Electrochemical Active Surface Area Research Articles

Nanoengineered Bifunctional Porous Ni5P4 Electrocatalyst with Accelerated Bubble Departure and Reduced Overpotential for Solar-Driven Water Splitting

To achieve the global "carbon neutral" goal and low-carbon economy by 2050-2100, hydrogen has been considered as an ideal renewable and sustainable energy carrier.1,2 The electrochemical conversion of solar energy to energy dense hydrogen fuel ensures a promising approach to generate a clean and sustainable source of energy.3,4 The integrated solar powered water electrolyzers for green hydrogen production completely eliminate all sources of carbon emissions arising from the direct power supply, towards achieving a low-carbon economy.5,6 However, large-scale solar water splitting for green hydrogen production still remains a challenge due to expensive electrocatalyst. As a low-cost, earth-abundant catalyst Nickel phosphide shows enormous potential to effectively reduce water and generate hydrogen. We propose a low-cost and facile approach to fabricate nanoengineered hierarchically porous Ni5P4 as an electrocatalyst (p-Ni5P4) providing high surface area and enabling fast gas diffusion. Nickel phosphide (p-Ni5P4@NF) has pores ranging from 50-500 nm to 200-600 μm and enlarges the electrochemically-active surface area by 5 times. The porous structure of p-Ni5P4@NF offers abundant cavities to gas nucleation and fast growth of H2 bubble, and small bubbles (10-50 µm) depart quickly owing to reduced contact line. By enhancing gas transfer and reducing bubble overpotential by 30%, p-Ni5P4@NF achieves excellent electrocatalytic performance with a low HER (145 mV), OER (197 mV) and overall water splitting potential (1.54 V) at 10 mA cm-2. Powered by multijunction PV cell, the full electrolytic cell records a high solar-to-hydrogen efficiency of 14.5 %. Keywords: Water splitting; Electrocatalysis; Green Hydrogen; Nickel Phosphide.

Synthesis of Ni-MOF loaded Pt nanoparticle composites for the electro-oxidation of methanol in acidic media

A series of Pt/Ni-MOF nanocomposites with different atom molar ratio of Pt/Ni were synthesized by the traditional hydrothermal method. Various methods including element mapping, X-ray diffraction (XRD) were employed to characterize the crystal structure and surface morphology of the materials. TEM (Transmission Electron Microscopy) confirms that the Pt nanoparticles are highly dispersed onto the Ni-MOF nanosheet surface, which can provide an abundance of active sites for efficient oxidation of methanol. Electrochemical measurements showed that Catalyst b (the atomic molar ratio of Pt to Ni is 2:1 in the precursor materials) exhibited a higher oxidation current density in MOR and larger electrochemically active surface area (ECSA) than other catalysts with different atomic ratios and commercial Pt/C. Meanwhile, the synthesized catalysts showed long-term activity and good resistance to toxicity.

Synthesis of FeNi-based heterostructure on a nickel foam at room temperature for efficient catalyzing hydrogen evolution reaction

The FeNi-based heterostructure was synthesized on a nickel foam by a simple dip-coating method with zero-energy consumption at room temperature. The obtained heterostructure is flower-like and has high-performance for electrocatalyzing the hydrogen evolution reaction (HER). On the FeNi-based heterostructure, the overpotential was only 228 mV at a current density of 100 mA cm−2 in 1 M KOH, and can maintain 10 h stability with chronoamperometry test. The outstanding catalytic activity was attributed to the unique structure with a large electrochemical active surface area and the synergistic effect between different transition metal elements. This research afforded a new way to design low-cost and high-performance HER electrocatalyst.

Assessing Electrocatalyst‐Ionomer Interactions: HOR/HER Activity of Pt/C Catalyst Layers incorporating Poly(imidazolium)s

AbstractIn this work, a specifically designed C2‐protected poly(imidazolium) with a limited number of freely rotating phenyl groups was synthesized and studied as a binder for a commercial Pt/C electrocatalyst. The ionomer‐electrocatalyst interactions were extensively investigated in terms of kinetic and limiting current for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER). A non‐monotonic evolution of the electrochemically active surface area (ECSA) was observed with the increase of the ionomer‐to‐carbon ratio. The addition of ionomer to the catalyst layer leads to an increase in stability and activity of the electrocatalyst during HOR, while substantially increasing the ionomer content leads to only a marginal decrease in ECSA. Potential phenyl adsorption and cation‐hydroxide ion‐water interactions which impart deleterious impact on electrochemical activity are minimized owing to the sterically encumbered design of the polyimidazolium which (i) limits direct molecular interaction of the imidazolium cationic ring with Pt and (ii) encumbers phenyl and imidazolium ring rotation to hinder parallel aromatic ring adsorption onto the electrocatalyst surface, hence mitigating strong adsorption/blocking interactions.

Recent Advances and Future Perspectives of Transition Metal‐Supported Carbon with Different Dimensions for Highly Efficient Electrochemical Hydrogen Peroxide Preparation

AbstractElectrocatalytic oxygen reduction to hydrogen peroxide (H2O2) is one of the most promising methods to replace the conventional anthraquinone route for the green and facile synthesis of H2O2. Owing to the outstanding electrochemical active surface area and fast charge transfer capability of carbon nanomaterials or nanostructures with different dimensions, such as 1D, 2D, and 3D, various strategies including nanostructure engineering, defect engineering, and interface engineering have been proposed to promote the catalytic activity of carbon‐based catalysts toward two‐electron (2e−) oxygen reduction reaction (ORR) for H2O2 generation over the past decade. In this review, the latest progress, major achievements, and prospects of the transition metal‐supported carbon with different dimensions for highly efficient electrochemical H2O2 preparation via the 2e− ORR process are summarized. The rational design principles and synthetic strategies of transition metal‐supported carbon are systematically introduced while the representative advances, the identification of active sites, and their possible catalytic mechanisms toward the H2O2 production are discussed. Finally, according to the current development stage and existing shortcomings of 2e– ORR catalysts for H2O2 production, the challenges and prospects of transition metal‐supported carbon with different dimensions are also summarized.

The determination of the electrochemically active surface area and its effects on the electrocatalytic properties of structured nickel electrodes produced by additive manufacturing

Additively manufactured (AM) nickel electrodes offer a great potential as an efficient solution for oxygen evolution catalysts in alkaline electrolyzers, since advanced fabrication methods allow the design of high surface area electrodes. The accurate determination of the electrochemical active surface area (ECSA) is a key step in the evaluation of the intrinsic catalytic activity of complex electrodes. In this work, we fabricated Ni electrodes with different macroscopic lattice structures using laser powder bed fusion of metals (PBF-LB/M). The selected designs allow exploring the effects of the electrode geometry on the electrochemical performance. X-ray photon spectroscopy (XPS) and a non-contact optical profilometer (NCOP) were used to investigate the composition and surface morphology of the electrodes. The ECSA was determined by three different approaches. 1. Linear and non-linear allometric fitting of the double layer capacitance from voltammetric experiments. 2. Integration of the Ni2+/Ni3+ transition, also from voltammetry. 3. Assessing double layer capacitance determined from electrochemical impedance spectroscopy (EIS) at open circuit potential (OCP) and the adsorption capacitance for the oxygen evolution reaction (OER) intermediates. Comparing these methods, large deviations in the resulting ECSAs were found, motivating a comprehensive discussion. In addition, four different reactions were investigated, ferri-ferrocyanide redox system, hydrogen evolution, ethanol electrooxidation, and oxygen evolution reaction. The obtained results demonstrate the potential of AM to tailor electrode performance by altering electrode geometry. The findings underline the importance of the ECSA determination for the comparison of the electrocatalytic activity in different electrodes.

Development of novel Ce doped ZnO/graphene based sensor for electrochemical investigation of potassium-competitive acid blocker: Vonoprazan

The present study reports the synthesis of a Ce-doped ZnO/r-GO nanocomposite via a conventional hydrothermal route. The synthesized nanocomposites were utilized for the purpose of sensitive and selective detection of vonoprazan (VPN). The composite’s morphological, structural, and electrochemical properties were thoroughly characterized. This study focuses on the utilization of a glassy carbon electrode that has been modified with Ce-doped ZnO/r-GO for the purpose of detecting the potassium-competitive acid blocker VPN, which is commonly used in the treatment of peptic ulcer. The detection methods employed in this study include voltammetric and square wave techniques. The composite material exhibited exceptional efficacy as an electron (e−) transfer mediator during the oxidation of VPN. The modified electrode exhibited a discernible reaction for SWV assessments in relation to VPN identification, achieving a minimal detection threshold of 1.8 × 10−8M and an extensive range of linearity spanning from 2.0 × 10−7 M to 8.0 × 10−6 M, given ideal circumstances. The rate constant for charge transfer (ks) was determined to be 1.17 × 10−6 cm s−1, and an estimation of the electrochemical active surface area yielded a value of 0.081 cm2. The sensor that was artificially created demonstrated favorable selectivity, enduring stability, and notable reproducibility. The sensor has been utilized for the purpose of analyzing human serum and urine samples, yielding favorable recovery outcomes.

Fabrication of Gold Nanoparticles Embedded Laser-Induced Graphene (LIG) Electrode for Hydrogen Evolution Reaction

The advancement of renewable energy technologies like water electrolysis and hydrogen fuel cells relies on the fabrication of effective and reliable catalysts for the hydrogen evolution process (HER). In this regard, we report gold nanoparticles embedded in laser-induced graphene electrodes for regulation of overpotential and electrocatalytic performance of hydrogen evolution reaction. Gold nanoparticles were deposited onto the LIG surface using electrode deposition via cyclic voltammetry (CV) at different cycle lengths. The catalyst fabrication technique enables the manipulation of many electrochemical parameters, such as overpotential value, charge transfer resistance, electrochemical active surface area, and tafel slope, through the adjustment of cyclic voltammetry (CV) cycles. The LIG-Au@50 sample demonstrates remarkable electrocatalytic characteristics, as evidenced by its low overpotential of 141 mV at a current density of 10 mA/cm2 and reduced tafel slope of 131 mV/decade in an acidic environment. Furthermore, the presence of an augmented electrochemical active surface area, a mass activity of 8.80 A/g, and a high turnover frequency of 0.0091 s−1 suggest elevated and significant accessibility to plentiful active sites. A significant decrease in charge transfer resistance resulted in an enhanced rate of the water-splitting reaction.

Promotion of hydrogen evolution from seawater via poly(aniline-co-4-nitroaniline) combined with 3D nickel nanoparticles

This work reports the synthesis of poly (aniline-co-4-nitroaniline) deposited on a three-dimensional nanostructured nickel (3D-Ni) film, where both layers were fabricated via potentiostatic electrodeposition. The obtained electrocatalyst exhibited excellent electrochemical activity for the Hydrogen Evolution Reaction (HER) with small overpotentials of − 195 and − 325 mV at − 10 and − 100 mAcm−2, respectively, and a low Tafel slope of 53.3 mV dec−1 in seawater. Additionally, the electrocatalyst exhibited good stability after 72 h operation under a constant potential of − 1.9 V vs. RHE. The efficient HER performance of the as-prepared catalyst was found to originate from the synergy between the conducting polymer and three-dimensional nickel nanoparticles with a large electrochemical active surface area. Moreover, the results obtained from electrochemical impedance spectroscopy (EIS) measurements revealed that the presence of 3D-Ni layer improved the kinetics of HER by reducing the charge transfer resistance for the electrocatalyst.

Enhancing the electrocatalytic performance of vanadium oxide by interface interaction with rGO and NiO nanostructures for electrochemical water oxidation

The crucial requirement for achieving the high-efficiency industrialization of electrochemical water splitting lies in the development of proficient electrocatalysts designed to moderate the energy barriers associated with both the hydrogen and the oxygen evolution reaction (HER and OER). Improving performance and efficiency is the main objective behind the search for new types of electrocatalysts for electrochemical water splitting. Existing electrocatalysts have limitations, such as high energy barriers and material stability issues, which hinder the overall effectiveness of water splitting. Therefore, the invention of new electrocatalysts with desired performance is desired to overcome these challenges. Herein, an interconnected vanadium oxide-reduced graphene oxide-nickel oxide (VrG/NiO) electrocatalyst is recognized for efficient OER performance. The flower-like spherical structure of V2O5 adhered with NiO on the rGO surface and generated an effective interfacial interaction between the electrocatalyst materials. Among the different combinations, the desired ratio of VrG/NiO electrocatalyst exhibits a lower overpotential (η10 = 155.4 mV) and Tafel slope (84.1 mV.dec−1) for OER in 1 M KOH. The VrG/NiO electrocatalyst showed stable performance after 5000 cyclic voltammetry cycles and chronopotentiometry (15 h) analyses. For overall water splitting, VrG/NiO attained a low cell voltage (1.73V@10mA cm−2). The efficient OER performance attained by the VrG/NiO electrocatalyst is due to its resourceful electrochemical active surface area (Cdl = 43.18 mF cm−2), redox capability, and synergistic effects.

Enhanced nitrogen doping on porous carbon via confining-pyrolysis method for electrocatalytic oxygen reduction

Reasonable design and development of N-doped carbon materials by post-treatment of porous carbon with melamine is an effective route to preparing low-cost and high-performance electrocatalysts toward oxygen reduction reaction. Nevertheless, melamine derivatives have been observed to rapidly escape during pyrolysis, resulting in the undesirable loss of nitrogen atoms and catalytic activity. Here, a confining-pyrolysis method was proposed to accumulate melamine in the micropores of porous carbon to prepare the object N-doped carbon material with an enhanced nitrogen doping. Because the melamine accumulated in the micropores of porous carbon, the object N-doped carbon material shows a significant enhancement in N-atom content, graphitization degree, mesopore volume, electrochemical active surface area and hydrophobic surface. Density functional theory calculations and electrocatalytic tests demonstrate that the object N-doped carbon material delivers a good electrocatalytic oxygen reduction performance. The N-doped carbon electrode displayed a close half-wave potential for alkaline ORR compared to the commercial Pt/C electrocatalyst and showed an excellent cycling stability and methanol tolerance. This work provides a cost-effective method to prepare carbon-based ORR electrocatalyst for energy devices.

Optimizing electronic structure of CoSe2 nanorods via N-dopant modulation for superior electrocatalytic hydrogen evolution reaction

The hydrogen evolution reaction (HER) performance of transition metal selenides (TMSs) based electrocatalysts in alkaline media is severely affected by numerous issues, including structural instability due to surface oxidation reactions, high overpotentials, and sluggish water dissociation kinetics. Here, we present the simple and scalable synthesis of N-doped cobalt diselenide nanoflowers grown on conductive carbon cloth (N-CoSe2/CC). First, Co(OH)F/CC precursor with a well-defined pore structure through the solvothermal method followed by incorporation of Se ions on the Co mAtrix via a chemical vapor deposition method. Porous CoSe2 was further modified by a heteroatom (N) to enhance electrocatalytic activity, high performance might be attributed to the formation of plentiful active sites, synergistic effects, structural modulation, and improved electronic conductivity. The optimal N-CoSe2/CC catalyst exhibits a high electrochemically active surface area (ECSA) and possesses a low working potential of 73 mV (vs. RHE), which corresponds to 10 mA cm−2 current density, and a lower Tafel slope (75 mV dec−1) in an alkaline medium (1.0 M KOH) with longterm stability of 20 h. The outcomes of the experiment aided by DFT calculations demonstrate that doping of N can significantly alter the electronic states of the “Co” d-orbital, boosting HER performance. This study might open up new possibilities for designing anion-doped transition-metal dichalcogenide electrocatalysts for the potential applicability of HER.

Cerium-doped 1 T phase enriched MoS2 flower-like nanoflakes for boosting hydrogen evolution reaction

MoS2 has drawn worthwhile attention in the area of hydrogen evolution reactions (HER) owing to its exceptional catalytic performance. Nonetheless, its activity is still limited by an inert substrate. Thus, doping with rare earth heteroatoms is an effective strategy to maximize its electrocatalytic activity. Here, we utilize a facile hydrothermal approach to synthesize Ce-doped MoS2. The investigation reveals that the amount of Ce doped has an impact on the efficiency of HER. The optimal amount of Ce doped can alter the morphology, defects, and electronic structure of MoS2, and further boosting its HER performance. Ce0.1-MoS2 has a lower overpotential of 113.78 mV in H2SO4 at 10 mA cm−2, with a lower Tafel slope, and ideal electrochemical active surface area. Moreover, the electrocatalyst demonstrates excellent durability for 10 h. This work unveils a dissimilar perspective for the synthesis of excellent HER activity MoS2-based catalysts.

Unveiling Local Aging Patterns Following Accelerated Stress Testing of High-Performance Polymer Electrolyte Fuel Cells.

This study presents an in-depth analysis of heterogeneous aging patterns in membrane electrode assemblies (MEAs) subjected to diverse accelerated stress test (AST) conditions, simulating carbon corrosion (CC AST) and Pt particle size growth in fully humidified (Pt AST-Wet) and underhumidified (Pt AST-Dry) H2/N2 atmospheres. Multimodal characterization techniques are used to focus on heterogeneous aging patterns, primarily examining the variations in current distributions and Pt particle size maps. The findings reveal distinct characteristics of current distributions for all the AST cases, with substantial changes and strong current gradients in the CC AST case, indicative of severe performance degradation. Notably, despite significant differences in Pt particle size growth at the end-of-life (EOL), the Pt AST-Wet and Pt AST-Dry cases show minor changes in spatial current distributions. Moreover, a preferential growth of Pt particles under serpentine flow field bends in the Pt AST-Wet case is observed for the first time. This study provides crucial insights into the role of mass transport properties in shaping fuel cell performance, and highlights the need to consider factors beyond electrochemically-active surface area (ECSA) when assessing fuel cell durability.

ORR Activity and Voltage-Cycling Stability of a Carbon-Supported PtxY Alloy Catalyst Evaluated in a PEM Fuel Cell

Platinum-yttrium alloys (PtxY) are suggested to have superior oxygen reduction reaction (ORR) activity and long-term stability in proton exchange membrane fuel cells (PEMFCs). However, the actual ORR activity and stability of a PtxY catalyst with a high electrochemically active surface area (ECSA) in a PEMFC remains uncertain. Here, a Ketjen black (KB) carbon supported PtxY/KB catalyst with a high ECSA (∼60 m2/g) was synthesized using a carbon nitride precursor. Based on elemental analysis, XRD, electron microscopy, and a mass-balance based model, it was shown that the acid-leached PtxY nanoparticles of the catalyst consist of a ∼0.7 nm thick Pt-shell and a Pt3Y core. Rotating disk electrode (RDE) and 5 cm2 single-cell PEMFC measurements indicated that the ORR activity of the acid-leached PtxY/KB catalyst is similar to an analogously synthesized Pt/KB reference catalyst with the same ECSA. Voltage-cycling accelerated stress tests (ASTs) between 0.6−1.0 V (in H2/N2 at 80 °C/95% RH) in 5 cm2 single-cells showed that the ORR activity and durability of the PtxY/KB catalyst is similar to that of the Pt/KB reference catalyst. Thus, the high durability of Pt-rare Earth alloys that has been claimed on the basis of RDE measurements is not observed in actual PEMFCs.

Degradation of Pt-Based Cathode Catalysts Upon Voltage Cycling in Single-Cell PEM Fuel Cells Under Air or N2 at Different Relative Humidities

A major degradation mechanism of polymer electrolyte membrane fuel cells (PEMFCs) in transportation applications is the loss of the electrochemically active surface area (ECSA) of platinum cathode catalysts upon dynamic load cycling (resulting in cathode potential cycles). This is commonly investigated by accelerated stress tests (ASTs), cycling the cell voltage under H2/N2 (anode/cathode). Here we examine the degradation of membrane electrode assemblies with Vulcan carbon supported Pt catalysts over extended square-wave voltage cycles between 0.6-1.0 VRHE at 80 °C and 30%-100% RH under either H2/N2 or H2/Air; for the latter case, differential reactant flows were used, and the lower potential limit is controlled to correspond to the high-frequency resistance corrected cell voltage, assuring comparable aging conditions. Over the course of the ASTs, changes of the ECSA, the hydrogen crossover current, the proton conduction resistance and the oxygen transport resistance of the cathode electrode, as well as the differential-flow H2/O2 and H2/Air performance at 80 °C/100% RH were monitored. While the ECSA loss decreases with decreasing RH, it is independent of the gas feeds. Furthermore, the H2/Air performance loss only depends on the ECSA loss. ASTs under H2/N2 versus H2/Air only differ with regards to the chemical/mechanical degradation of the membrane.

A holistic physics-based observer for online flooding and ECSA loss detection in FCEV

This paper addresses the critical need for improving fuel cell electric vehicles (FCEVs) reliability to promote their commercialization. A physics-based observer that combines an Extended Kalman Filter (EKF) with a Sequential Probability Ratio Test (SPRT) has been employed to address two major failure modes in FCEV stacks: flooding and reduction of Electrochemical Active Surface Area (ECSA). Furthermore, the observer estimates the hidden states of a standard automotive airpath system to enable state-feedback control. Therefore, the proposed observer is a novel approach which holistically tackles three coupled problems (i.e., flooding, ECSA loss, and airpath state estimation) which are typically addressed individually. Additionally, the observer is computationally affordable and relies solely on typical vehicle sensors. The observer performance has been validated through simulations, testing various dynamic scenarios in the presence of flooding, ECSA loss failures, and sensors uncertainty. The estimation errors have been confined within a 3% error band for all test cases while the health indicators coherently responded in the presence of faults.

A one-dimensional model for Pt degradation and precipitation in proton exchange membrane fuel cell considering Pt nucleation, particle size growth, and band formation

Reducing Pt catalysts amount without sacrificing the performance and durability is critical for the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt degradation in the cathode catalyst layer (CCL) decreases the electrochemically active surface area (ECSA), and Pt precipitation, especially Pt band formation, has a significant effect on proton exchange membrane (PEM) stability, resulting in severe PEMFC degradation during long-term operation. In this study, a one-dimensional model is developed focusing on Pt catalyst degradation and precipitation, including Ostwald-ripening, mass loss, precipitation in the PEM from nucleation, particle size growth, to Pt band formation. The model accuracy is comprehensively validated against the corresponding experimental data, including ECSA loss and particle size distribution (PSD) evolution in the CCL under different operating conditions (temperature, relative humidity, and loading mode), as well as the precipitated Pt size distribution characteristics and local potential in the PEM. Using this model, the Pt band formation process is comprehensively analyzed, and the effects of operating conditions on Pt degradation and Pt band formation are investigated in detail. It is found that the nucleation stage is brief, and then the significant inhomogeneity at the size growth stage causes Pt band formation. In addition, the high activation enthalpy of dissolution under low humidity can effectively inhibit Pt degradation, and Ostwald-ripening is the mean cause of Pt degradation, which is likely to occur during the rapid voltage change period.

Effective photoelectrocatalysis of levofloxacin antibiotic with Ti/IrO2[sbnd]Nb2O5 in environmental samples

This work reports the development and application of a highly efficient catalyst based on IrO2 and Nb2O5 for the degradation of the antibiotic Levofloxacin (LFX) in simulated and real surface water samples. The IrO2Nb2O5 films, which were obtained by modified Pechini method, were deposited on a titanium substrate, leading to the production of Ti/IrO2Nb2O5 electrode. After being subjected to morphological, structural and electrochemical characterization, the Ti/IrO2Nb2O5 electrode was applied for the degradation of LFX using different processes, including electrolysis (EC) and photoelectrolysis (PhEC), and the results obtained were compared to that of UV–Vis irradiation-based photolysis. The application of the PhEC process led to a relatively higher and faster removal of LFX in the water matrices investigated, where 100% degradation rate and about 70% mineralization rate were obtained at the end of 1.5 h of treatment, compared to the individual photolysis and EC processes. The results obtained from quenching tests showed that LFX degradation under the PhEC process may be associated with the presence of active radicals, such as HO•, SO4•− and O2•−, in addition to the e−/h+ pair formed with the incidence of light during treatment. Apart from excellent photoelectrocatalytic activity and high stability, the Ti/IrO2Nb2O5 electrode exhibited high electrochemically active surface area (ECSA). The excellent results obtained from the application of the PhEC process in terms of TOC removal and the remarkable catalytic properties of Ti/IrO2Nb2O5 point to the high efficiency of the system proposed in this study when applied for the treatment and removal of organic pollutants from real water samples.

A 3D PtCo degradation model for long-term performance prediction of a scaled-up PEMFC under constant voltage operation

The non-uniform distribution of reactants, pressure, temperature and reaction rate in a scaled-up proton exchange membrane fuel cell (PEMFC) can lead to different catalyst degradation rate, impacting the long-term performance of PEMFCs. However, the local catalyst degradation behaviors in a PEMFC stack have not yet been fully understood due to the lack of experimental approaches and catalyst degradation model. In the present study, a numerical model is established for a 200 cm2 commercial-sized PEMFC stack with realistic anode and cathode flow fields. PtCo is employed as the cathode catalyst, and a 3D PtCo catalyst degradation model is developed to analyze the non-uniform evolution of the electrochemical active surface area (ECSA), current density, and Co2+ in the catalyst layers under the constant voltage conditions. The modeling results demonstrated that catalyst degradation is more severe downstream as well as under land of the cathode flow field, and the cathode catalyst layer (CCL) is the area most contaminated by the Co2+. The non-uniform catalyst degradation as well as Co2+ contamination increased the activation losses and local oxygen transport resistance. The catalyst degradation leads to a total power loss of 43.3 % after 80,000 h operation. The aging model provides a better understanding for large scale PEMFC stacks regarding its non-uniform PtCo degradation and can assist the future design of commercial PEMFCs with better lifetime.