High CO Tolerance Research Articles

Large-Scalable CO-Tolerant Ultrathin PtTe2 Nanosheets for Formic Acid Oxidation.

Developing large-scale platinum (Pt) alloys that simultaneously exhibit high formic acid oxidation reaction (FAOR) activity and robust CO tolerance remains a significant challenge for practical fuel cell applications. Here, a facile and universal in situ synthesis approach is presented to create ultrathin platinum-tellurium nanosheets on carbon support (PtTe2 NSs/C), which enables high CO tolerance and FAOR activity while achieving the massive production of PtTe2 NSs/C. Specifically, the 10-gram-scale PtTe2 NSs/C achieves exceptional specific activity and mass activity of 14.3mA cm-2 and 3.6 A mgPt -1, respectively, which are 52.9 and 22.5 times greater than those of commercial Pt/C. Moreover, the 10-gram-scale PtTe2 NS/C exhibits significantly higher FAOR stability than pristine Pt NSs/C and commercial Pt/C. Detailed mechanism and computational investigations collectively reveal that the integration of Te into Pt lattices enhances the utilization of Pt while constructing high-density unsaturated "Pt-Te sites" on the surface of PtTe2 NSs/C, conferring high CO tolerance to PtTe2 NSs/C and thus substantially enhancing the FAOR activity. This work contributes to providing a universal method for scaling up next-generation high-performing FAOR catalysts.

Rare-earth oxide promoted Pd electrocatalyst for formic acid oxidation.

The development of Pd-based materials with high activity and long-term stability is crucial for their practical applications as an anode catalyst in direct formic acid fuel cells. Herein, we reveal that the catalytic activity of Pd towards formic acid oxidation can be enhanced by incorporation of a series of rare-earth oxides, including Sc2O3, CeO2, La2O3, and Pr2O3. For example, Pd nanoparticles incorporated with Sc2O3 supported on nitrogen-doped reduced graphene oxide (Pd-Sc2O3/N-rGO-x, x = 1/3, 1/2, 2/3, 1, and 3/2; "x" denotes the molar ratio of Pd : Sc) can be obtained using a sodium borohydride reduction method. When directly used as an electrocatalyst towards formic acid oxidation (FAO), Pd-Sc2O3/N-rGO-2/3 exhibits the highest mass current density of 972.9 mA mgPd-1, surpassing that of the reference catalysts Pd/C (262.6 mA mgPd-1) and Pd/N-rGO (304.9 mA mgPd-1). More importantly, the Pd-Sc2O3/N-rGO-2/3 catalyst demonstrates high CO tolerance and long-term stability in the FAO reaction. The improved electrooxidation activity and stability could be attributed to the synergistic effect between Sc2O3 and Pd nanoparticles. Therefore, this study presents a crucial contribution to the advancement of various rare-earth oxides in enhancing Pd activity towards FAO and beyond.

Electrocatalyst Design for Carbon Dioxide Co-Reduction with Nitrate for Sustainable Synthesis of Urea

The electrochemical co-reduction of nitrate (NO3 -) and carbon dioxide (CO2) for the synthesis of urea has drawn much research focus recently because it creates value-added products from environmentally hazardous pollutants. Urea is the major ingredient of fertilizer, that is currently produced through the Bosch-Meiser process starting from ammonia (NH3) and carbon dioxide (CO2), in which ammonia is produced through the Haber-Bosch process, leading to significantly high energy consumption and CO2 emissions. Urea electrosynthesis is a complex 16e-, 12H+ transfer reaction with multiple possible by-products such as H2, CO, HCOOH, NO2 -, NH3, etc., making the electrocatalyst design toward urea selectivity a big challenge.To reliably quantify the urea produced, we present an updated method for urea quantification using the diacetylmonoxime-thiosemicarbazide (DAMO-TSC) method while excluding the interference of NO2 - by-product. We believe this method can guide the electrocatalysis community to establish an updated protocol and avoid false positive/overestimating results.We will then present a catalyst designed for urea electrosynthesis consisting of Pd nanoparticles in nanoscale proximity to atomically dispersed Fe-Nx sites on a carbon matrix (FeNC). Our group has previously presented Pd nanoparticles and FeNC materials as efficient catalysts for CO2 and NO3 - reduction respectively. Their association at the nanoscale demonstrates over 20% urea faradaic efficiency at -0.5 V (vs RHE) with 100% N-selectivity (All by-products contain nitrogen). These very promising results provide us with the baseline to elucidate the role of individual active sites on the C-N coupling mechanism. To this effect, reaction intermediates of CO2 and NO3 - co-reduction are investigated by in-situ vibrational spectroscopy (Raman, infrared). This study validates the approach of tuning electrocatalysts through mechanistic studies realizing CO2 / NO3 - co-reduction.Reference: Murphy, E., Liu, Y., Matanovic, I., Rüscher, M., Huang, Y., Ly, A., Guo, S., Zang, W., Yan, X., Martini, A., Timoshenko, J., Cuenya, B. R., Zenyuk, I. V., Pan, X., Spoerke, E. D., & Atanassov, P. Elucidating electrochemical nitrate and nitrite reduction over atomically-dispersed transition metal sites. Nat Commun 14, 4554 (2023).Guo, S., Liu, Y., Murphy, E., Ly, A., Xu, M., Matanović, I., Pan, X., & Atanassov, P. Robust palladium hydride catalyst for electrocatalytic formate formation with high CO tolerance. Applied Catalysis. B, Environmental, 316, 121659. (2022).Huang, Y., Wang, Y., Liu, Y., Ma, A., Gui, J., Zhang, C., Yu, Y., & Zhang, B. Unveiling the quantification minefield in electrocatalytic urea synthesis. Chemical Engineering Journal, 453, 139836. (2023).

Single Cell Regeneration Investigations on Ruthenium Poisoned Cathode Electrocatalysts for PEMFC

PEMFCs operating with reformate gases (a mixture of H2, CO2, and CO) are a promising alternative for CO2-neutral and environmentally friendly maritime transportation. [1] However, even trace amounts of CO in the hydrogen feed rapidly deactivate the platinum (Pt) electrocatalysts, leading to a high anode overpotential. [2] Pt-ruthenium (Ru) alloy nanoparticles (NPs) supported on carbon (PtRu/C) are among the most widely used anode electrocatalyst materials due to their high CO tolerance during the hydrogen oxidation reaction (HOR). [2, 3] Nevertheless, the PtRu/C anode catalysts suffer from the Ruz+ dissolution followed by crossover through the membrane and re-deposition onto the Pt/C cathode catalyst surface during the long-time PEMFC operation. [3] These phenomena are the main degradation processes in PEMFCs operated with reformate gas. Even at a Ru coverage of the Pt/C cathode catalyst surface of less than 20 %, there is an 8-fold decrease in the kinetics of the oxygen reduction reaction (ORR). [4, 5] Hence, the development of electrochemical regeneration procedures to mitigate or remove Ru-poisoning of the cathode catalyst surface on cell level is essential to extend the lifetime of PEMFCs, e.g. for maritime applications. [6]Based on our previous work in a three-electrode setup [6], we transferred a selective set of regeneration protocols for Ru-poisoned ORR catalysts using a fully automatic single-cell PEMFC test station. Therefore, catalyst coated membranes (CCMs) with a 12 cm2 geometric surface area were prepared by using two commercial Pt-Ru/C catalysts with different atomic ratios on the cathode side, maintaining the Pt loading of 0.2 - 0.3 mgPt cm-2 geo, while the anode electrode layer contained Pt/C with around 0.1 mgPt cm-2 geo. The anode side was exposed to successive H2/air fronts with different residence times as part of a regeneration strategy of the cathode electrode. The effect of the H2/air front and their residence time were investigated through electrochemical characterization methods, such as polarization curves, Tafel slope, ECSA, HFR, and impedance spectroscopy. Electrochemical performance results were correlated with PEMFC operating conditions (H2/air front, residence times) and structural data to evaluate changes in particle size, structure, and chemical composition of two different Pt-Ru/C catalysts using several techniques like cross-section scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and microscopic X-ray fluorescence spectroscopy (µ-XRF).Our work evaluated different electrochemical recovery protocols of Ru-poisoned ORR catalyst materials to identify the most promising set of parameters for their re-activation procedure and therefore improve the lifetime of PEMFCs.

Rationally Designed L12-Pt2RhFe Intermetallic Catalyst with High CO-Tolerance for Alkaline Methanol Electrooxidation.

It is a grand challenge to deep understanding of and precise control over functional sites for the rational design of highly efficient catalysts for methanol electrooxidation. Here, an L12-Pt2RhFe intermetallic catalyst with integrated functional components is demonstrated, which exhibits exceptional CO tolerance. The Pt2RhFe/C achieves a superior mass activity of 6.43 A mgPt -1, which is 2.23-fold and 3.53-fold higher than those of PtRu/C and Pt/C. Impressively, the Pt2RhFe/C exhibits a significant enhancement in durability owing to its high CO-tolerance and stability. Density functional theory calculations reveal that high performance of Pt2RhFe intermetallic catalyst arises from the synergistic effect: the strong OH binding energy (OHBE) at Fe sites induce stably adsorbed OH species and thus facilitate the dehydrogenation step of methanol via rapid hydrogen transfer, while moderate OHBE at Rh sites promote the formation of the transition state (Pt-CO···OH-Rh) with a low activation barrier for CO removal. This work provides new insights into the role of OH binding strength in the removal of CO species, which is beneficial for the rational design of highly efficient catalysts.

Pt Nanoparticles on Multi-Walled Carbon Nanotubes with High CO Tolerance for Methanol Electrooxidation.

Anode catalysts are important for direct methanol fuel cells (DMFCs) of energy conversion. Herein, we report a novel strategy by ethylene glycol-based deep eutectic solvents (EG-DESs) for the fabrication of a multi-walled carbon nanotubes (MWCNTs)-supported Pt nanoparticles catalyst (referred to as Pt/CNTs-EG-DES). The Pt/CNTs-EG-DES catalyst provides an increased electrochemically active surface area (ECSA) and shows remarkably improved electrocatalytic performance towards methanol oxidation reaction compared to Pt/CNTs-W (fabricated in water) and commercial Pt/C catalysts. The improved performance is attributed to the generation of more Pt-O bonds which change the electronic states of the Pt atoms and the special node structure that obtains more active sites for a high CO resistance. This study suggests an effective synthesis strategy for Pt-based electrocatalysts with high performance for DMFC applications.

Mo-modified Pt/C electrocatalyst prepared by the catalytic decomposition of molybdenum peroxo-complexes for the hydrogen oxidation reaction with enhanced CO tolerance

Commercial 20 % Pt/C catalyst was modified by molybdenum via catalytic decomposition of peroxocomplexes of molybdenum with the subsequent reduction of the Pt2Mo1/C precursor in H2 flow at 600 °C. The detailed HRTEM, EDX, XRD and XPS studies showed that amorphous molybdenum oxide was deposited on Pt particles surface and partially on carbon support. After reduction of the Pt2Mo1/C precursor, the substantial Mo fraction merges the structure of Pt particles thus forming PtMo alloy with reduced lattice parameter, while the rest of molybdenum covers the surface of PtMo particles as MoO3. The presented method of Mo-modification of Pt-based catalysts provides rather simple way to vary Pt:Mo molar ratio. Electrochemical study revealed that the amount of the surface MoO3 plays a key role in the CO tolerance of the PtMo/C catalyst. As prepared Pt2Mo1/C precursor is 15 times superior to the Pt/C catalyst in the CO-tolerance. After reduction, the Pt2Mo1/C electrocatalyst exhibits extremely high CO-tolerance, more than 100 times higher than that of the pristine commercial platinum catalyst.

Halogen Tailoring of Platinum Electrocatalyst with High CO Tolerance for Methanol Oxidation Reaction.

The catalytic activity of platinum for CO oxidation depends on the interaction of electron donation and back-donation at the platinum center. Here we demonstrate that the platinum bromine nanoparticles with electron-rich properties on bromine bonded with sp-C in graphdiyne (PtBr NPs/Br-GDY), which is formed by bromine ligand and constitutes an electrocatalyst with a high CO-resistant for methanol oxidation reaction (MOR). The catalyst showed peak mass activity for MOR as high as 10.4 A mgPt -1, which is 20.8 times higher than the 20 % Pt/C. The catalyst also showed robust long-term stability with slight current density decay after 100 hours at 35 mA cm-2. Structural characterization, experimental, and theoretical studies show that the electron donation from bromine makes the surface of platinum catalysts highly electron-rich, and can strengthen the adsorption of CO as well as enhance π back-donation of Pt to weaken the C-O bond to facilitate CO electrooxidation and enhance catalytic performance during MOR. The results highlight the importance of electron-rich structure among active sites in Pt-halogen catalysts and provide detailed insights into the new mechanism of CO electrooxidation to overcome CO poisoning at the Pt center on an orbital level.

Strengthening the activity and CO tolerance with bi-component PtNi/NbN-C catalyst for methanol alkaline electrooxidation

It is critical to create the anodic catalysts with high efficiency and economy for direct methanol fuel cells (DMFCs). Here, a series of PtNi/NbN-C catalysts (M=Co, Sn, Ni) are developed using the glycol solvothermal process, to investigate the catalytic effficiency for alkaline methanol oxidation reaction (MOR). Catalytic performance evaluation experiments show that the doped Ni species bring the enhancement effect on Pt/NbN-C for the alkaline MOR. The mass activities of PtxNiy/NbN-C show a volcanic trend with the increased Ni contents. PtNi/NbN-C has the highest mass activity (6025.5 mA·mg-1Pt) for alkaline MOR, 18.3 times greater than that of the Pt/C commercial catalyst. The LSV, EIS, Tafel, CA and CO stripping results imply PtNi/NbN-C also exhibits the lowest onset potential, charge transfer resistance, fastest kinetics, highest CO tolerance and stability. When the XRD, HRTEM, and XPS analysis are combined, it is discovered that the electronic effect between the Pt, Ni, and NbN species is mostly responsible for the catalytic performance enhancement is mainly depend on the electronic effect among the Pt, Ni and NbN species. The presence of Pt in an electron-deficient state can enhance the conversion of adsorbed methanol and intermediates, evidenced by a direct relationship between the d-band centers and the mass activities for MOR of different catalysts. This study may provide guidance for the development of anodic materials for DMFCs.

Electronegativity- induced cobalt-doped platinum hollow nanospheres with high CO tolerance for efficient methanol oxidation reaction

Although Platinum (Pt)-based alloys have garnered significant interest within the realm of direct methanol fuel cells (DMFCs), there still exists a notable dearth in the exploration of the catalytic behavior of the liquid fuels on well-defined active sites and unavoidable Pt poisoning because of the adsorbed CO species (COads). Here, we propose an electronegativity-induced electronic redistribution strategy to optimize the adsorption of crucial intermediates for the methanol oxidation reaction (MOR) by introducing the Co element to form the PtCo alloys. The optimal PtCo hollow nanospheres (HNSs) exhibit excellent high-quality activity of 3.27 A mgPt−1, which is 11.6 times and 13.1 times higher than that of Pt/C and pure Pt, respectively. The in-situ Fourier transform infrared reflection spectroscopy validates that electron redistribution could weak CO adsorption, and subsequently decrease the CO poisoning adjacent the Pt active sites. Theoretical simulations result show that the introduction of Co optimize surface electronic structure and reduce the d-band center of Pt, thus optimized the adsorption behavior of COads. This study not only employs a straightforward method for the preparation of Pt-based alloys but also delineates a pathway toward designing advanced active sites for MOR via electronegativity-induced electronic redistribution.

Unconventional hcp/fcc Nickel Heteronanocrystal with Asymmetric Convex Sites Boosts Hydrogen Oxidation.

Developing non-platinum group metal catalysts for the sluggish hydrogen oxidation reaction (HOR) is critical for alkaline fuel cells. To date, Ni-based materials are the most promising candidates but still suffer from insufficient performance. Herein, we report an unconventional hcp/fcc Ni (u-hcp/fcc Ni) heteronanocrystal with multiple epitaxial hcp/fcc heterointerfaces and coherent twin boundaries, generating rugged surfaces with plenty of asymmetric convex sites. Systematic analyses discover that such convex sites enable the adsorption of *H in unusual bridge positions with weakened binding energy, circumventing the over-strong *H adsorption on traditional hollow positions, and simultaneously stabilizing interfacial *H2O. It thus synergistically optimizes the HOR thermodynamic process as well as reduces the kinetic barrier of the rate-determining Volmer step. Consequently, the developed u-hcp/fcc Ni exhibits the top-rank alkaline HOR activity with a mass activity of 40.6 mA mgNi -1 (6.3 times higher than fcc Ni control) together with superior stability and high CO-tolerance. These results provide a paradigm for designing high-performance catalysts by shifting the adsorption state of intermediates through configuring surface sites.

PtPdAg nanotrees with low Pt content for high CO tolerance within formic acid and methanol electrooxidation

PtPdAg nanotrees with low Pt content for high CO tolerance within formic acid and methanol electrooxidation

Halogen Tailoring of Platinum Electrocatalyst with High CO Tolerance for Methanol Oxidation Reaction

The catalytic activity of platinum for the CO oxidation depends on the interaction of electron donation and back‐donation at the platinum center. Here we demonstrate that the platinum bromine nanoparticles with electron‐rich properties on bromine bonded with sp‐C in graphdiyne (PtBr NPs/Br‐GDY), which is formed by bromine ligand and constitutes an electrocatalyst with a high CO‐resistant for methanol oxidation reaction (MOR). The catalyst showed peak mass activity for MOR as high as 10.4 A mgPt−1, which is 20.8 times higher than the 20% Pt/C. The catalyst also showed robust long‐term stability with slight current density decay after 100 hours at 35 mA cm−2. Structural characterization, experimental, and theoretical studies show that the electron donation from bromine makes the surface of platinum catalysts highly electron‐rich, and can strengthen the adsorption of CO as well as enhance π back‐donation of Pt to weaken the C−O bond to facilitate CO electrooxidation and enhance catalytic performance during MOR. The results highlight the importance of electron‐rich structure among active sites in Pt‐halogen catalysts and provide detailed insights into the new mechanism of CO electrooxidation to overcome CO poisoning at the Pt center on an orbital level.

Rapid one-step aqueous synthesis of porous PtAg wavy nanochains for methanol electrooxidation with a high CO-tolerance

Tailored morphology of porous binary Pt-based nanostructures is a powerful way to improve their catalytic properties. Herein, we develop a facile aqueous solution approach for the rational one-step synthesis of PtAg nanochains via direct nucleation followed by the oriented attachment growth mechanism under sonication at room temperature. This allows the green and simple fabrication of PtAg wavy nanochains (200 nm length and 20 nm width) with spatially interconnected pores (10 nm) and a high surface area (55.02 m2/g). These merits endowed the methanol oxidation reaction (MOR) performance of PtAg nanochains with a mass activity of (1.12 mA/µgPt) that was about 1.83, 2.8, and 3.11 times higher than those of PtAg nanodendrites, Pt nanodendrites, and commercial Pt/C, respectively, owing to porous nanochain morphology and alloying effect. Intriguingly, visible-light irradiation enhances the MOR performance of PtAg nanochain by nearly 1.5 times, owing to its great photoelectric response properties. The MOR activity of PtAg nanochains is among the highest reported Pt-based electrocatalysts. The presented method may open new edges on the rational design of porous Pt-based nanoarchitecture for various catalytic applications.

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.

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.

Efficient and stable PtFe alloy catalyst for electrocatalytic methanol oxidation with high resistance to CO

Direct methanol fuel cells (DMFC) are widely considered to be an ideal green energy conversion device but their widespread applications are limited by the high price of the Pt-based catalysts and the instability in terms of surface CO toxicity in long-term operation. Herein, the PtFe alloy nanoparticles (NPs) with small particle size (∼4.12 nm) supported on carbon black catalysts with different Pt/Fe atomic ratios (Pt1Fe2/C, Pt3Fe4/C, Pt1Fe1/C, and Pt2Fe1/C) are successfully prepared for enhanced anti-CO poisoning during methanol oxidation reaction (MOR). The optimal atomic ratio of Pt/Fe for the MOR is 1:2, and the mass activity of Pt1Fe2/C (5.40 A mg−1Pt) is 13.5 times higher than that of conventional commercial Pt/C (Pt/C-JM) (0.40 A mg−1Pt). The introduction of Fe into the Pt lattice forms the PtFe alloy phase, and the electron density of Pt is reduced after forming the PtFe alloy. In-situ Fourier transform infrared results indicate that the addition of oxyphilic metal Fe has reduced the adsorption of reactant molecules on Pt during the MOR. The doping of Fe atoms helps to desorb toxic intermediates and regenerate Pt active sites, promoting the cleavage of C–O bonds with good selectivity of CO2 (58.1%). Moreover, the Pt1Fe2/C catalyst exhibits higher CO tolerance, methanol electrooxidation activity, and long-term stability than other PtxFey/C catalysts.

Electron-distribution control via Pt/NC and MoC/NC dual junction: Boosted hydrogen electro-oxidation and theoretical study

The scarcity, high cost and susceptibility to CO of Platinum severely restrict its application in alkaline hydrogen oxidation reaction (HOR). Hybridizing Pt with other transition metals provides an effective strategy to modulate its catalytic HOR performance, but at the cost of mass activity due to the coverage of modifiers on Pt surface. Herein, we constructed dual junctions’ Pt/nitrogen-doped carbon (Pt/NC) and δ-MoC/NC to modify electronic structure of Pt via interfacial electron transfer to acquire Pt-MoC@NC catalyst with electron-deficient Pt nanoparticles, simultaneously endowing it with high mass activity and durability of alkaline HOR. Moreover, the unique structure of Pt-MoC@NC endows Pt with a high CO-tolerance at 1,000 ppm CO/H2, a quality that commercial Pt-C catalyst lacks. The theoretical calculations not only confirm the diffusion of electrons from Pt/NC to MoC/NC could occur, but also demonstrate the negative shift of Pt d-band center for the optimized binding energies of *H, *OH and CO.

Near-Atomic-Scale Superfine Alloy Clusters for Ultrastable Acidic Hydrogen Electrocatalysis.

As a commercial electrode material for proton-exchange membrane water electrolyzers and fuel cells, Pt-based catalysts still face thorny issues, such as insufficient mass activity, stability, and CO tolerance. Here, we construct a bifunctional catalyst consisting of Pt-Er alloy clusters and atomically dispersed Pt and Er single atoms, which exhibits excellent activity, durability, and CO tolerance of acidic hydrogen evolution and oxidation reactions (HER and HOR). The catalyst possesses a remarkably high mass activity and TOF for HER at 63.9 times and 7.2 times more than that of Pt/C, respectively. More impressively, it can operate stably in the acidic electrolyte at 1000 mA cm-2 for more than 1200 h, thereby confirming its potential for practical applications at the industrial current density. In addition, the catalyst also demonstrates a distinguished HOR performance and outstanding CO tolerance. The synergistic effects of active sites give the catalyst exceptional activity for the hydrogen reaction, while the introduction of Er atoms greatly enhances its stability and CO tolerance. This work provides a promising idea for designing low-Pt-loading acidic HER electrocatalysts that are durable at ampere-level current densities and for constructing HOR catalysts with high CO tolerance.

Investigation of water effects on hydrogen dissolution, diffusion, and reaction in high temperature proton exchange membrane fuel cell

High-temperature proton exchange membrane fuel cell with phosphoric acid-doped polybenzimidazole membrane is typically utilized with a methanol steam reformer due to its high CO tolerance. However, methanol reformate commonly contains 20 % water, and its effect on the high temperature fuel cell is unclear. A comprehensive 3D multiphase non-isothermal model with an enhanced electrochemical kinetics model considering the water influence mechanism is developed. The water influence mechanism includes the proton conductivity, hydrogen dissolution on the pore-ionomer interface, hydrogen diffusion inside the ionomer, and hydrogen surface reaction on the platinum. The sensitivity analysis found that hydrogen dissolution on the pore-ionomer and hydrogen surface reaction on the platinum significantly affect cell performance. The influences of water on ionomer hydrogen concentration, platinum surface hydrogen concentration, and surface reaction rates are investigated under the voltage range of 0.9–0.4 V. The increase of water content can improve the net adsorption rate and benefit electrochemical reaction. Besides, the anode water is better for the uniformity of surface reaction rate distributions while not affecting the hydrogen distributions inside the ionomer and on the platinum surface. Additionally, the positive influence of water on CO poisoning is investigated in terms of surface reaction. The water's beneficial effect on decreasing platinum loading is also discussed. The results show that 20 % water can reduce the platinum loading by 20 %.