Fuel Cell System Research Articles

Renewable fuel-powered micro-gas turbine and hydrogen fuel cell systems: Exploring scenarios of technology, control, and operation

Two technology options, a proton exchange membrane (PEM) fuel cell and a recuperated micro-gas turbine (MGT) consisting of equipment with variable efficiencies and a controllable bypass valve, are modeled numerically. The validated simulations are studied under multiple scenarios, including technology, control, and operation. Under the technology scenario, the PEM fuel cell depicts higher net heat energy (1390.5 kW) with an overall efficiency of 93.27 %, significantly reducing thermal dissipation compared to the MGT, which has a low heat-to-power ratio (0.69) with the same hydrogen combustion rate (0.018 kg s−1). Following the fuel scenario, at 40 %-part load and 100 % bypass valve position, the highest net power (137.08 kW) and heat generation (635.07 kW) are achieved when 0.009 kg s−1 of hydrogen is combusted in MGT, exceeding other fuel utilization. In addition, the heating control strategy determines the availability status of the proposed technologies. The observed operational trends indicate effective fulfillment of urban heating needs by hydrogen combustion during Winter and Fall. However, the utilization of biogas leads to significant functional limitations. Finally, the operating function of the PEM fuel cell under off-design conditions is evaluated, resulting in notable enhancements in energy outputs and hydrogen consumption when considering the combination of control parameters compared to their individual evaluations.

Technical, economic and environmental assessment and optimization of four hybrid renewable energy models for rural electrification

This work investigates the technical, economic and environmental feasibility of four solar – wind off grid hybrid renewable energy system (HRES) models to provide electrification for Okorobo-Ile town in Andoni Local Government Area of River State, Nigeria using the Hybrid Optimization of Multiple Electric Renewables (HOMER) software. In particular, investigation of the possible inclusion of a fuel cell (FC) system is performed. The four considered models are: pv/wind/battery (PWB); pv/wind/battery/gen-set (PWBG), pv/wind/fuel-cell (PWF) and pv/wind/battery/fuel-cell (PWBF). The best cost-effective configuration among the set of systems were examined for the electricity requirement of 677.75 kWh/day primary load with 99.1 kW peak load. Results obtained showed that the net present cost (NPC) are $615,664.95, $679,348.17, $778,834.22 and $3,534,850.54 respectively for the PWB, PWBG, PWBF and PWF. The cost of energy (COE) was lowest for the PWB with a value of $$0.158 and highest for the PWF with a value of $0.964. The renewable options—PWBF and PWF have higher long-term costs but offer cleaner emissions. In contrast, options with the Diesel-Powered Generator is cost-effective but has a high environmental impact in terms of greenhouse gas emissions and noise pollution. These emissions include 3,758 kg/yr CO2, 23.7 kg/yr CO and a total of 32.67 kg/yr of unburned hydrocarbons, sulfur dioxide, particulate matter and nitrogen oxides. Based on the results, a stand - alone HRES that consist of 166 kW PV panels, 3 wind turbines 29 batteries and 123 kW converter is found to be the best configuration for the village, as it leads to minimum net present cost (NPC) and COE. The PWB system offers the best choice for the community by balancing financial considerations with sustainability which is crucial when making energy system choices. Results also show that while hydrogen, FC system and the electrolyzer can be used together with or without batteries, inclusion of the FC system resulted in the high NPC due to their high cost of investment.

A High-Speed, High-Temperature, Micro-Cantilever Steam Turbine for Hot Syngas Compression in Small-Scale Combined Heat and Power

Abstract Coupling a biomass gasifier with a solid oxide fuel cell system through a high-temperature syngas compressor holds great promise to achieve low-emission, small-scale combined heat and power, since it reduces the number of heat exchangers and increases the system efficiency. However, due to the demanding operating conditions (high temperatures, toxic and explosive gases), electrical motors are not suitable to drive the syngas compressor. Therefore, a high-speed, small-scale cantilever steam turbine that can valorize the system?s waste heat to power the compression is designed and developed. An iterative process involving preliminary design, meanline analysis, commercial tools, and in-house codes is used for the design. The design is then numerically analyzed using computational fluid dynamics. The 2.8 kW cantilever steam turbine with a tip diameter of 21 mm runs up to 210 krpm at temperatures of 525°C while being supported on dynamic steam-lubricated bearings. A low-reaction, full-admission design has been chosen to lower the steam consumption, the axial forces, and the turbine backface leakage. The turbine rotor is made of Ti6Al4V and coated for structural integrity and to withstand high temperatures. Despite the small scale of this design, the results obtained from the established correlations based on large-scale turbines yield a remarkable concordance with the results from the numerical analysis, in particular for the isentropic expansion efficiency prediction.

A High-Temperature, High-Speed, Oil-Free Syngas Compressor for Small-Scale Combined Heat and Power

Abstract For low-emission, small-scale combined heat and power generation, integrating a biomass gasifier with a downstream solid oxide fuel cell system is very promising due to their similar operating conditions in terms of temperatures and pressures. This match avoids intermediate high-temperature heat exchangers and improves system efficiency. However, to couple both systems, a high-temperature and oil-free compressor is required to compress and push the low-density, high-temperature bio-syngas from the gasifier to the solid oxide fuel cell stack. The design and development of this high-temperature, high-speed, and gas-bearing supported compressor is presented in this work. An iterative process involving preliminary design, meanline analysis using commercial tools and in-house models is used for the design, which is then numerically analyzed using computational fluid dynamics. The goal is to achieve a design with a wide operating range and high robustness that withstands extreme working conditions. The 727 W machine is designed to run up to 210 krpm to compress 18.23kg/h of syngas at 350°C and 0.81bar. The centrifugal compressor has a tip diameter of 38 mm and consists of 9 backswept main and splitter blades. The impeller is made of Ti6Al4V and coated to prevent hydrogen embrittlement from the hot and highly reactive bio-syngas. The results obtained from the established models suggest a good concordance with the results from numerical analyses, despite the high temperatures and small scale of this design.

Optimal power management for hybrid electrical vehicle

This paper introduces an innovative optimal energy management strategy tailored for a hybrid electric-powered hydraulic excavator system. The aim is to bolster power performance, extend the lifespan of power sources, and optimize hydrogen usage. In this system, the fuel cell serves as the primary power source, while integrating supercapacitors and batteries offers benefits such as enhancing power performance and storing regenerative energy for future use. To efficiently distribute power among these three sources and maximize the utilization of regenerative energy, we propose an energy management strategy. This strategy combines fuzzy logic control with a rule-based algorithm. Moreover, we optimize the parameters of the fuzzy logic system using a combination of the backtracking search algorithm and sequential dynamic programming. This optimization aims to reduce hydrogen consumption and prolong the lifespan of the power sources. Simulation results demonstrate that our proposed energy management strategy significantly enhances vehicle performance, improves fuel economy of the hybrid electric-powered hydraulic excavator system, and enhances the durability and efficiency of the battery and supercapacitor systems within the fuel cell system.

Optimizing power output in direct formic acid fuel cells using palladium film mediation: experimental and DFT studies

Low-temperature hydrogen production from environmentally friendly liquid fuels such as methanol, ethanol, and formic acid for miniature fuel cells used in powering portable electronic devices is attracting reasonable attention. In this study, we present the findings from the decomposition of formic acid and subsequent power generation within a microfluid fuel cell. The fuel cell system was engineered to incorporate a palladium membrane at the anode and a modified carbon Torray paper at the cathode. To assess fuel cell performance, we employed chronopotentiometry and cyclic voltammetric electro­chemical techniques. This simple fuel cell could achieve a current peak of 3.17 µW by utilizing 2.50 M HCOOH solution and 2.26 µW with 0.1 M solution, all at room temperature. Finally, to provide a deeper understanding of the reactivity and HCOOH decomposition pathways on various palladium surfaces, we conducted density functional theory (DFT) studies. Our DFT investigations revealed that the Pd(111) surface exhibited more negative adsorption energy compared to other surfaces, suggesting its propensity for a more isomeric crystal morphology. This research underscores the promising potential of low-temperature hydrogen production using safe liquid fuels in microfuel cell applications for portable electronic devices.

Experimental assessment of a heavy-duty fuel cell system in relevant operating conditions

During the past few years, the research interest in fuel cell systems (FCS) has increased significantly. Thus, this kind of powertrain is now at high Technology Readiness Levels (TRLs) and even starting to be commercialized. However, the currently available technology still has room for optimization. The existing bibliography shows studies mainly related to stack-level characterization or FCS studies with a poor level of detail. The present paper focuses on producing a detailed database about the performance of a specific FCS designed for heavy-duty vehicle (HDV) applications. The obtained dataset provides information about the influence of ambient conditions on the performance of the system, plus information about the anode and cathode circuits. These factors represent an important novelty with respect to other pieces of literature present in the actual research framework. Additionally, the obtained data regarding the performance of an FCS is highly significant for HDV manufacturers in the transportation sector and eases the pathway to the optimization of these technologies. The written piece of research proves the importance of studying the ambient conditions. The experimental campaign has shown that increasing relative humidity can improve the performance of the membrane up to a 2% for a 25% change in the humidity level. Additionally, the study shows the importance of implementing an appropriate supply gas strategy, both for anode and cathode, and designing the right purging mechanisms for H2 at the anode inlet. The obtained results show how there exist a relation between the optimal efficiency operating point and a H2 excess from the supply strategy.

An enhanced salp swarm algorithm with chaotic mapping and dynamic learning for optimizing purge process of proton exchange membrane fuel cell systems

Swarm intelligence algorithm is now a research focus for the energy optimization of fuel cell systems to improve hydrogen utilization efficiency. However, conventional algorithms exhibit poor robustness and low execution efficiency since complex constraints are involved in the fuel cell cathode purge process. Given that, this paper innovatively introduces chaotic mapping and dynamic learning mechanisms into the Salp swarm algorithm to enhance the algorithm's global search and local exploitation capabilities under complex constraints. First, we developed a three-stage nonlinear cathode purge model to describe the different water transfer behaviors in the three purging stages. Then, an optimizing function is created under the complex staged constraints to accurately reveal the energy consumption mechanism. Finally, the enhanced Salp swarm algorithm enables the rapid and accurate determination of the three-stage dynamic purge flows based on minimizing energy consumption. Compared with the fixed flow purge scheme, we found that energy consumption is reduced by 3.6 %–8.2 % under various constraints. The enhanced Salp swarm algorithm proposed in this work demonstrates an outstanding performance in the energy consumption optimization of fuel cell systems.

A novel fuel cell cathode hybrid intake structure design and control for integrated hydrogen energy utilization system

The typical Integrated Hydrogen Energy Utilization System (IHEUS) does not recycle oxygen. For maximizing the system's efficiency, this study proposes a method for recycling byproduct oxygen in a Fuel Cell (FC) hybrid cathode intake structure and its control. By introducing the pure oxygen produced as a byproduct of hydrogen production into the FC, a hybrid cathode intake structure is formed with the air branch. To control this structure, models of the oxygen and air branch, and the FC stack are established. Subsequently, using BiLSTM network to learn historical data and extract relevant features, the output power demand of the FC system is predicted. Based on the prediction results, the required gas flow is calculated, and a fuzzy PID control strategy is employed to adjust the opening of the solenoid valve to change the gas flow to meet the demand. Finally, comparative studies show that our FC system, operating in a pure oxygen state, outperforms conventional air intake design: heat production increases by 13 %, electric efficiency improves by 20 %, and pure water savings reach 65.57 %. The air compressor witnesses a substantial 37.63 % reduction in power consumption, contributing to an overall energy efficiency increase of 8.92 % for the IHEUS.

Stack performance classification and fault diagnosis optimization of solid oxide fuel cell system based on bayesian artificial neural network and feature selection

Solid oxide fuel cell (SOFC) has attracted much attention because of its high efficiency and silent power generation, and can be applied to the field of fuel cell-powered unmanned boats. However, a fuel deficit failure in the system can lead to reduced stack performance, reducing the reliability of SOFC applications in the field of unmanned boats. Therefore, this paper proposes an efficient breakdown diagnosis model for SOFC system fault diagnosis. Firstly, Bayesian artificial neural network is constructed by using the best feature data subset after Relief-F combined with minimum Redundancy Maximum Relevance algorithm feature selecting. Secondly, the correct diagnosis rate under different number of optimal features is calculated, and the best feature combinations are combined to verify. Finally, the particle swarm algorithm selects the optimal hidden neuron count to optimization model. Experimental findings suggest that for correct diagnosis rate, the breakdown diagnosis model based on the optimal number of 3 features can reduce the training time and maintain high accuracy compared with the use of all 34 features. This research result provides a feasible way for the fault diagnosis application of SOFC system power generation in the field of unmanned boats.

Thermal analysis of fuel cells in renewable energy systems using Generative Adversarial Networks (GANs) and Reinforcement learning

This research introduces a novel in silico thermal management strategy for fuel cell systems that combines Generative Adversarial Networks (GANs) and Reinforcement Learning (RL). The framework utilises the unconditional generation ability of GANs to produce realistic thermal management, which can be used to train an RL agent to control system parameters dynamically. A GAN can be trained on historical data or simulation results to generate realistic and diverse scenarios of the complex relationship between the working point and the thermodynamics of a fuel cell. Once the adversarial network is trained to output realistic data, it can feed an RL agent that tunes the parameters influencing cooling, such as coolant flow rates, air stoichiometry or reactant humidification in response to a generated working point. We conduct experiments and simulations to show that GANs can improve the performance and resilience of RL agents to uncertainty. This approach can be applied to a real-world system, demonstrating significant thermal efficiency, durability and robustness improvements. Adopting such a strategy for thermal management in a fuel cell system is just one example of a new class of intelligent, data-driven control approaches that will enable improved understanding and behaviour of systems, leading to better performance and reliability.

Application of Multiple Linear Regression and Artificial Neural Networks in Analyses and Predictions of the Thermoelectric Performance of Solid Oxide Fuel Cell Systems

Application of Multiple Linear Regression and Artificial Neural Networks in Analyses and Predictions of the Thermoelectric Performance of Solid Oxide Fuel Cell Systems

Numerical analysis and parametric optimization of a direct ammonia solid oxide fuel cell system integrated with organic Rankine cycle

In this study, to maximize the electrical efficiency of the direct ammonia solid oxide fuel cell (SOFC) system, anode-off gas is recirculated for enhancing the system fuel utility and the system exhaust heat is utilized for the organic Rankine cycle (ORC) generating additional electricity. To confirm the superiority of the anode-off gas recirculation (AOGR) SOFC–ORC hybrid system, its electrical efficiency has been compared with two reference systems such as the stand-alone SOFC system without AOGR and the stand-alone AOGR SOFC system. A numerical model on three systems has been developed using Aspen Plus® and validated. Parametric analysis of the three systems has been conducted by varying the operating parameters such as the pump pressure, current density, AOGR ratio, condensation ratio, and fuel utilization. The AOGR SOFC-ORC hybrid system has the highest electrical efficiency among the three types of systems, 70.92 % under nominal conditions. The optimal operational range for the AOGR SOFC-ORC hybrid system has been revealed. As an ammonia-fueled distributed power generation, the proposed system can contribute to achieving net zero in countries where renewable energy is not abundant. This study can provide fundamental insights for establishing an optimization of direct ammonia SOFC systems.

Simulation analysis of BOP thermal management system for hydrogen fuel cell bus

Hydrogen fuel cell bus has been rapidly developed. As an important part of the hydrogen fuel cell system, its BOP (Balance of plant) mainly includes air compressor, controller, and intercooler. In practical applications, the BOP thermal management system generally includes separated cooling circuits. This study proposes an integrated BOP thermal management system, in which the air compressor, the controller and the intercooler share the same cooling circuit. A 1-D numerical model is built in this paper. On the basis of the model, the 13 possible layout schemes of cooling circuit are investigated. Additionally, the BOP temperature variation characteristics under the UDDS (Urban Dynamometer Driving Schedule) condition are also analyzed. The results indicate that not all layouts of integrated scheme can meet the cooling requirements. To meet cooling requirements of the whole BOP, the coolant should pass through the intercooler first in the serial schemes. As for the parallel schemes, the air compressor should be in a single branch, and the controller and the intercooler should be in series successively at another branch. Under the same total flow rate, the average temperature of BOP in the series scheme can be lower than that in parallel scheme by 8 %. In the three components, the intercooler is most affected by the stack power. This study provides reference for the design of the BOP thermal management system.

Degradation Studies of Fuel Cell Cathode Catalyst Layers Using Machine Learning

Fuel cells are a promising technology that has the potential to significantly revolutionize the energy sector by providing clean and sustainable sources of power for transportation, aerospace, and electricity applications. However, optimizing the performance of these devices remains a significant challenge as it largely depends on the catalyst layer in the electrodes of these devices, composed of carbon-supported Pt nanoparticle catalyst (Pt/C), perflurosulfonic acid (PFSA), ionomer binder, and a solvent. The catalyst layer design and operation require extensive knowledge of complex physical and chemical processes especially when achieving a low (<0.1 mgcm-2) Pt loading.Furthermore, the degradation of fuel cells is usually associated with either mechanical and/or electrochemical processes of the catalyst layer during operations, ultimately resulting in performance loss. While combinations of factors are responsible for the degradation of the catalyst layer in the fuel cell electrodes, it is still challenging to evaluate which factor contributes the most to the degradation of the catalyst layer.Machine learning algorithms, being powerful tools for predicting and optimizing the behavior of systems can be used to model complex processes, identify optimal operating compositions, and conditions, and reduce the laborious time and cost required for experimentation. They can be used to analyze data obtained from various experiments to identify patterns, trends, and anomalies. In this study, machine learning algorithms are employed for the prediction of catalyst layer degradation. Furthermore, an assessment of feature importance is conducted, elucidating the relative contributions of individual features to the degradation of catalyst layers. Leveraging on machine learning, we can develop an efficient, reliable, and cost-effective fuel cell system.

Advanced Alkaline Amine Fuel Cell Development

Today, perhaps the most pressing issue is that of power generation. It is important that a source which is inexpensive, reliable, efficient, sustainable, and carbon free be developed and implemented. The hydrogen fuel cell is one possibility. Fuel cells meet many of the requirements listed above save one, current designs are expensive. The catalysts used in most modern hydrogen fuel cells are often platinum group metals, which significantly increases the cost of manufacturing. The high price has proved a significant barrier to adoption. Alkaline fuel cells are comparatively cheap as the catalysts are inexpensive, but they suffer from reliability issues. For one, they form carbonates, which are produced when carbon dioxide reacts with the potassium hydroxide electrolyte. Carbonates build up on the catalytic sites, rendering the fuel cell inoperable. With this project, the chemistry is being manipulated to eliminate this failure. The standard electrolyte is being replaced with an organic amine. Carbonates are soluble in amines and will not precipitate out of solution. This will prevent the buildup and may clean catalytic sites. This project is also testing low-cost production processes. We are using electrochemical synthesis methods to deposit nickel and silver onto carbon cloth to build the fuel cell electrodes. These are then characterized via SEM, EDAX, and x-ray fluorescence. The purpose of this is to establish what size of particles will afford the maximum catalytic activity. Optimizing particle size will help to improve efficiency and reduce costs. Prototypes will be built to identify the best amine and catalyst samples. By the end of 2024, the first cell will be built and tested. Next year, a full-scale alkaline amine fuel cell system will be built. It will be tested as a twelve-volt system for current density, lifetime and total costs.

Durability Investigation of Low Pt-Loaded PEM Fuel Cells with Different Catalyst Layer Morphologies

Low-temperature Polymer Electrolyte Membrane Fuel Cells (PEMFCs) emerge as the most promising fuel cell technology for transportation. Despite the growing interest in fuel cell electric vehicles (FCEVs) motivated by their rapid refueling, high power density, and long-range, their commercialization lags behind that of battery electric vehicles (BEVs) and internal combustion engine vehicles (ICVs). Apart from the lack of hydrogen infrastructure, other primary bottleneck lies in the cost-intensive production of essential components, particularly the dependence on noble metals such as platinum (Pt) to achieve high catalytic activity in the catalyst layer (CL). Simultaneously, meeting durability requirements for long-term performance and stability proposes another challenge. Therefore, enhancing the durability of PEM fuel cell systems without compromising performance and cost presents a significant challenge which stems from the trade-off relationships among these factors. The current target set by the U.S. Department of Energy (DOE) is achieving a durability of 8,000 hours of operation time, meaning 15,000 miles of driving, with less than 10% performance degradation using a 0.1 mg/cm2 Pt-loaded catalyst.The CL is a complex, heterogeneous structure composed of multiple components with different functionalities, and the electrochemical reaction takes place at the interfaces of the components. Several requirements are essential for the CL, including the presence of highly-dispersed Pt sites with high catalytic activity, a continuous path for efficient proton transport and electron conduction, and a through-connected pore network facilitating gas transport and water removal. Extensive research has been directed toward reducing Pt loading in the CL , motivated by the high cost and limited availability of Pt. At low Pt-loadings, researchers detailed the increased oxygen transport resistance within the CL, which is attributed to the reduction of active sites, as well as the heightened flux of reactants near each active site [1]. Therefore, optimizing the CL, both in terms of mass transport and reaction rate, as well as meeting economic and technical requirements, poses a significant challenge. While the impact of CL compositions on the cell performance is studied previously [2][3], systematic investigations are necessary to reveal the effect of CL characteristics on the electrode degradation. The understanding of performance losses during degradation processes is necessary for optimizing the CL for long-term operation and reducing Pt-loading in the cathode without compromising cell durability.This work aims on tailoring the impact of CL characteristics on electrode degradation for low Pt-loaded cells. To achieve this, five different samples with distinct CL features including Pt-loading, CL thickness, Pt/C ratio, and dilution ratio are fabricated. The samples are fabricated using the catalyst-coated membrane approach to suppress interfacial resistances between the membrane and the ionomer in the CL. In addition, a novel ultrasonic deposition method is employed to develop uniform and ultra-thin CLs enabling precise control of the CL thickness. With the use of an accelerated stress test (AST) ranging within 0.6-1 V in an air/H2 environment, the performance loss of the samples at the beginning-of-life (BOL), end-of-life (EOL) and at different stages during the applied AST is investigated. This experimental study serves as a foundational exploration into comprehending the individual impacts of CL compositions on electrode degradation and establishes the framework for the design of durable low Pt-loaded PEM fuel cells.

Open Circuit Voltage Hold Induced Degradation Under Dry Conditions and Recovery Strategies in PEMFC Electrodes

With regards to the decarbonization of the transportation sector in the near future, the importance of proton exchange membrane (PEM) fuel cells is shifting more and more from light-duty vehicles to heavy-duty vehicles, as well as to an application for maritime and aviation applications. With this change in the field of application, the requirements of the fuel cell system need to be adjusted towards an increased fuel efficiency and lifetime.1 Especially the targeted durability of 25,000 h for heavy-duty vehicles requires a detailed understanding of the degradation processes within the stack to be able to minimize performance losses or possible failure of the components.2 During the life cycle of a fuel cell electric vehicle, the stack encounters operation under increased temperature as well as under low relative humidity (RH). Both conditions are well known to lead to a degradation of the membrane electrode assembly (MEA).3,4 Deliberate operation under those conditions and at open circuit voltage (OCV) is commonly used to study the chemical degradation of the membrane. Here it is believed that gas crossover can lead to the formation of radicals, which attack the perfluoro sulfonic acid based ionomer chains and result in a variety of degradation products.5,6 Especially sulfonate group containing degradation species strongly adsorb on the Pt surface and reduce the oxygen reduction reaction (ORR) activity of the cathode catalyst. It was already shown that a suitable recovery step can restore of most of the observed performance losses.3,5 This work focusses on the chemical degradation and subsequent recovery strategies of a commercial MEA with an active area of 5 cm2 and a cathode loading of 0.4 mgPt/cm2. Although it is known that radical scavengers, like Ce3+ cations, minimize the chemical degradation within the membrane, we decided to use an MEA with a non-mitigated membrane (i.e., free of radical scavengers) in order to facilitate the degradation processes.5 As seen in the upper panel of Figure 1, the applied OCV hold for 72 h under H2/air (1000/1000 nccm) at 95 °C and at 30 % RH induces a voltage loss of ~115 mV (at 2.5 A/cm²) in the polarization curve after this accelerated stress test (AST), i.e., at end-of-degradation (EOD; red line/symbols), compared to the initial MEA performance at beginning-of-test (BOT; black line/symbols). In order to distinguish between reversible and irreversible losses, a subsequent recovery step at fully humidified conditions is implemented. The polarization curve at end-of-test (EOT; green line/symbols), i.e., after the recovery step, reveals that the majority of the observed losses is reversible. Provided that the applied recovery step accounts for all reversible effects, the remaining losses of ~45 mV (at 2.5 A/cm²) are of irreversible nature. On the one hand, those irreversible losses partially arise from a small increase in the high frequency resistance (HFR), which rises during the degradation period by ~2 mΩcm² (lower panel of Figure 1. On the other hand, the electrochemically active surface area (ECSA) is reduced by ~20 % over the course of the experiment, which leads to another unavoidable loss in performance. The comparison of the catalyst’s specific activity in units of mA/cm2 Pt, hence, accounting for the loss in ECSA, strongly suggests that the Pt surface at EOT approaches the initial state at BOT, which indicates a reversible degradation mechanism. References A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers and A. Kusoglu, Nat. Energy, 6(5), 462–474 (2021).Marcinkoski, R. Vijayagopal, J. Adams, B. James, J. Kopasz, R. Ahluwalia, Hydrogen Class 8 Long Haul Truck Targets, DOE Hydrogen Program Record# 19006, https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf (2019).Du, T. A. Dao, P. V. J. Peitl, A. Bauer, K. Preuss, A. M. Bonastre, J. Sharman, G. Spikes, M. Perchthaler, T. J. Schmidt and A. Orfanidi, J. Electrochem. Soc., 167(14), 144513 (2020).Jomori, K. Komatsubara, N. Nonoyama, M. Kato and T. Yoshida, J. Electrochem. Soc., 160(9), F1067–F1073 (2013).Zhang, B. A. Litteer, F. D. Coms, R. Makharia, J. Electrochem. Soc., 159(7), F287–F293 (2012).A. Yandrasits, S. Marimannikkuppam, M. J. Lindell, K. A. Kalstabakken, M. Kurkowski and P. Ha, J. Electrochem. Soc., 169(3), 34526 (2022). Acknowledgements We gratefully acknowledge funding from the German Federal Ministry for Digital and Transport (BMDV) under the funding scheme H2Sky (funding code 03B10706). Figure 1

(Digital Presentation) Improvement of Oxygen Reduction Activity on Ti Oxide-Based Electrocatalyst

For widespread utilization of fuel cell system in the future, we have focused on non-precious metal electrocatalyst against high cost of system. Especially, we have studied and reported group 4 and 5 metal oxide-based electrocatalyst as non-platinum catalysts for the oxygen reduction reaction (ORR) because of low-cost, abundant reserves, and high stability in acidic electrolytes [1-2]. We have found excellent ORR activity of Zr oxide-based electrocatalysts prepared from pyrazinecarboxylic acid as a precursor [3-4]. In the case of Ti oxide-based electrocatalysts, the sample prepared under low partial pressure of oxygen with the heat treatment shows high ORR activity when it uses nitrogen-containing porphyrin cyclic organic Ti complexes (TiOTPPz) with multi-walled carbon nanotubes (MWCNTs) as a precursor. However, the heat treatment conditions have not widely investigated yet [5]. In this study, we have investigated to improve ORR activity of Ti oxide-based electrocatalyst prepared from TiOTPPz by varying the oxygen concentration during heat treatment.Oxytitanium tetrapyrazinoporphyrazine (TiOTPPz, [TiOC24H8N16]), a porphyrin cyclic nitrogen-containing organic Ti complex, was used as a starting material. 0.39 g of TiOTPPz and 0.26 g of MWCNT were mixed and treated in a dry ball mill for 1 h to obtain the precursor. The precursor was heated up to 900 oC in an Ar atmosphere and then annealed at 900 oC for 3 h in a low-oxygen atmosphere to obtain a catalyst with precipitated carbon and Ti oxide dispersed on the MWCNTs. The conditions of the hypoxic atmosphere were 2 %H2 + n %O2 / inert gas, with n = 0.05, 0.1, 0.5, 1.0, and 2.0. Catalysts are denoted by TiCNO_(O2 concentration during heat treatment). The catalyst powder was dispersed into 1-propanol with Nafion solution to prepare a catalyst ink. The ink was dropped on a glassy carbon rod, and dried for an hour to use as a working electrode in electrochemical measurement.Electrochemical measurements were performed in 0.5 mol dm-3 H2SO4 at 30 oC with a conventional 3-electrode cell. A reversible hydrogen electrode (RHE) and a glassy carbon plate were used as used as a reference and counter electrode, respectively. Slow scan voltammetry (SSV) was performed at a scan rate of 5 mV s-1 from 0.2 V to 1.2 V vs. RHE under O2 and N2. The ORR current (i ORR) was determined by calculating the difference between the current under O2 and N2.Figure 1 shows oxygen reduction activity of Ti oxide-based electrocatalyst. The vertical axis shows the |i ORR@0.8 V|. The |i ORR@0.8 V| was less than 100 mA gcat -1 at O2 concentrations of 0.05 and 0.1 %, and was greatest at 0.5 % at 413 mA gcat -1. The concentration of O2 further decreased with increasing O2 concentration, and was the smallest at 2.0%. It is suggested that the O2 concentration during heat treatment may have an optimum value around 0.5%.We have also analyzed the catalysts by the XRD before electrochemical measurements. According to XRD spectra, the presence of TiC0.3O0.7 was confirmed in all catalysts. In Ti-CNO_0.5 %, the most active catalyst, the diffraction peaks identified TiO2 rutile and TiO2 anatase were observed. In the case of Ti-CNO_1 and 2 %, the peak intensities of TiO2 anatase increased and the ORR activity decreased. This indicates that the degree of Ti oxidation can be controlled by the atmosphere during heat treatment.Acknowledgement: The authors thank for providing TiOTPPz from Dainichiseika Color & Chemicals Mfg. Co., Ltd.Reference[1] A. Ishihara, Y. Ohgi, K. Matsuzawa, S. Mitsushima, and K. Ota, Electrochim. Acta, 55, 8005 (2010).[2] A. Ishihara, S. Tominaka, S. Mitsushima, H. Imai, H. Imai, O. Sugino, and K. Ota, Curr. Opin. Electrochem., 21 , 234 (2020).[3] Y. Takeuchi, K. Matsuzawa, T. Nagai, K. Ikegami, Y. Kuroda, R. Monden and A. Ishihara, Bull. Chem. Soc. Jpn., 96, 175 (2023).[4] Y. Takeuchi, K. Matsuzawa, Y. Matsuoka, K. Watanabe, T. Nagai, R. Monden and A. Ishihara, Electrochemistry, (2023) in press[5] T. Hayashi, A. Ishihara, T. Nagai, M. Arao, H. Imai, Y. Kohno, K. Matsuzawa, S. Mitsushima and K. Ota, Electrochim. Acta, 209, 1 (2016). Figure 1

Direct Hydroquinone Fuel Cells

The Increasing interest and need to shift to sustainable energy give rise to the utilization of fuel cell technologies in various applications. The challenging task of hydrogen storage and transport led to the development of liquid hydrogen carriers (LHC) as fuels for direct LHC fuel cells, such as methanol in direct methanol fuel cells (DMFC). Although simpler to handle, most direct LHC fuel cells suffer from durability and price issues, derived from high catalysts’ loadings and by-products of the oxidation reaction of the fuel. Herein, we report on the development of direct hydroquinone fuel cells (DQFC) based on anthraquinone-2,7-disulfonic acid (AQDS) as an LHC. We have shown that DQFC can operate with continues flow of quinone as a hydrogen carrier, outperforming the incumbent state-of-the-art DMFC by a factor of three in peak power density, while completely removing the need for any catalyst at the anode. In addition, we demonstrate that the quinone can be charged with protons in the same system, making it a reversible fuel cell system. We optimized the operating conditions and will discuss the governing conditions to reach best performance.