedance spectra of charged cells alone is insufficient for the identification of major resistive processes. Thus, we recommend measuring the impedance at different potentials to get a complete understanding of the reasons for capacity fading in ASSBs.

Surface Functionalization of LiNi7.0Co0.15Mn0.15O2 with Fumed Li2ZrO3 via a Cost‐Effective Dry‐Coating Process for Enhanced Performance in Solid‐State Batteries

AbstractApplying a thin film coating is a vital strategy to enhance long term and interface stability of Ni‐rich layered oxide cathode materials (NRLOs), especially when they are matched with sulfidic solid electrolytes (SSEs) in solid‐state batteries (SSBs). The coating prevents direct contact between the cathode active material (CAM) and the SSE, shielding against parasitic side reactions at the cathode electrolyte interface (CEI). Conventional coatings are based on wet‐chemical methods and therefore harmful to the environment and require long‐lasting processing and high costs. In this study, we present a versatile, facile and highly‐scalable dry‐coating method (with suitable equipment up to 500 kg per batch) successfully employed for both multi‐ and single‐crystalline LiNi0.70Mn0.15Co0.15O2 (NCM70) particles by fumed Li2ZrO3 nanostructured particles (LZONPs) via high intensity mixing process. The resulting porous coating layer stays firmly attached at the CAM particle surface without a need of post‐calcination step at elevated temperatures. The electrochemical testing results signify enhanced rate capability up to 1.5 mA cm−2 for both particle types and cyclic stability up to 650 cycles with a capacity retention of 86.1 % for single‐crystalline NCM70. We attribute the enhanced performance to the reduced CEI reactions as cathodic charge transfer resistance depressed significantly after dry‐coating by LZONPs, being an important step towards sulfidic solid‐state batteries.

Controlling hydrophilic channel alignment of perfluorinated sulfonic acid membranes via biaxial drawing for high performance and durable polymer electrolyte membrane water electrolysis

This study focuses on improving performance and durability of perfluorinated sulfonic acid (PFSA) membranes for polymer electrolyte membrane water electrolysis by controlling the membrane microstructure. To replace the highly gas permeable and expensive PFSA membranes, a membrane with low gas permeability and ohmic resistance is required for the high performing and safe water electrolyzers. Here, a thick PFSA membrane, Nafion 117 is biaxially stretched up to 6.4 times to reduce the membrane thickness, and increase the hydrophilic channels’ tortuosity. The thinned and planarly stretched Nafion shows better cell performance and durability at a constant current than the thick Nafion due to the reduced ohmic resistance and the enhanced interfacial stability between membrane and catalyst layer. With more tortuous hydrophilic pathways of the stretched Nafion, hydrogen permeability is reduced by a factor of 1.6, which is beneficial to prevent the membrane degradation and also to widen the operating current density range. The current density at 1.9 V increases from 1.5 to 3.2 A/cm 2 after stretching, and the biaxially stretched membrane shows 4 times lower enhancement in ohmic and cathodic charge transfer resistance than the similarly thick Nafion after the constant current experiment, yielding 2.5 times lower degradation rate. • Nafion 117 was biaxially stretched for PEMWE. • Planarly oriented hydrophilic channels reduced the hydrogen permeation. • Biaxially stretched Nafion showed higher cell performance. • Interfacial stability with the stretched Nafion was better than the un-stretched one.

CuO/g-C3N4 heterojunction photocathode enhances the microbial electrosynthesis of acetate through CO2 reduction

Microbial electrosynthesis (MES) is a novel CO2 utilization technology. Biocatalysts in this process may use electrons obtained from a photovoltaic system to reduce CO2 to chemicals and realize energy conversion from solar energy to chemical energy. The photoelectric material CuO/g-C3N4 was directly introduced into the MES system using mixed culture as biocatalyst in this study. CuO/g-C3N4 can effectively absorb light and presents satisfactory electron and hole separation ability. Photogenerated electrons from CuO/g-C3N4 enhanced the electron transfer rate and reduced cathodic charge transfer resistance. CuO/g-C3N4 mainly improved the electron supply of electroautotrophic microorganisms through direct electron transfer rather than indirect electron transfer via hydrogen. Photogenerated holes can combine electrons from anode and provide extra driving force to improve the MES performance. Furthermore, the CuO/g-C3N4 photocathode also improved the biocatalytic activity by increasing the total amount of biocatalyst and regulating cathodic microbial community composition. Acetate production rate in MES with the CuO/g-C3N4 photocathode was 2.6 times higher than that of the control group. This study provides a new strategy for semiconductor photocathodes to improve the MES performance with mixed culture.

Catalyst layers for fluorine‐free hydrocarbon PEMFCs

Herein, we study catalyst ink composition on the current-voltage characteristics of fuel cells incorporating fully hydrocarbon-based membrane-electrode-assemblies. The membrane and ionomer used for these studies is sulfo-phenylated poly(phenylene) biphenyl (sPPB-H+). Fuel cell current-voltage characteristics vary depending on the nature of the dispersing medium of the ink with single-cell power densities increasing for inks prepared from MeOH > EtOH > iPrOH, based on 3:1 alcohol:water mixtures. This correlates with the catalyst layer's higher BET- surface area, porosity, electrochemically active surface area (ECSA), and lower cathodic charge transfer resistance. Despite this, MeOH-based catalyst inks yield catalyst layers with relatively high ionic resistance, which is postulated to result from the poor integrity of ionomer films coating C/Pt aggregates within the catalyst layer. This deficiency is mitigated using low surface area Vulcan XC-72 catalyst support. Using low surface area carbon supports, a satisfactory proton conduction network can be established in the catalyst layer with ionomer contents as low as 2.5 wt% (∼0.023 mgionomer cm-2), with a > 10% increase in peak power density (H2/Air) compared to a conventional D520-Nafion®-based MEA containing 30 wt% ionomer in the catalyst layer (∼ 0.28 mg cm-2).

Investigation of Simultaneous Influences of Significant Charging Factors on Lithium‐Ion Batteries and Identifying Interaction Effects

Lithium‐ion batteries are an essential technology with extensive use in numerous electric applications. A complete understanding of the simultaneous effects of charging factors such as state‐of‐charge (SOC), C‐rate, and rest period is essential to manage lithium‐ion batteries. This study aims to determine the significant charging factors influencing the battery dynamics to provide detailed insights into the relationship between the selected charging factors and the battery dynamics. The cathodic charge transfer resistance and the ohmic resistance are substantially affected by the C‐rate, whereas the SOC dominantly contributes to only the Rt;c. The effect of the SOC on the ohmic resistance and the cathodic charge transfer resistance depends on the C‐rate. The cathode charge transfer resistance is the most sensitive dynamic parameter to charging factors. The solid electrolyte interphase formation charge transfer resistance is the most stable battery dynamic parameter. The sensitivity analysis expressly shows the part of the lithium‐ion battery that needs to be improved to provide better performance under the implemented charging protocols. Comprehensive analysis of the simultaneous effects of charging factors on battery dynamics can also be used in a battery management system to measure changes in battery dynamics that will support lithium‐ion battery controls.

Influence of charge conditions on battery dynamics of a commercial lithium-ion cell

Electrochemical impedance spectroscopy measurements were performed to determine the effect of the state-of-charge, charge current, and current-drop time on battery dynamics of a commercial 2032 lithium-ion coin cell. The impedance response was systematically investigated and discussed by using the Taguchi design. The results showed that the state-of-charge had a statistically significant effect on both the resistance for solid electrolyte interphase formation and cathodic charge transfer resistance. It was showed that the Taguchi design is a valuable tool for analyzing battery dynamics obtained through the equivalent circuit model. The Taguchi design opened the door for a robust design of lithium-ion batteries in real life.

Electricity generation from paddy soil for powering an electronic timer and an analysis of active exoelectrogenic bacteria

In farmlands, most electronic devices have no connection to a power source and have to work on batteries. To explore paddy soil as an in situ power source, herein, we in the present study constructed sediment microbial fuel cells (SMFCs) in paddy soil. An open circuit voltage of 1.596 V and a maximum power density of 29.42 mWm−2 were obtained by serially connecting three SMFCs. Electrochemical impedance spectroscopy showed that the internal resistance which comprised ohmic resistance and anodic and cathodic charge transfer resistance was approximately 400 Ω for each of the three individual SMFCs. We used the serially connected SMFCs to power an electronic timer through a 1 F capacitor. The SMFCs had powered the timer for 80 h until the potential of the SMFCs dropped below 0.936 V. Then, RNA was extracted from anode samples and 16S rRNA was sequenced following reverse transcription. The results showed that the relative abundance of active exoelectrogenic bacteria-associated genera on the anode was 13.03%, 27.78%, and 16.17% for the three SMFCs with Geobacter and Anaeromyxobacter being the dominant genera. Our findings provide the possibility of powering electronic devices in the field by using soil as a power source.

Enhancing the performance of photo-bioelectrochemical fuel cell using graphene oxide/cobalt/polypyrrole composite modified photo-biocathode in the presence of antibiotic

Photo-bioelectrochemical fuel cell (PBFC) holds a great potential to harvest sustainable electrical energy from wastewater, but low power output limits its applications due to poor electrochemical performance of photo-biocathode. Additionally, antibiotics are ubiquitous in wastewater streams, but little is known regarding their effects on photo-biocathode performance of the PBFC. This study attempted to increase power output of PBFC through improvement of the photo-biocathode performance by modifying the biocathode with graphene oxide/cobalt/polypyrrole (GO/Co/PPy) composite in the presence of oxytetracycline. The GO/Co/PPy composite modified electrode fabricated by one-step electropolymerization method exhibited more excellent catalytic activity toward oxygen reduction compared to Co-alone and Co/PPy modified electrode. The PBFC with GO/Co/PPy composite modified biocathode produced a maximum power density of 19 mW/m2, which was almost 4-fold higher than that produced with the bare biocathode (4.9 mW/m2) due to improved bio-electrocatalytic performance of the bicathode by the GO/Co/PPy composite. The maximum power density of the PBFC was further increased 4.6 (105.5 mW/m2), 3.7 (88.7 mW/m2), 2.9 (74.6 mW/m2) and 1.9 (56 mW/m2) fold by exposure to 5, 10, 20, and 50 mg/L OTC, respectively. The further increases in power was due to reduced cathode's charge transfer resistance using degradation products of OTC as mediators and OTC-stimulated growth of species with extracellular electron transfer ability. However, the photosynthesis and growth of alga was negatively affected by OTC concentration higher than 10 mg/L, resulting performance deterioration of bicathode.

A Novel Sediment Microbial Fuel Cell Based Sensor for On‐Line and in situ Monitoring Copper Shock in Water

AbstractTo online and in situ monitor the heavy metal shock in water, a novel sediment microbial fuel cell based sensor was developed with anode being inserted into flooded soil and cathode submerged in overlaying water. Immediately after CuSO4 solutions were added into the overlaying water, the voltage signal generated by the sensor reached a peak and the increment from baseline voltage to peak voltage increased linearly with Cu2+ concentrations up to 160 mg L−1. After Cu2+ shock, charge transfer resistance (Rct) of anode and cathode was determined by using electrochemical impedance spectroscopy. Soil DNA and RNA was extracted and 16S rRNA and 16S rRNA gene of dominant exoelectrogenic bacteria (Geobacter and Clostridium) was quantified. Result showed that Cu2+ shock decreased cathodic charge transfer resistance (Rct) but did not affect anodic Rct. The addition of 320 mg L−1 Cu2+ significantly reduced abundance and activity of Geobacter and Clostridium in surface soil (0–3 cm in depth) but had no effect on exoelectrogenic bacteria in deeper soil. Moreover, baseline voltage was stable after Cu2+ shock. The result indicates that the sensor could online and in situ monitor Cu2+ shock which increased voltage signal by promoting cathodic reaction without dramatically inhibiting exoelectrogenic bacteria.

Catalyst degradation diagnostics of proton exchange membrane fuel cells using electrochemical impedance spectroscopy

A previously validated equivalent circuit model, in which two resonant circuits were inserted to represent the processes in the catalyst layers, is applied to fit the electrochemical impedance spectroscopy results of a single proton exchange membrane fuel cell exposed to accelerated stress test targeting catalyst degradation. The simulation results of the applied equivalent circuit model show very good agreement with the experimental data. The applied model is able to extract contributions of each of the model elements to the cell degradation. The obtained results indicate that the cathode catalyst layer resonant loop parameters, together with the cathode charge transfer resistance and cathode double-layer capacitance, change the most during the accelerated stress test. If each of the elements of the cathode resonant loop can be associated with physical processes inside the catalyst layer, the model may be used to give more insight into the degradation effects on functioning of the catalyst layer. From the conducted electrochemical impedance spectroscopy analysis, it seems that the low-frequency intercept in Nyquist plot shows the most significant change with degradation, so it may be used directly as a sufficient indicator of fuel cell performance degradation due to catalyst layer degradation.

Lithium ion batteries (NMC/graphite) cycling at 80 °C: Different electrolytes and related degradation mechanism

A comprehensive study on high temperature cycling (80 °C) of industrial manufactured Li-ion pouch cells (NMC-111/Graphite) filled with different electrolytes is introduced. Ageing processes such as capacity fade, resistance increase and gas generation are reduced by the choice of appropriate electrolyte formulations. However, even by using additive formulations designed for elevated temperatures a large resistance increase is observed after 200 cycles and more (which does not happen at 55 °C). Symmetrical EIS (Electrochemical Impedance Spectroscopy) shows that the cathodic charge transfer resistance is the main reason for this behaviour. Nonetheless most of the active Li is still available when cycling with suitable additives. No change of the cathode crystalline structure or a growth of the cathodic surface reconstruction layer is observed post cycling at 80 °C. Therefore a disintegration of NMC secondary particles is believed to be the main reason of the cell failure. A separation of single grains is leading to new decomposition and reconstruction layers between primary particles and an increased charge transfer resistance. Further approaches to improve the high temperature cycle stability of NMC based materials should therefore be aimed at the cathode particles morphology in combination with similar electrolyte formulations as used in this study.

(Invited) Experimental and Physically Based Modelling Analysis of Electrochemical Impedance in PEMFC to Interpret Performance Degradation Causes

The required target for mass deployment of PEMFC in different applications is still not fully achieved, because of a severe performance decay, determined by the interaction of several degradation mechanisms [1]. The comprehension of such mechanisms and the influence of operating condition stressors is still not satisfactory to accurately predict fuel cell lifetime during real operation. Especially the components structural and functional alteration in time, observed by ex-situ techniques, can be hardly associated to a distinct contribution to performance loss. Electrochemical impedance spectroscopy is a promising in-situ technique to distinguish the contributions of different degradation phenomena, but nowadays data analysis is widely performed modelling the fuel cell through simplified electrical circuits that do not permit to achieve a solid physical interpretation of performance degradation causes. A physically based modelling approach, recently explored in the literature [2,3], can cover this gap, however it is not fully consolidated yet and the required effort to develop appropriate tools limits today its utilization to modelling experts. The present work aims at presenting the effectiveness of an approach that combines experimental and physically based modelling analysis of electrochemical impedance in investigating performance degradation occurring in different technologies [4-7]: HT-PEMFC, Low-Pt PEMFC, DMFC, PGM-free PEMFC. The general methodology is presented, highlighting the possible onset of different regimes, where distinct phenomena prevail. The continuum model based on macro-homogenous assumption, solves mass and ionic conservation coupled with Stefan-Maxwell diffusion and Ohm’s law; electrochemical reactions are described with Butler-Volmer kinetics. EIS is solved according to the approach reported in [5]. Subsequently some relevant cases are discussed in details, emphasizing the influence of heterogeneous degradation [5] and local mass transport [7]. One analysis reported in this work is the effect of heterogeneity of ageing on EIS, which determine an increase of the cathodic charge transfer resistance that is not ascribed to a loss of electrochemical active surface, but to the uneven distribution of the reaction rate. Another analysis reported in this work consists in the simulation of EIS with commercial CFD codes: the effect of 3D geometrical features was analyzed, e.g bends in the flow field, flow bypass between channels, interdigitated flow pattern. [1] Boroup, R., & al. (2007). Scientific aspects of Polymer Electrolyte Fuel Cell durability and degradation. Chemical Reviews, 107, 3904-3951. [2] Baricci, A., Zago, M., & Casalegno, A. (2014). A quasi 2D model of a High Temperature Polymer Fuel Cell for the interpretation of impedance spectra. Fuel Cells, 14, 926-937. [3] Kulikovsky, A.A., (2012). A physical model for catalyst layer impedance. Journal of Electroanalytical Chemistry, 669, 28-34 [4] Bresciani, F., Casalegno, a., Zago, M., & Marchesi, R. (2013). A parametric analysis on DMFC anode degradation. Fuel Cells, 14, 386–394. [5] Baricci, A., Zago, M., & Casalegno, A. (2016). Modelling analysis of heterogeneity of ageing in high temperature polymer electrolyte fuel cells: insight into the evolution of electrochemical impedance spectra. Electrochimica Acta, 222, 596–607. [6] Casalegno, A., Baricci, A., Bisello, A., Odgaard, M., Serov, A., & Atanassov, P. (2017). Insight into degradation mechanism in non-precious metal composite catalysts for PEMFC. 7th FDFC, Stuttgart. [7] Baricci, A., Mereu, R., Messaggi, M., Zago, M., Inzoli, F., & Casalegno, A. (2017). Modeling analysis of flow field geometrical features in Polymer Electrolyte Fuel Cells porous media. 7th FDFC, Stuttgart.

A comprehensive study on development of a biocathode for cleaner production of hydrogen in a microbial electrolysis cell

A biocathode microbial electrolysis cell (MEC) can be considered as an environmentally friendly and self-generative alternative to an abiocathode MEC for the cleaner production of hydrogen in a novel microbial electrolysis system. For the first time, this research focused on the development of the MEC biocathode out of sulphate-reducing bacteria (SRB) for the purpose of hydrogen production based on the previously proposed hypothesis. SRB were initially enriched from a mixed culture source during the ex-situ SRB enrichment stage. Two different MEC bioathodes- namely, the MEC origin (MEC-O) biocathode and the microbial fuel cell-MEC (MFC-MEC) biocathode- were then developed through two different enrichment procedures during the in-situ SRB enrichment stage. Hydrogen gas was the main product of the MEC-O biocathode with a low detection of methane, while methane was detected as the sole product of the MFC-MEC biocathode system. Therefore, the MEC-O biocathode system was selected during the enhancement stage to increase the biocathode MEC performance. It was shown in the study, that in the enhancement stage of the MEC-O biocathode, the concentration of sodium sulphate in the cathodic medium, the hydrogen supply during the enrichment stage and pH of the cathodic medium could significantly affect the MEC performance in terms of the hydrogen production rate, the onset potential for the hydrogen evolution reaction (HER) and the cathodic charge transfer resistance. The hydrogen production was improved significantly by about 6 times from 0.31 to 1.85 m3 H2/(m3 d) during the enhancement stage, while the methane production was totally hindered. The linear sweep voltammetry analysis displayed a 430-mV (equal to about 1 kWh/m3 of energy input) reduction of the HER onset potential in the biocathode system compared to that of a non-inoculated graphite felt cathode. Moreover, the electrochemical impedance spectroscopy showed that the cathodic charge transfer resistance of the MEC biocathode reduced by 300 times compared to that of a non-inoculated graphite felt cathode.

The effect of flow-field structure in toluene hydrogenation electrolyzer for energy carrier synthesis system

In this study, we investigated the effect of the design of the cathode flow-field structure on the electrochemical performance of the electrolyzer for the toluene-methylcyclohexane electrocatalytic hydrogenation synthesis system. The patterns of the basic flow-fields; i.e. parallel, interdigit, serpentine and porous-carbon, were investigated based on linear sweep voltammetry (LSV), internal, and cathodic and anodic charge transfer resistances with impedance spectroscopy and current efficiency. The flow-field pattern affected the toluene mass transportation and H2 gas generation as a side reaction. Based on the LSV curve, the porous-carbon did not affect the overvoltage for the decrease in the toluene concentration, and showed the lowest cell voltage in the all flow-fields. The cathodic charge transfer resistance by impedance analysis and the current efficiency of the porous-carbon showed the highest performance in the all flow-fields over a wide toluene concentration range.

Carbon supported Ni1Pt1 nanocatalyst as superior electrocatalyst with increased power density in direct borohydride-hydrogen peroxide and investigation of cell impedance at different temperatures and discharging currents

Carbon supported NiPt and Pt nanoparticles are synthesized using chemical reduction with sodium borohydride (NaBH4). The metal loading in synthesized nanocatalysts was 20 wt% and the ratio of Ni:Pt in the nanocatalysts was 1:1. The physical properties of nanocatalysts are investigated by Field Emission scanning electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of the NiPt/C and Pt/C catalysts toward BH4− oxidation in alkaline media is investigated by means of cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA). The current densities are normalized respect to actual Pt loading in the nanocatalysts. Cyclic voltammograms show that the NiPt/C electrocatalyst has higher catalytic activity toward NaBH4 electrooxidation. A direct borohydride-hydrogen peroxide fuel cell (DBHPFC) is fabricated using Pt/C (0.5 mg cm−2) as cathodic catalyst and NiPt/C (1 mg cm−2) as anodic catalyst. The influence of cell temperature, sodium borohydride and hydrogen peroxide concentration on the I-V and I-P curves is investigated. The obtained maximum power density is 106.63 mW cm−2 at 60 °C, 1 M NaBH4 and 2 M H2O2. Impedance spectrums are taken in NaBH4 1 M + H2O2 2 M. The impedance results show that with increasing temperature and discharging current, anodic and cathodic charge transfer resistance reduce.

Simultaneous Wastewater Treatment, Algal Biomass Production and Electricity Generation in Clayware Microbial Carbon Capture Cells.

Performance of microbial carbon capture cells (MCCs), having a low-cost clayware separator, was evaluated in terms of wastewater treatment and electricity generation using algae Chlorella pyrenoidosa in MCC-1 and Anabaena ambigua in MCC-2 and without algae in a cathodic chamber of MCC-3. Higher power production was achieved in MCC-1 (6.4W/m3) compared to MCC-2 (4.29W/m3) and MCC-3 (3.29W/m3). Higher coulombic efficiency (15.23±1.30%) and biomass production (66.4±4.7mg/(L*day)) in MCC-1 indicated the superiority of Chlorella over Anabaena algae for carbon capture and oxygen production to facilitate the cathodic reduction. Algal biofilm formation on the cathode surface of MCC-1 increased dissolved oxygen in the catholyte and decreased the cathodic charge transfer resistance with increase in reduction current. Electrochemical analyses revealed slow cathodic reactions and increase in internal resistance in MCC-2 (55 Ω) than MCC-1 (30 Ω), due to lower oxygen produced by Anabaena algae. Thus, biomass production in conjunction with wastewater treatment, CO2 sequestration and electricity generation can be achieved using Chlorella algal biocathode in MCC.

Design of High Performance Intermediate Temperature Fuel Cells Based on BaCe0.8Y0.2O3/Pd Heterointerfaces

The current PCFC performance lags far behind the SOFC performance even at the intermediate temperature (IT) range of 400-600°C, even though proton-conducting perovskite type oxides, such as BaCe0.8M0.2O3 (M=Y, Gd, Yb etc.) exhibit higher ion conductivity than the oxide ion conducting oxides used as an electrolyte of SOFCs. One of major reasons for the deteriorated performance is large cathodic interfacial polarization due to a lack of suitable cathode for PCFC operation. Meanwhile, exceptionally high power output has been reported for a hydrogen membrane fuel cell (HMFC) in the temperature range of 400-600°C, which consists of a thin proton conducting ceramic electrolyte supported on a dense hydrogen permeable metal anode. Hence, it is of fundamental and of technological interest to investigate the cathode and anode interfacial polarization of HMFC in order to clarify the mechanism for the high efficiency power generation. In the present study, we successfully fabricated high efficiency hydrogen membrane fuel cells based on BaCe0.8Y0.2O3- d thin film with hydrogen permeable Pd solid anode and conventional La0.6Sr0.4Co0.2Fe0.8O3 cathode. BaCe0.8Y0.2O3- d (BCY) thin films were fabricated by RF sputtering with a single BaCe0.8Y0.2O3- d target or cosputtering with BaCe0.8Y0.2O3- d and Ce0.8Y0.2O2 double targets. The sputtering conditions of sputtering power, process atmosphere, target-substrate distance, substrate temperature and post-annealing temperature were optimized to prepare a highly crystalline film having the same composition as the target composition. The hydrogen membrane fuel cells were fabricated by depositing a BCY thin film of 1 mm thickness on a hydrogen-permeable Pd anode by RF sputtering in optimal condition. The Pd foil (0.05 mm thickness, Tanaka Co.) was used as a solid anode. The foil (12 ´ 12) was polished with alumina particles (1.0 μm diameter) and was cleaned by sonication in acetone and pure water before deposition. La0.6Sr0.4Fe0.8Co0.2O3 (LSCF) button electrode (5 mmÆ) was deposited on the BCY films as a porous cathode by screen-printing with a commercial LSCF paste (NexTech) and subsequent heating with heat-gun for 2 min. The performance of BCY thin film base HMFC was evaluated by measuring the current-voltage (I-V) relation and electrochemical impedance spectra. I-V and I-P characteristics of HMFC consisting of 1 mm thick BCY thin film were measured at 520, 550, 570 and 600°C (Fig. 1). The performance is drastically improved at higher temperature; the cell can gives maximum power density of 1050 mW cm-2 and OCV of 1.08 V at 600°C. This value is higher than the champion data of the maximum power density of PCFCs [1]. The power output is very stable and the current keeps about 1300 mA cm-2 at 0.7 V for a few hours. The impedance spectra of HMFC were replicated with an equivalent circuit build by series connection of cathode charge transfer elements and anode mass transfer elements. The contribution of the mass transfer in Pd bulk was found to be relatively small in comparison to cathode polarization and ohmic loss in normal fuel cell atmosphere. Moreover, the cathodic charge transfer resistance of HMFC was found to be smaller than those of the recent PCFC systems by 25 times. The current results demonstrated that the HMFC retained relatively large gas-proton-electron triple boundary zones near interface between BaCe0.8Y0.2O3- d electrolyte and porous La0.6Sr0.4Co0.2Fe0.8O3- d cathode. The I-V characteristics of the HMFC was measured by supplying wet Ar to LSCF side and dry Ar to Pd side, exhibiting rectification, where negative bias on Pd is the reverse bias. These indicate that BCY/Pd heterointerface works as a Schottky junction of n-type BCY and large work function Pd metal. [1] Kim, J.; Sengodan, S.; Kwon, G.; Ding, D.; Shin, J.; Liu, M.; Kim, G. ChemSusChem 2014, 7, 2811.