CO Tolerance Research Articles

Enhanced CO Tolerance with PtRuAuPd/C Anode Catalyst in Proton Exchange Membrane Fuel Cells

Enhanced CO Tolerance with PtRuAuPd/C Anode Catalyst in Proton Exchange Membrane Fuel Cells

Advanced Ru/Ti4O7 catalyst for Tolerating CO and H2S poisoning to hydrogen oxidation reaction

CO and H2S poisoning of Pt-based catalysts for hydrogen oxidation reaction (HOR) stands as one of the long-standing hindrances to the widespread commercialization of proton exchange membrane fuel cells. In this paper, a Ru/Ti4O7 catalyst is successfully synthesized by the microwave-thermal method. This Ru/Ti4O7 catalyst shows a much higher noble metal mass activity than those of commercial PtRu/C and conventional Ru/C catalysts. The performance of the Ru/Ti4O7 catalyst under the exist of CO or H2S shows insignificant current decay, which is far superior to commercial PtRu/C and Pt/C catalysts. In this Ru/Ti4O7 catalyst, the electron transfer between Ru and Ti to form d-p orbital hybridization is considered to be responsible for the favorable catalytic HOR performance and the corresponding CO and H2S tolerance. The interaction mechanism formed by electron transfer may open a promising way for the subsequent development of anti-poisoning catalysts for PEM fuel cell hydrogen oxidation reaction.

Fabrication and performance investigation of high entropy perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 IT-SOFC cathode material

The high-entropy oxide (HEO) concept expands the design space of solid oxide fuel cell (SOFC) cathode materials. There is great potential for the development of HEO cathode materials that has not been fully explored, and the relationship between their chemical composition, grain size, and electrochemical performance is not yet fully understood. This experimental design involved the preparation of single-phase perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 HEO SOFC cathode materials, and we systematically studied the effects of synthesis temperature and microstructure on their electrochemical performance. The results show that as the synthesis temperature increases, structural transformations from multiphase to single-phase perovskite HEO can be observed. It exhibits excellent conductivity and electrochemical performance (the minimum polarization resistance reaches 0.033 Ω∙cm2, and the maximum power density is 664 mW∙cm−2). The single-phase perovskite HEO sample exhibits higher electrochemical performances compared to those of multiphase perovskite. Furthermore, it exhibits outstanding ability to suppress Sr segregation, chemical compatibility with Ce0.8Sm0.2O1.9(SDC), and CO2 tolerance performance. The Distribution of relaxation time(DRT) analysis shows that as the synthesis temperature (1000–1150 ℃) increase, HEO single-phase formed and the oxygen atom reduction ability of the SBBLP samples was improved; and the adsorption of gas oxygen on the electrode surface is limited with porosity decreases. The work shows it is interesting and valuable to optimize the performance of SOFC cathode materials using a high entropy design.

High ion exchange capacity perfluorosulfonic acid resine proton exchange membrane for high temperature applications in polymer electrolyte fuel cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have attract much attention from academic and industry, which can improve the catalyst activity, reduce Pt loading, enhance CO tolerance, and simplify water and heat management. High-temperature proton exchange membrane (HT-PEM) is the key component for HT-PEMFCs. Here, we provide an investigation of newly developed HT-PEM to evaluate its properties and performances in fuel cells above 90 °C. The HT-PEM exhibits an excellent proton conductivity of 136.1 mS cm−1 at 90 °C and 95% RH, and remarkable power density of 0.95 Wcm−2 at 105 °C and 80% RH. The stability and durability of HT-PEM are studied with varied testing methods. After the continuous operation at open circuit voltage (OCV) for 500 h and continuous dry-wet circulation for 20000 cycles at 90 °C, negligible change of OCV and hydrogen permeation current density are recorded, indicating good chemical and mechanical stability for HT-PEM. The improved property and performance originate from the new PFSA base material and improved morphology, in which the larger ionic clusters and continuous proton-transfer channels contribute to the superior performance, and the high glass transition temperature (Tg∼132 °C) induces good stability.

Ce-doping enhanced ORR kinetics and CO2 tolerance of Nd1-xCexBaCoFeO5+δ (x = 0–0.2) cathodes for solid oxide fuel cells

Addressing challenges in oxygen reduction efficiency and CO2 endurance is essential for advancing the electrochemical energy conversion performance of solid oxide fuel cells (SOFCs). This investigation introduces an innovative strategy by employing Ce doping to enhance the oxygen reduction kinetics and CO2 resistance of NdBaCoFeO5+δ (NBCF) cathodes. Ce doping effectively regulates the oxygen vacancy content, the ratio of Co3+/Co4+ and Fe3+/Fe4+ in NBCF, leading to substantial improvements in oxygen exchange, lattice diffusion, and charge transfer processes. Consequently, a significant enhancement in the oxygen reduction reaction catalytic activity and CO2 endurance is achieved. At 800 °C, the introduction of 10 mol% Ce doping results in a 65.3% reduction in Rp, reaching 0.024 Ω cm2. Simultaneously, the power density experiences a 50.8% enhancement, reaching 1.0 W cm−2. The current investigation presents a novel avenue towards the advancement of next-generation high-efficiency and stable cathode materials for SOFCs.

Density Functional Theory Study of Methanol Steam Reforming on Pt3Sn(111) and the Promotion Effect of a Surface Hydroxy Group

Methanol steam reforming (MSR) is studied on a Pt3Sn surface using the density functional theory (DFT). An MSR network is mapped out, including several reaction pathways. The main pathway proposed is CH3OH + OH → CH3O → CH2O → CH2O + OH → CH2OOH → CHOOH → COOH → COOH + OH → CO2 + H2O. The adsorption strengths of CH3OH, CH2O, CHOOH, H2O and CO2 are relatively weak, while other intermediates are strongly adsorbed on Pt3Sn(111). H2O decomposition to OH is the rate-determining step on Pt3Sn(111). The promotion effect of the OH group is remarkable on the conversions of CH3OH, CH2O and trans-COOH. In particular, the activation barriers of the O–H bond cleavage (e.g., CH3OH → CH3O and trans-COOH → CO2) decrease substantially by ~1 eV because of the involvement of OH. Compared with the case of MSR on Pt(111), the generation of OH from H2O decomposition is more competitive on Pt3Sn(111), and the presence of abundant OH facilitates the combination of CO with OH to generate COOH, which accounts for the improved CO tolerance of the PtSn alloy over pure Pt.

Enhancing the ORR kinetics and CO2 tolerance in PrBaCoCuO5+δ cathode for solid oxide fuel cells by bismuth doping

The sluggish kinetics of the oxygen reduction reaction (ORR) and susceptibility to CO2 poisoning present significant challenges in the application of intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, bismuth (Bi) was introduced as a dopant for the first time to enhance both the ORR activity and CO2 tolerance of PrBaCoCuO5+δ (PBCCO) cathode. Bi doping serves to concurrently modulate the oxygen vacancy content and carrier concentration. This dual regulation enhances the processes of oxygen adsorption, dissociation, and charge transfer, as evidenced by the distribution of relaxation time (DRT) technique. Furthermore, PBBCCO demonstrates exceptional CO2 tolerance and remarkable performance recovery following exposure to CO2-induced degradation. At 800 °C, the polarization resistance (Rp) and maximum power density (MPD) of PBBCCO were 0.026 Ω cm2 and 631 mW cm−2, respectively. Notably, Rp was reduced by 52.45%, and MPD exhibited an improvement of 45.11% at 800 °C. These findings highlight the significant impact of Bi doping on the performance of the PBCCO double perovskite cathode, underscoring its crucial importance for future developments of novel cathode materials.

Lithium doping enhanced ORR kinetics and CO2 tolerance of iron-based double perovskite cathode for solid oxide fuel cells

Fe-based double perovskites exhibit significant potential as cathode materials for solid oxide fuel cells (SOFCs) owing to their affordability, moderate thermal expansion, and impressive stability. Nevertheless, their practical utility has been constrained by their comparatively lower oxygen reduction reaction (ORR) catalytic activity. In this study, for the first time, lithium (Li) was employed as a dopant to improve the ORR activity of the Fe-based double perovskite PrBaFe2O5+δ (PBFO). The results indicated that the ratios of Fe3+/Fe2+ and Oads/Olat were effectively tuned by incorporating Li at Ba-sites of PBFO. Consequently, the adsorption and dissociation of oxygen, along with the charge transfer processes were regulated significantly, resulting in an increase in ORR kinetics and improved CO2 resistance. At 800 °C, PrBa0.9Li0.1Fe2O5+δ (PBLFO) demonstrated an Rp of 0.072 Ω cm², which was decreased by 43.3% compared to PBFO. Simultaneously, the maximum power density of PBLFO-based full cell was improved by 23.3%, reaching 670 mW cm−2. These findings suggest that Li-doping holds great potential for improving the performance of Fe-based SOFC cathodes, thereby contributing to the advancement of clean and sustainable energy technologies.

Low-Pt anodes with gradient molybdenum isomorphism for high performance and anti-CO poisoning PEMFCs

The development of low Pt-loading hydrogen oxidation reaction electrocatalysts with high catalytic activity, durability, and resistance to CO poisoning is essential for the commercialization of proton exchange membrane fuel cells. Herein, two hybrid catalysts coupled with single atoms are prepared. Electrochemical tests show that PtMo1/KB (Ketjen Black) (1.85 wt% Pt) exhibits extraordinary HOR activity and durability, with the mass activity in electrochemical cells and even PEMFCs are 8.36 and 2.71 times higher than that of commercial Pt/C, respectively. In addition, PtMo10/KB with novel configuration performed super high CO resistance (1000 ppm) in both three electrode and PEMFC measurement with an ultra-low Pt loading of 1.56 wt%, demonstrating the high application value in the next generation highly efficient PEMFC. DFT calculations also show that the adsorption energy of the intermediates H* and CO is optimized by tuning the d-band center of Pt, thus enhancing the HOR activity and CO tolerance of the catalyst. Meanwhile, in situ CO-adsorption surface-enhanced infrared adsorption spectroscopy also confirms that the weakening of the Pt-CO bond strength and the adsorption energy of CO contributes to the improvement of CO tolerance in PtMo10/KB.

Recent progress of antipoisoning catalytic materials for high temperature proton exchange membrane fuel cells doped with phosphoric acid

The current challenges and opportunities faced by HT-PEMFCs are discussed, as well as possible future solutions. This review can provide guidance for the future development of high-performance HT-PEMFC catalysts.

Revealing the role of a bridging oxygen in a carbon shell coated Ni interface for enhanced alkaline hydrogen oxidation reaction.

Encapsulating metal nanoparticles inside carbon layers is a promising approach to simultaneously improving the activity and stability of electrocatalysts. The role of carbon layer shells, however, is not fully understood. Herein, we report a study of boron doped carbon layers coated on nickel nanoparticles (Ni@BC), which were used as a model catalyst to understand the role of a bridging oxygen in a carbon shell coated Ni interface for the improvement of the hydrogen oxidation reaction (HOR) activity using an alkaline electrolyte. Combining experimental results and density functional theory (DFT) calculations, we find that the electronic structure of Ni can be precisely tailored by Ni-O-C and Ni-O-B coordinated environments, leading to a volcano type correlation between the binding ability of the OH* adsorbate and HOR activity. The obtained Ni@BC with a optimized d-band center displays a remarkable HOR performance with a mass activity of 34.91 mA mgNi-1, as well as superior stability and CO tolerance. The findings reported in this work not only highlight the role of the OH* binding strength in alkaline HOR but also provide guidelines for the rational design of advanced carbon layers used to coat metal electrocatalysts.

A unique one-pot strategy for PdH0.706 nanoparticles with enhanced stability and activity towards the ethanol oxidation reaction.

We present a novel and universal solvothermal method for fabricating high-hydrogen-content PdH0.706 nanoparticles, which demonstrate 1.53 A mg-1 ethanol oxidation activity, 1.39 and 1.76 times higher than hydrogen-free Pd and commercial Pd black, respectively, along with superior stability and CO tolerance under alkaline conditions.

Uleashing efficient and CO-resilient alkaline hydrogen oxidation of Pd3P through phosphorus vacancy defect engineering

A high-performance and highly CO-resilient hydrogen oxidation reaction (HOR) electrocatalyst is heralded as core material to solve the commercial deployment of hydrogen fuel cells. Phosphorus vacancies, as a type of delicate point defect, could effectively and flexibly modulate the catalytic performance. Therefore, based on the vacancy design philosophy of “less is more”, we synthesize a phosphorus-vacancy-rich Pd3P@C (Vp-Pd3P@C) catalyst with bowl-like hemisphere structure for alkaline HOR, for the first time. The Vp-Pd3P@C catalyst exhibits remarkable mass activity and exchange current density of 1.66 mA μgPd–1 and 3.2 mA cm<font style=’color:red’>–2, respectively, surpassing those of Pd3P@C (0.45 mA μgPd–1, 1.78 mA cm<font style=’color:red’>–2) and commercial Pt/C (0.3 mA μgPt–1, 2.29 mA cm<font style=’color:red’>–2). Intriguingly, the catalyst can tolerate 1000 ppm CO that Pt/C catalyst lacks. Density functional theory calculations uncover that the optimal local coordination environment and favorable electronic structure that rooted from phosphorus vacancy enable optimum adsorption kinetics of hydrogen and hydroxyl while concomitantly suppressing Pd 4d → CO 2π* back donation, contributing to the remarkable HOR reactivity and CO tolerance.

An excellent bismuth-doped perovskite cathode with high activity and CO2 resistance for solid-oxide fuel cells operating below 700 °C

Lowering the operating temperatures of solid-oxide fuel cells (SOFCs) is critical, although achieving success in this endeavor has proven challenging. Herein, Bi0.15Sr0.85Co0.8Fe0.2O3−δ (BiSCF) is systematically evaluated as a carbon dioxide (CO2)-tolerant and highly active cathode for SOFCs. BiSCF, which features Bi3+ with an ionic radius similar to Ba2+, exhibits activity (e.g., 0.062 Ω cm2 at 700 °C) comparable to that of Ba0.5Sr0.5Co0.8Fe0.2O3−δ and PrBaCo2O5+δ, while demonstrating a considerable advantage over Bi-doped cathodes. Moreover, BiSCF exhibits long-term stability over a period of 500 h, and an anode-supported cell with BiSCF achieves a power density of 912 mW cm−2 at 650 °C. The CO2-poisoned BiSCF exhibits quick reversibility or slight activation after returning to normal conditions. The exceptional CO2 tolerance of BiSCF can be attributed to its reduced basicity and high electronegativity, which effectively restrict surface Sr diffusion and hinder subsequent carbonate formation. These findings highlight the substantial potential of BiSCF for SOFCs operating below 700 °C.

Enhanced performance of proton exchange membrane fuel cells by Pt/carbon/antimony-doped tin dioxide triple-junction catalyst

A composite material comprising carbon black and Sb-doped SnO2 (ATO) is employed as a support for a Pt catalyst in a membrane electrode assembly (MEA) to improve the performance of a proton-exchange membrane fuel cell under low-humidity conditions. The effects of Sb-doping on the crystal, structural, and electrochemical characteristics of ATO particles are being examined. In a single cell test, the ratio of Sb in ATO is systematically optimized to improve performance. The distribution of Pt nanoparticles is uniform on carbon black and ATO carrier, forming notable triple-junction points at the interface of carbon black and ATO carrier. This structure thus induces a strong interaction between Pt and ATO, promoting the content of metallic Pt. Compared with a Pt/C catalyst, the best-performing Pt/C–ATO catalyst exhibits superior electrochemical activity, stability, and CO tolerance. The power density of MEA with the Pt/C–ATO catalyst is 15% higher than that of the MEA with the Pt/C catalyst

Enhancing Direct Methanol Oxidation with Pt-Pd Alloy Nanoparticles Synthesized By Gas Diffusion Electrocrystallization (GDEx)

Direct methanol fuel cells (DMFCs) are a promising sustainable energy solution due to their high energy density, low-temperature operation, and portability. However, sluggish methanol oxidation reaction (MOR) kinetics hinders their successful commercialization.1,2 Pt is a highly active MOR catalyst due to its ability to adsorb and decompose methanol on its surface. However, when pure Pt is used, the adsorption of oxidation intermediaries, i.e., CO, occurs, blocking catalytically-active sites and reducing the catalytic efficiency.2 A promising strategy to improve the catalytic activity and CO tolerance of Pt is by alloying. Among several candidates, Pd stands out due to its identical crystal structure and similar lattice constant to Pt, resulting in single-phase bimetallic materials with strong coupling and improved catalytic performance. In addition, the active surface area is enhanced, and stability is improved by using Pt-Pd alloys.3 We recently reported an electrochemical method for synthesizing platinum group (PGMs, i.e., Pt, Pd, Rh) nanoparticles (NPs) using Gas-Diffusion Electrocrystallization, best known as the GDEx process.4 In GDEx, CO2 and water are reduced using a gas diffusion electrode, producing CO and H2, which in turn reduce PGMs ions in solution, forming metal nanoclusters of 10 nm–40 nm composed of even smaller nanocrystals of 2 nm–4 nm. In this work, we used GDEx to synthesize Pt-Pd alloy NPs with different metal ratios (Pt100, Pt75-Pd25, Pt50-Pd50, Pt25-Pd75 and Pd100). The Pt-Pd alloy NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy. The size distribution of the synthesized nanomaterials was between 15 nm–30 nm, increasing in size with increasing Pd content. The catalytic activity of the Pt-Pd alloy NPs toward methanol oxidation was measured in 0.1 M HClO4. The electrochemical surface area (ECSA), measured by the Cu underpotential deposition method,5 was 37.1 ± 2.1, 36.1 ± 2.7, 42.5 ± 1.7 and 56.1 ± 2.9 m2 gPt -1 for Pt100, Pt75-Pd25, Pt50-Pd50, and Pt25-Pd75 respectively. The mass activity (MA, fig.1a), defined by the current density per unit mass of Pt loading at the forward peak, was 452 ± 10, 345 ± 16, 365 ± 21 and 189 ± 15 for Pt100, Pt75-Pd25, Pt50-Pd50, Pt25-Pd75. Even though the MA for Pt75-Pd25 and Pt50-Pd50 was lower than for Pt100, their onset potential was smaller (0.503 VRHE for Pt75-Pd25 and 0.488 VRHE for Pt50-Pd50) than for Pt100 (0.530 VRHE) indicating that the MOR is more favourable on those alloys. Besides, during the accelerated stability test (ADT, Fig.1b), after 1000 cycles, Pt75-Pd25 and Pt50-Pd50 showed higher stability and resistance towards CO poisoning than Pt100 by holding 80% and 70% of their peak current density. In comparison, Pt100 only kept ∼60% of its peak current density under the same conditions.In summary, the GDEx process allows the synthesis of Pt-Pd alloy NPs with a similar or superior catalytic performance towards MOR than pure Pt NPs, i.e., similar MA but with a better tolerance towards CO poisoning. The selectivity of the GDEx process for PGMs allows the synthesis of Pt-Pd catalysts for DMFCs not only from synthetic solutions but also from complex matrixes that contains a mixture of both PGMs (i.e., leachates from spent automotive catalytic converters).This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreements No. 958302 (PEACOC project) and No. 101091715 (FIREFLY project). Yuda A, Ashok A, Kumar A. Catalysis Reviews. 2022;64(1):126-228.Ren X, Lv Q, Liu L, Liu B, Wang Y, Liu A, Wu G. Sustain. Energy Fuels. 2020;4(1):15-30.Yousaf AB, Imran M, Uwitonze N, Zeb A, et al. J . Phy s. Chem . C. 2017;121(4):2069-79.Martinez-Mora O, Pozo G, Leon-Fernandez LF, Fransar J, Dominguez-Benetton X., RSC Sustain. 2023; DOI: 10.1039/D3SU00046J.Green CL, Kucernak A. J. Phys. Chem. B. 2002;106(5):1036-47. Figure 1

The Trade-Off Relationship between Particle Proximity Effect and Low-Pt Loading to Optimize Oxygen Reduction and Methanol Oxidation Reaction Activity

Pt-based electrocatalysts have long been considered as the most effective oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) catalysts due to their excellent intrinsic activity. For supported catalysts, Pt loading, particle size, interparticle distance (ipd), and interaction with support are identified as key contributors for high activity and selectivity. The proximity effect is a relatively new topic in catalysis research. There is a contradiction between the traditional view which induces the electronic interaction to reduce the activity and the new view which causes the electrical double-layer overlap of adjacent nanoclusters, changes the potential distribution and improves the specific activity. [1, 2]To this end, we have developed the nitrogen-doped graphite-like carbon sheets supporting low-Pt loading (Pt@N-GC) with uniform sizes and controllable ipd, and disentangled the main effect of ipd on ORR activity/selectivity and MOR activity/CO tolerance. Combining electrochemical tests and the trade-off mechanism between proximity effect and low-Pt loading, the following trends were obtained:1) 10.0 wt% Pt@N-GC with highest Pt loading and lowest ipd inhibits 2e- ORR by strong adsorption and reabsorption of *OOH due to the presence of closer Pt sites, and improves 4e- ORR selectivity. However, the mass activity/specific activity reached the maximum under the optimal low-Pt loading of 5.0 wt%.2) Similarly, 10.0 wt% Pt@N-GC weakened the adsorption of the -OH group of oxidized COads intermediates, led to the strong adsorption of COads on the catalyst surface, inactivated of Pt sites and reduced the CO resistance. Considering the need to improve CO tolerance while increasing MOR activity, the 5.0 wt% low-Pt loading catalyst exhibiting the best MOR performance under the optimal ipd.3) Benefiting by the synergistic effect of Pt nanoparticles and N-GC support, all Pt@N-GCs exhibit bifunctional electrocatalytic activity and durability.We attribute these findings to the underlying mechanism trade-off between the particle proximity effect and low-Pt loading under the uniform particle size and controlled ipd (Figure. 1). We believe the proximity effect has positive and negative effects, how to maximize the advantages of proximity effect can provide valuable guidance for the design and optimization of low-Pt loading bifunctional electrocatalysts in the future.[1] M. Nesselberger, M. Roefzaad, R.F. Hamou, P.U. Biedermann, F.F. Schweinberger, S. Kunz, K. Schloegl, G.K. Wiberg, S. Ashton, U. Heiz, K.J. Mayrhofer, M. Arenz, Nat. Mater., 12 (2013) 919-924.[2] M. Watanabe, H. Sei, P. Stonehart, J. Eelectroanal. Chem., 261 (1989) 375-387. Figure 1. The trade-off mechanism analysis between proximity effect and low-Pt loading. Figure 1

Regeneration Strategies for Ruthenium-Poisoned ORR Catalysts in Reformate PEM Fuel Cells

Reformate polymer electrolyte membrane (PEM) fuel cells have great potential to transform the global maritime transportation in a more environmentally friendly and CO2-neutral manner. Platinum (Pt)-ruthenium (Ru) alloy nanoparticles (NPs) supported on carbon (PtRu/C) are the most commonly used electrocatalyst material to accelerate the hydrogen oxidation reaction (HOR) of the reformate gas (H2/CO2/CO) at the anode [1]. The high CO tolerance of PtRu/C catalysts is based on the ensemble effect [2]. However, these materials suffer extremely from the Ru dissolution and Ruz+ crossover to the cathode, which are the main degradation processes in reformate PEM fuel cells. At the cathode, the Ruz+ species immediately redeposit on the Pt/C catalyst, resulting in a drastic decay of the entire performance of the reformate PEM fuel cell. Even if the Ru coverage on the Pt/C catalyst is less than 20 at. %, there is an 8-fold decrease in kinetics of the oxygen reduction reaction (ORR) [3]. Therefore, it is necessary to develop a regeneration protocols to mitigate the Ru poisoning at the cathode.In this study, we developed and tested different regeneration protocols to recover the Ru-poisoned ORR catalysts using a rotating disc electrode (RDE) set-up. To simulate the worst situation for poisoned ORR catalysts, commercially available Pt-Ru alloy NPs supported on carbon were used and characterized by TEM, XRD, XAS, and XPS. In general, our regeneration protocols can be classified into dynamic and steady-state conditions. All protocols included a pre-activation step by holding the potential at 1.4 VRHE for 5 minutes in 0.1 M HClO4. During the dynamic regeneration process, the potential was switched between 1.4 VRHE and 1.6 VRHE with a duration time of 10 s by 10 times using a pulse voltammetry technique. In contrast, the steady-state regeneration protocol consisted of only one pulse at 1.6 VRHE for 100 s. For the recovery procedure of the poisoned ORR catalysts, the experimental parameters were correlated with the changes in ORR performance and electrochemically active surface area (ECSA) via CO stripping as well as the loss of Ru content and particle structure established from μ-XRF, ICP-OES, and TEM.After the dynamic regeneration process, the ORR mass activity (MA) and specific activity (SA) of PtRu2/Vulcan increase initially from 0.07 ± 0.01 to 0.21 ± 0.02 A mgPt+Ru -1 and 62 ± 9 to 190 ± 16 μA cmPt+Ru -2 at 0.85 VRHE, iR-free, respectively. Hence, the dynamic regeneration protocol leads to an improvement of the MA by a factor of 2 and of the SA by 2.1 for PtRu2/Vulcan. In comparison, the steady-state regeneration experiment shows an enhancement by 2.2 (0.26 ± 0.03 A mgPt+Ru -1) for MA and by 3.5 (276 ± 16 μA cmPt+Ru -2) for SA, respectively. Therefore, the steady-state regeneration process is more effective compared to the dynamic regeneration protocol. Based on the µ-XRF data, we observed that the Ru content of the PtRu2/Vulcan decreases from 62 ± 2 at. % to either 5 ± 1 at. % or 8 ± 1 at. % after the steady-state or dynamic regeneration process. The loss of Ru from the particle surface can also be monitored by CO stripping, where the CO oxidation peak is shifted positively from 0.58 VRHE to 0.67 VRHE and 0.63 VRHE after steady-state and dynamic regeneration protocol, respectively. As the particle size of the PtRu2 NPs is around ~ 5.3 ± 1.2 nm, the ECSA is mainly unchanged after both regeneration protocols.Based on our results, the steady-state regeneration process with 1.6 VRHE for 100 s is more effective than the dynamic one with pulses from 1.4 to 1.6 VRHE each with 10 s by 10 times to recover the ORR activity of the PtRu2 alloy NPs. The proposed regeneration protocols can improve the performance and life-time of the reformate PEM fuel cell.

Mixed-Dimensional Partial Dealloyed PtCuBi/C as High-Performance Electrocatalysts for Methanol Oxidation with Enhanced CO Tolerance.

Developing efficient electrocatalysts for methanol oxidation reaction (MOR) is crucial in advancing the commercialization of direct methanol fuel cells (DMFCs). Herein, carbon-supported 0D/2D PtCuBi/C (0D/2D PtCuBi/C) catalysts are fabricated through a solvothermal method, followed by a partial electrochemical dealloying process to form a novel mixed-dimensional electrochemically dealloyed PtCuBi/C (0D/2D D-PtCuBi/C) catalysts. Benefiting from distinctive mixed-dimensional structure and composition, the as-obtained 0D/2D D-PtCuBi/C catalysts possess abundant accessible active sites. The introduction of Cu as a water-activating element weakens the COads, and oxophilic metal Bi facilitates the OHads, thereby enhancing its tolerance to CO poisoning and promoting MOR activity. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS) collectively reveal the electron transfer from Cu and Bi to Pt, the electron-enrichment effect induced by dealloying, and the strong interactions among Pt-M (Cu, Pt, and Bi) multi-active sites, which improve the tuning of the electronic structure and enhancement of electron transfer ability. Impressively, the optimized 0D/2D D-PtCuBi/C catalysts exhibit the superior mass activity (MA) of 17.68 A mgPt -1 for MOR, which is 14.86 times higher than that of commercial Pt/C. This study offers a proposed strategy for Pt-based alloy catalysts, enabling their use as efficient anodic materials in fuel cell applications.

Enhancing ORR activity and CO2 tolerance of Pr0.4Sr0.6Co0.2Fe0.8O3-δ-based SOFC cathode through synergistic doping and surface modification

The development of cathodes with high catalytic activity and stability remains a critical challenge for the commercialization of solid oxide fuel cells (SOFCs). In this study, a novel approach combining doping and surface modification was employed to enhance the catalytic activity and CO2 resistance of Pr0.4Sr0.6Co0.2Fe0.8O3-δ (PSCF) cathode. Initially, Ni was partially substituted for Fe in PSCF, resulting in the reduction of the average bond energy of metal–oxygen, thereby increasing oxygen vacancy concentration and electrochemical activity. The polarization resistance of PSCFN0.1 at 800 °C was found to be 0.025 Ω·cm2, representing a 32.4 % reduction compared to PSCF. Subsequently, Pr(NO3)3 solution was impregnated on the surface of the PSCFN0.1 using a spin-coating technique, resulting in the formation of a PrO2/PSCFN0.1 heterostructure that significantly improved the oxygen reduction reaction (ORR) kinetics. At 800 °C, the polarization resistance of PrO2-PSCFN0.1 was only 0.016 Ω·cm2, a 56.8 % reduction compared to PSCF. Moreover, the peak power density of PrO2-PSCFN0.1 reached 1190 mW·cm−2 at 800 °C, representing a substantial increase of 207.4 % compared to PSCF. Furthermore, PrO2-PSCFN0.1-based full cell exhibited excellent performance stability and CO2 resistance. This work provides an effective strategy to explore novel cathodes for SOFCs.