Proton Exchange Research Articles

Performance and economic study of a novel high-efficiency PEMFC vehicle thermal management system applied for cold conditions

This paper proposes three different heating management systems, sysse (self priming thermal management system), syslow (low temperature thermal management system), and syssp (split flow thermal management system), which are mainly composed of PEMFC and heat pump subsystems. Simulations were conducted to compare the comprehensive performance of these systems under cold startup and cold operating conditions, and analyzed the effect of different factors on these three system. The results show that under the influence of cell stack parameters, compared to sysse and syslow, the syssp has an average power consumption reduction of 29.95 % and 20.94 %, with a maximum power reduction of 31.46 % and 27.61 %, the average range power increases by 35.09 % and 23.58 %, with a maximum range power increase of 107.53 % and 75.57 %, the average COPPEMFC (Coefficient of Performance of heating Proton Exchange Membrane Fuel Cell) increases by 0.56 and 0.37. Under the influence of heat pump parameters, the evaporating temperature has a larger impact on the performance gains of the syssp, while condensing temperature has a greater effect on power consumption, range power, and COP variations. Compared to sysse and syslow, the syssp can recover costs as quickly as 3.12 and 3.68 years.

Enhanced Corrosion Resistance in Aluminum-Based Electrolyzer Components via Stoichiometry Tuned Atomic Layer-Deposited TiOx Films.

Titanium (Ti) is widely used as anode current collectors in proton exchange membrane (PEM)-based water electrolyzers due to its self-passivated oxide layer, which protects it from corrosion in acidic solutions. However, the cost of the material and machining process for Ti is high. A wider utilization of water electrolyzers to produce hydrogen could be favored by the use of less expensive coated aluminum (Al) substrates, which could potentially replace high-cost Ti-based components. It is shown here by depositing a pinhole-free oxygen vacancy-rich titanium oxide (TiOx) protection layer by atomic layer deposition (ALD), the corrosion resistance of Al substrates in acidic environments at oxygen evolution potentials can be enhanced. The optimization of the oxygen vacancy concentration is accomplished by tuning the ALD parameters to achieve ideal stoichiometry and conformal coating on rough substrates. The robustness of the coatings was evaluated at high potentials (2.4 V vs NHE = normal hydrogen electrode) in low pH conditions. A low TiOx dissolution rate of the order of ∼6 nm year-1 was observed. By testing under industrially relevant conditions, i.e., high applied voltages (2.4 V) and low pH, an Al loss at around the zero ppb level was achieved using optimized ALD parameters. It is proposed that a 40 nm TiOx coating on Al may be adequate to provide 60,000 h of durability in a PEM water electrolyzer anode current collector.

A new nanocomposite membrane based on sulfonated polysulfone boron nitride for proton exchange membrane fuel cells: Its fabrication and characterization

Sulfonated polysulfone (SPSf) polymer is an alternative raw material in producing commercially used proton exchange membranes. On the other hand, hexagonal boron nitride (hBN) is one of the additives of interest for nanocomposite PEMs. In this study, nanocomposite membranes is fabricated and characterized with SPSf and hBN nanoparticles. The degree of sulfonation of the sulfonated polysulfone is determined by titration, and sulfonic acid bonds are investigated by Proton Nuclear Magnetic Resonance (1H NMR) analysis. SPSf is dissolved with dichloromethane, and hBN nanoparticles are added. After homogenizing the prepared solution with magnetic and ultrasonic stirrers, membranes are formed using Dr. Blade. 1H NMR, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), X-Ray Diffractometer (XRD), and Thermogravimetric Analysis (TGA) analysis are examined the morphological, thermal, and organic compound structures of the membranes. Water uptake capacity, swelling ratio, proton conductivity, oxidative resistance, and mechanical properties of the membranes are determined. The highest water uptake capacity is obtained as 40.08 % in the membrane named SPSf-3 %hBN. Using hBN additive improved swelling ratio and thermal and mechanical strength properties. The proton conductivity values of polysulfone (PSf), SPSf, SPSf-1 %hBN, SPSf-2 %hBN, and SPSf-3 %hBN membranes are determined as 2.89, 6.84, 3.57, 10.8 and 5.12 mS cm−1, respectively. As a result of the analysis, it is observed that the nanocomposite membrane structure has both amorphous and crystalline homogeneous structure.

Developing Catalysts for Membrane Electrode Assemblies in High Performance Polymer Electrolyte Membrane Water Electrolyzers.

Extensive research is underway to achieve carbon neutrality through the production of green hydrogen via water electrolysis, powered by renewable energy. Polymer membrane water electrolyzers, such as proton exchange membrane water electrolyzer (PEMWE) and anion exchange membrane water electrolyzer (AEMWE), are at the forefront of this research. Developing highly active and durable electrode catalysts is very important for commercializing these electrolyzers. However, most research is conducted in half-cell setups, which may not fully represent the catalysts' effectiveness in membrane-electrode-assembly (MEA) devices. This review explores the catalysts developed for high-performance PEMWE and AEMWE MEA systems. Only the catalysts reporting the MEA performance were discussed in this review. In PEMWE, strategies aim to minimize Ir use for oxygen evolution reaction (OER) by maximizing activity, employing metal oxide-based supports, integrating secondary elements into IrOx lattices, or exploring non-Ir materials. For AEMWE, the emphasis is on enhancing the performance of NiFe-based and Co-based catalysts by improving electrical conductivity and mass transport. Pt-based and Ni-based catalysts for hydrogen evolution reaction (HER) in AEMWE are also examined. Additionally, this review discusses the unique considerations for catalysts operating in pure water within AEMWE systems.

A temperature fluctuation suppression control method of fuel cell vehicles to reduce hydrogen consumption

During the driving of the fuel cell vehicles, temperature fluctuations occur in the Proton Exchange Membrane Fuel Cell (PEMFC), whose output efficiency decreases and hydrogen consumption increases. Rule-based (RB) and proportional-integral-derivative (PID) controllers can roughly suppress the temperature fluctuation, but they cannot perform multi-objective optimization, which cannot reduce hydrogen consumption at the same time. To solve this problem, in the first step of this paper, the hydrogen consumption factor and the temperature fluctuation factor in the operating temperature control are introduced to design the DDQN controller. In the second step of this paper, the DDQN controller is trained offline and verified under simulation conditions. The simulation results show that compared with the RB controller and PID controller, the average temperature fluctuation of the DDQN controller is reduced by 27.27 % and 28.50 %, and the hydrogen consumption is saved by 1.78 % and 2.58 %, respectively. The research in this paper is innovative in that it reduces the hydrogen consumption of PEMFC and improves the driving range of fuel cell vehicles from a specific point of view.

An event-triggered and dimension learning scheme WOA for PEMFC modeling and parameter identification

Aiming at the high dimension and complexity of parameters identification problem, a whale optimization algorithm based on event-triggered and dimension learning scheme (EDWOA) is presented, which is specifically designed for the proton exchange membrane fuel cell (PEMFC) model. Drawing inspiration from group optimization strategies, a novel dimensional learning method is introduced to enhance the dynamic search capabilities of the algorithm. To assess the efficacy of the proposed algorithm, benchmark function testing was conducted, and its fitness surpassed common heuristic algorithms on over 15 objective functions. The results clearly indicate that the EDWOA algorithm outperforms its counterparts in terms of global search performance. Its ability to navigate complex search spaces sets it apart from other algorithms. Finally, the proposed EDWOA algorithm is successfully applied to parameter identification in the PEMFC model. Through a comparative analysis with existing research findings, it was found that the identified PEMFC model exhibited a notable enhancement in fitness, ranging from 0.02 to 0.93. This underscores the effectiveness of the EDWOA algorithm in improving the performance and dynamic output of PEMFC models.

Ni/Graphene Coating for Enhanced Corrosion Resistance of Metal Foam Flow Field in Simulated PEMFC Cathode Environment.

Metal foam flow field suffers serious corrosion issues in proton exchange membrane fuel cells due to its large surface area. Ni and Ni/graphene coatings are prepared under constant and gradient current modes, respectively, to improve the corrosion resistance. The effect of the electrodeposition current mode and the deposition mechanism is studied. Compared with Ni coating, Ni/graphene coating brings low corrosion current density and high coating resistance, effectively enhancing the stability of Ni foam in an acidic environment. Different from Ni coating with a single layer, Ni/graphene deposits have core-shell structure, with graphene coated on the surface of Ni nanoparticles. It is shown that graphene deposits cover the Ni particles during the electrodeposition, which protects nickel particles from agglomeration and forms an inert film on the surface of the porous structure. After an 8 h constant potential test, no significant pitting is observed on the surface of Ni/graphene coating, showing excellent anticorrosion performance. As to the effect of the deposition current mode, it is shown that more composite particles deposit on the upper layer under the gradient current mode, which brings denser protective film and fewer surface defects on the surface. Ni/graphene coating electrodeposited under a gradient current mode between 0 and 10 mA·cm-2 exhibits the lowest corrosion current densities. The values at 50 and 80 °C are only 62.9 and 26.0% of those of uncoated Ni foam, respectively.

Construction of X-Co-tri@SSNF reinforced PPS composite proton exchange membranes and their performance in fuel cells

In this study, we pioneered the introduction of benzophenone (DPK) as a solid solvent into polyphenylene sulfide (PPS) melt-blown, which effectively reduced the PPS melt-blown processing temperature and significantly improved the coefficients of variation of PPS melt-blown nonwoven materials. X-Co-tri@SSNF proton exchange membranes with excellent performance were prepared by functionalized modification of PPS melt-blown fabric as a substrate. The structure and properties of X-Co-tri@SSNF proton exchange membranes were systematically characterized. The results demonstrate that the 1-Co-tri@SSNF PEM exhibited a high proton conductivity of 0.183 S cm−1 at 80 °C and high humidity, significantly higher than the commercial Nafion 117 (0.135 S cm−1). Due to the heat resistance of PPS itself and the continuous dense network structure substrate of PPS nonwoven fabrics as well as the high compatibility with the membrane casting liquid, the hybrid membrane interfaces were tightly connected, so it makes the hybrid membrane perform better in terms of mechanical stability (tensile strength of 36.7 MPa), methanol permeability (4.78 × 10−7 cm2 s−1), selectivity (16.32 × 104 S s cm−3), and thermal stability (thermal decomposition temperature of around 450 °C). In addition, the 1-Co-tri@SSNF membrane electrode module exhibited excellent single-cell performance with an open-circuit voltage of 629.91 V and a peak power density of 96.29 mW cm−2 (162.9 % higher than that of Nafion 117). Therefore, the composite PEM with PPS melt-blown fabric as the matrix has a more environmentally friendly process than the commercial Nafion 117 membrane, a theoretical guidance for advancing the large-scale production of low-cost PEM.

Semimetal-triggered covalent interaction in Pt-based intermetallics for fuel-cell electrocatalysis

Abstract Platinum-based intermetallic compounds (IMCs) play a vital role as electrocatalysts in a range of energy and environmental technologies, such as proton exchange membrane fuel cells (PEMFCs). However, the synthesis of IMCs necessitates recombination of ordered Pt-M metallic bonds with high temperature driving, which is generally accompanied by side effects for catalysts’ structure and performance. In this work, we highlight that the semimetal atoms can trigger covalent interactions to break synthesis-temperature limitation of platinum-based intermetallic compounds and benefit for fuel-cell electrocatalysis. Attributed from partial fillings of p-block in semimetal elements, the strong covalent interaction of d-p π backbonding can benefit the recombination of ordered Pt-M metallic bonds (PtGe, PtSb and PtTe) in the synthesis process. Moreover, this covalent interaction in metallic states can further promote both electron transport and orbital fillings of active sites in fuel cells. The semimetal-Pt IMCs were obtained with a temperature 300 K lower than that needed for the synthesis of metal-Pt intermetallic compounds and reached the highest CO-tolerant oxygen reduction activity (0.794 A mg−1 at 0.9 V and 5.1% decay under CO poisoning) among reported electrocatalysts. We anticipate that semimetal-Pt IMCs will offer new insights for rational design of advanced electrocatalysts for fuel cells.

Determination Of Two-Phase Flow Regimes Of A Condensing Water-Air Mixture In An Array Of Micro Channels

Proton exchange membrane (PEM) full cells (FCs) are a promising alternative to combustion engines for mobile applications. Their signature low operating temperature leads to the possible existence of product water in its liquid form. Liquid water formation and transport are important phenomena to understand and model in order to facilitate the development of new, more efficient PEMFCs. This contribution investigates the two-phase flow phenomena separately by introducing a gaseous air-vapor mixture into an optically accessible fuel cell flow plate with 14 parallel micro channels (confinement number Co = 7.3) and a carbon paper inlay representing the FC's gas diffusion layer and bringing it to the point of onset of condensation. Special care is taken to provide a controlled and reproducible air-vapor mixture with low pressure pulsation. One key feature of the experiment is that the flow plate used is designed to be as similar to a regular research fuel cell flow plate as possible, retaining its channel surface properties and electrical parameters. It can also be heated to a given temperature to mimic the fuel cell operating conditions. Therefore, the same plate can also be used in in-situ experiments in an operated fuel cell. An air mass flow rate of 500 - 1000 mLn / min with relative humidities of 75% - 95% at 65°C and 75°C was investigated. The emerging flow patterns were captured using a high-speed camera at 250 Hz and categorized using canonical two-phase flow regime nomenclature. It is shown that the present setup can produce the relevant two-phase flow patterns that can be found in operated fuel cells as reported by previous studies and is furthermore equipped to investigate flow states not easily reached with an operated fuel cell (e.g. flooded channels).

Phase-controlled synthesis of starch-derived Mo2C–MoC/C heterostructure catalyst for electrocatalytic hydrogen evolution reaction

The electronic structure of molybdenum carbide closely resembles that of Pt, making it a promising candidate material for replacing noble metal catalysts. However, the primary challenge is the controlled and eco-friendly synthesis of molybdenum carbide. Herein, we developed a sustainable and controlled method for synthesizing a heterostructure catalyst for the electrocatalytic hydrogen evolution reaction (HER) using starch as the raw material. Through a hydrothermal redox reaction and subsequent temperature-programmed treatment under an inert atmosphere, the hexagonal Mo2C-cubic MoC heterostructure nanoparticles were dispersed on a carbon matrix. Our investigation into the synthesis process extensively covered the growth of MoO2 nanocrystals and hydrochar during the hydrothermal redox reaction, as well as the phase evolution during the subsequent temperature-programmed treatment. Electrochemical assessments demonstrated the catalyst's remarkable efficiency for the hydrogen evolution reaction across both acidic and alkaline media, achieving a current density of 10 mA/cm2 with an overpotential of 139.4 mV in 1 M KOH solution and 160.7 mV in 0.5 M H2SO4 solution. Combining a series of electrochemical characterizations and applying the distribution of relaxation times (DRT) analysis to operando electrochemical impedance spectroscopy (EIS) data, the superior kinetic performance of the Mo2C–MoC/C was demonstrated, outperforming that of single-phase molybdenum carbide. Furthermore, the catalyst has demonstrated remarkable stability even at high current densities in both acidic and alkaline electrolytes, underscoring its potential as a cathode catalyst in both alkaline water electrolyzers and proton exchange membrane (PEM) electrolyzers.

Rotordynamics of a rotor supported by foil bearings under various housing excitation

Proton Exchange Membrane (PEM) Fuel cell Systems(FCS) are rapid-growing technology in transportation systems. In such applications, a motor-driven oil-free air compressor is one of the critical auxiliary subsystems. Foil bearings are the perfect choice as oil-free bearings for the compressors due to high rotordynamics stability and shock-resistance. The platform of a motor-driven oil-free compressor can also be used as an electric turbocharger for traditional internal combustion engines. All electromechanical subsystems for electric vehicles must satisfy vibration endurance requirements following ISO 16750–3:2012, characterized by certain g-loading at specific frequencies. For the compressor to satisfy ISO 16750 requirement, detailed rotordynamics simulations with externally excited compressor housing under certain g-loading are essential to design the foil bearings considering the static and dynamic loads to the bearing and rotordynamics stability. The main objectives of the current research are 1) to develop a four degree of freedom (4-DOF) dynamic model of the rotor supported by foil bearings under external excitation to the compressor, 2) to simulate linear and non-linear rotordynamics of the compressor rotor supported by two radial foil bearings, and 3) to provide appropriate design guideline such as bump stiffness and axial length of the foil bearings. The simulations show that the rotor is stable for both under single frequency excitation and simultaneous excitations of all the frequencies in ISO 17650 standard. 4-DOF modal analyses were applied to identify natural mode of the system under the housing excitation.

Life prediction for proton exchange membrane fuel cell based on experimental results and combinatorial optimization algorithm

The durability is a key factor of fuel cell in large-scale application of automobiles. It is great important to real the lifetime and health status of fuel cells, especially in vehicle driving conditions. Based on the experimental data, this paper used the model-based method and data-driven method to predict the life of fuel cells, respectively. The model-based method established the equivalent circuit model according to the mapping law of electrochemical impedance spectroscopy (EIS) and the parameters of the equivalent circuit model were identified by newly considering the phenomenon of voltage recovery, revealing the strong linear correlation between impedance and voltage. The data-driven method selected a combinatorial optimization PSO-LSSVM algorithm and compared it with the prediction results of MATLAB's time series toolbox. The results show the mean square error (MSE), End of Life (EOL) of the model-based method, the time series toolbox and PSO-LSSVM algorithm are 0.019, 8.2 × 10−3 and 4.42 × 10−5, the 260h, 438h and 427h, respectively. Comparing with the real EOL of 421h, the error of PSO-LSSVM algorithm is only 6 h, which means the remaining useful life can be predicted with high accurately. Thus this study provides a reference for fault identification and life prediction of fuel cell health management.

ZIF-8-derived nanocarbon composite-based highly active platinum group metal-free bimetallic electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cells

Non-precious metal catalysts are ideal low-cost substitutes of Pt/C for the sluggish oxygen reduction reaction (ORR), despite the serious stability challenges in proton exchange membrane fuel cells (PEMFC) to alleviate the energy crisis and environmental problems. Platinum group metal (PGM)-free bimetallic composite electrocatalysts are assumed to be an interesting route to be investigated to address the stability and ORR selectivity related issues in PEMFC conditions. In this regard, we propose a simple and facile synthesis route by a composite of multi-walled carbon nanotubes and zeolitic imidazolate framework (ZIF)-8 followed by impregnating dual transition metals (FeMn, FeCo, and CoMn) and evaluate their ORR activity in acid media and PEMFC performance. Various catalyst materials are prepared and optimized to achieve the highest electrocatalytic performance. The prepared catalysts are characterized by various physico-chemical methods to elucidate their textural, structural, and morphological properties. The high ORR electrocatalytic activity and selectivity of the catalyst are reported in terms of half-wave potential and low H2O2 yield as determined by the rotating ring-disk electrode method. The significant electrochemical stability under accelerated durability test and high peak power density (787 mW cm−2) in H2-O2 PEMFC made these catalysts as potential candidates for efficient alternatives to PGMs in the fuel cell cathodes.

Stack-level analysis of the performance variation in air-cooled PEMFC with Z-type anode manifold

Air-cooled proton exchange membrane fuel cell (PEMFC) stack holds significant promise due to its potential to reduce system complexity. The anode manifold type leads to gas maldistribution in an air-cooled stack, and affects the efficiency and life span of the stack. In this study, 3D multi-physics model of stacks ranging from 10 to 40 cells are established to investigate the gas distribution characteristic of Z-type anode manifold. Considering the heat dissipation aspects only, it is advisable to keep a thin endplate while meeting the required stress tolerances. The core temperature of the stack with 20 mm endplates measures 43.8 °C, while the stack with 6 mm endplates reaches a core temperature of 45.5 °C. Under a cathode air flow velocity condition of 4 m‧s−1, the maximum net oxygen consumption reaches 1.69 mol‧s−1 in Cell-4. Furthermore, the electrochemical reaction intensity decreases sequentially from Cell-4 and Cell-5 in the middle to Cell-1 and Cell-10 in the edges of the stack. Additionally, cells near the anode inlet and outlet are prone to have the insufficient gas supply in the Z-type anode manifold stack.

Nitrogen, fluorine, and phosphorus tri‐doped porous carbon with high electrical conductivity as an excellent metal‐free electrocatalyst for oxygen reduction reaction

Today’s oxygen reduction reaction (ORR) depends on the precious metal Pt‐based catalysts, limiting the large commercialization of promising energy conversion technologies such as proton exchange membrane fuel cells (PEMFCs) and metal‐air batteries. Therefore, the rational design of low‐cost and highly efficient electrocatalysts for ORR is strongly desired. Herein, we report a porous carbon doped with nitrogen, fluorine, and phosphorus (N, F, P tri‐doped carbon) prepared via only a heating process using low‐cost glycine, ammonium fluoride, and phytic acid as precursors. X‐ray photoelectron spectroscopy (XPS) analysis revealed the existence of pyridinic‐N and the co‐existence of graphitic‐N and oxidized graphitic‐P, which can be active sites, with semi‐ionic C‐F bonds highly boosting ORR activity. Remarkably, the resultant N, F, P tri‐doped carbon exhibited outstanding activity for the ORR with an onset potential comparable to that of commercial 20 wt.% Pt/C catalyst, the half‐wave potential superior to that of the Pt/C catalyst, and the electron transfer number close to 4.

Novel zirconium phosphate/MXene/ionic liquid membranes for PEM fuel cells operating up to 145°C

In this work, zirconium phosphate, MXene, and a hexyl-based ionic liquid were incorporated into a porous PTFE polymer to synthesize novel composite proton exchange membranes (PEM) for fuel cell applications. The synthesized composite membranes were evaluated for their conductivity at temperatures above the boiling point of water as well as their water uptake properties, thermal stability, surface morphology, and structural characteristics via several characterization techniques. It was observed that the inclusion of MXene had a direct impact on the thermal stability of these membranes and caused substantial structural modifications within the membrane’s matrix. The fabricated membranes displayed a high proton conductivity at room temperature, reaching a peak of approximately 10−2 S/cm when all materials were combined. The membranes exhibited good proton conductivity of 10−4 S/cm at high temperature ranges up to 145℃ and appeared to be stable at higher temperatures, as thermogravimetric analyses showed. The results reported here demonstrate the suitability of the MXene-based synthesized membranes for hydrogen-fueled PEM fuel cell applications. This, in turn, will contribute to enhanced energy efficiency and cleaner energy transition.

Reinforcing membranes with subgaskets in proton exchange membrane water electrolysis: A model-based analysis

Ensuring the long-term mechanical durability of perfluorosulfonic acid membranes in proton exchange membrane water electrolysis (PEMWE) is essential for long lifetimes. This study investigates the potential of reinforcing the membrane by incorporating a subgasket layer outside the active area. Thus, experimental tensile measurements with the subgasket material and with the subgasket-membrane composite are conducted to characterize their mechanical properties. The obtained data are used to identify suitable material models and parameterize them by applying a tensile test simulation based on the finite element method. By integrating subgaskets in a structural mechanics PEMWE cell model, the impact of the reinforcement on the membrane stability was investigated. The results indicate that even thin layers of subgaskets stabilize the membrane at the gap interface between the cell frame and the porous transport layer. The level of stabilization is further enhanced when using thicker subgaskets that cover the entire gap. However, one-sided subgaskets exhibit reduced mechanical stabilization. Furthermore, membrane buckling due to an increased gap size can be prevented using a subgasket up to a maximum gap size of 0.45 mm.

Evidence for NMR Relaxation Enhancement in a Protic Ionic Liquid by the Movement of Protons Independent of the Translational Diffusion of Cations.

The molecular dynamics, thermal stability, and ionic conductivity were studied in the protic ionic liquid 1-methylimidazolium bis(trifluoromethylsulfonyl)imide ([MIm][TFSI]). The relaxation of the 1H spin-lattice of cations in the measured frequency range (10 kHz to 20 MHz) and temperature (298 to 343 K) is sensitive mainly to slow processes occurring in the molecular dynamics of protic ionic liquid and dominated by the contribution of intermolecular translational diffusion. Molecular rotations give only a constant contribution and become significant in the higher frequency range. An interesting feature is the observed enhancement of the 1H spin-lattice relaxation below 0.03 MHz attributed to the exchange of protons (order of 10-5 s) between imidazolium cations. The measurements of the self-diffusion coefficient of hydrogen atoms of cation from 298 to 343 K additionally confirm the observed phenomenon. The coefficient for exchangeable protons -NH is higher than for the cation. The nuclear magnetic resonance (NMR) experiments provide unambiguous evidence for proton transport decoupled from molecular diffusion of ions and support the conclusion that the charge transport mechanism in the studied PIL includes contributions from both the vehicular and Grotthus mechanisms. The protic ionic liquid is thermally stable to about 573 K as shown by thermogravimetric analysis and its electrical conductivity is 5 × 10-2 S/cm at 423 K.

Grain Boundary Defect Engineering in Rutile Iridium Oxide Boosts Efficient and Stable Acidic Water Oxidation.

Proton exchange membrane water electrolysis (PEMWE) is considered a promising technology for coupling with renewable energy sources to achieve clean hydrogen production. However, constrained by the sluggish kinetics of the anodic oxygen evolution reaction (OER) and the acidic abominable environment render the grand challenges in developing the active and stable OER electrocatalyst, leading to low efficiency of PEMWE. Herein, we develop the rutile-type IrO2 nanoparticles with abundant grain boundaries and the continuous nanostructure through the joule heating and sacrificial template method. The optimal candidate (350-IrO2) demonstrates remarkable electrocatalytic activity and stability during the OER, presenting a promising advancement for efficient PEMWE. DFT calculations verified that grain boundaries can modulate the electronic structure of Ir sites and optimize the adsorption of oxygen intermediates, resulting in the accelerated kinetics. 350-IrO2 affords a rapid OER process with 20 times higher mass activity (0.61 A mgIr -1) than the commercial IrO2 at 1.50 V vs. RHE. Benefiting from the reduced overpotential and the preservation of the stable rutile structure, 350-IrO2 exhibits the stability of 200 h test at 10 mA cm-2 with only trace decay of 11.8 mV. Moreover, the assembled PEMWE with anode 350-IrO2 catalyst outputs the current density up to 2 A cm-2 with only 1.84 V applied voltage, long-term operation for 100 h without obvious performance degradation at 1 A cm-2.