CO Tolerance Research Articles

Pb-Modified Ultrathin RuCu Nanoflowers for Active, Stable, and CO-resistant Alkaline Electrocatalytic Hydrogen Oxidation.

blem for hydrogen oxidation reaction (HOR), the anodic reaction of hydroxide exchange membrane fuel cell (HEMFC) for converting H2 to electric energy in sustainable manner. We demonstrate here an ultrathin Ru-based nanoflower modified with Pb (PbRuCu NF) as an active, stable, and CO-resistant catalyst for alkaline HOR. Mechanism studies show that the presence of Pb can weaken the adsorption of *H, strengthen *OH adsorption to facilitate CO oxidation, as a result of significantly enhanced HOR activity and improved CO tolerance. Furthermore, in-situ electrochemical attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) suggest that Pb acted as oxygen-rich site to regulate the behavior of the linear CO adsorption. The optimized Pb1.04-Ru92Cu8/C displays a mass activity and specific activity of 1.10 A mgRu-1 and 5.55 mA cm-2, which are ~10 and ~31 times higher than those of commercial Pt/C. This work provides a facile strategy for the design of Ru-based catalyst with high activity and strong CO-resistance for alkaline HOR, which may promote the fundamental researches on the rational design of functional catalysts.

Pb‐Modified Ultrathin RuCu Nanoflowers for Active, Stable, and CO‐resistant Alkaline Electrocatalytic Hydrogen Oxidation

AbstractCO poisoning of Pt group metal (PGM) catalysts is a chronic problem for hydrogen oxidation reaction (HOR), the anodic reaction of hydroxide exchange membrane fuel cell (HEMFC) for converting H2 to electric energy in sustainable manner. We demonstrate here an ultrathin Ru‐based nanoflower modified with Pb (PbRuCu NF) as an active, stable, and CO‐resistant catalyst for alkaline HOR. Mechanism studies show that the presence of Pb can weaken the adsorption of *H, strengthen *OH adsorption to facilitate CO oxidation, as a result of significantly enhanced HOR activity and improved CO tolerance. Furthermore, in situ electrochemical attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) suggests that Pb acts as oxygen‐rich site to regulate the behavior of the linear CO adsorption. The optimized Pb1.04‐Ru92Cu8/C displays a mass activity and specific activity of 1.10 A mgRu−1 and 5.55 mA cm−2, which are ≈10 and ≈31 times higher than those of commercial Pt/C. This work provides a facile strategy for the design of Ru‐based catalyst with high activity and strong CO‐resistance for alkaline HOR, which may promote the fundamental researches on the rational design of functional catalysts.

A real proton‐conductive, robust, and cobalt‐free cathode for proton‐conducting solid oxide fuel cells with exceptional performance

AbstractThe development of proton, oxygen‐ion, and electron mixed conducting materials, known as triple‐conduction materials, as cathodes for proton‐conducting solid oxide fuel cells (H‐SOFCs) is highly desired because they can increase fuel cell performance by extending the reaction active area. Although oxygen‐ion and electron conductions can be measured directly, proton conduction in these oxides is usually estimated indirectly. Because of the instability of cathode materials in a reducing environment, direct measurement of proton conduction in cathode oxide is difficult. The La0.8Sr0.2Sc0.5Fe0.5O3–δ (LSSF) cathode material is proposed for H‐SOFCs in this study, which can survive in an H2‐containing atmosphere, allowing measurement of proton conduction in LSSF by hydrogen permeation technology. Furthermore, LSSF is discovered to be a unique proton and electron mixed‐conductive material with limited oxygen diffusion capability that is specifically designed for H‐SOFCs. The LSSF is an appealing cathode choice for H‐SOFCs due to its outstanding CO2 tolerance and matched thermal expansion coefficient, producing a record‐high performance of 2032 mW cm−2 at 700°C and good long‐term stability under operational conditions. The current study reveals that a new type of proton–electron mixed conducting cathode can provide promising performance for H‐SOFCs, opening the way for developing high‐performance cathodes.

Enhancing ethanol electrooxidation stability catalyzed by Pt with SnO2 modified graphene as support

Developing catalysts for the stable electrooxidation of ethanol have been a goal pursued by scientists. The present work reports a facile synthesis of catalysts with a double junction structure of Pt and SnO2 on graphene (Pt/SnO2GN) through sol–gel combined with glycol hydrothermal reduction method. The physicochemical analyses show that the reduced Pt uniformly dispersed on GN is located adjacent to SnO2 and has electronic interaction with the composite carrier. The electrochemical results exhibit that Pt/SnO2GN has better catalytic performance for ethanol electrooxidation than PtSnO2/GN and PtSn/GN. The ethanol oxidation peak current density on Pt/SnO2GN, after 1500 cycles of voltammetric testing, can still maintain 99.2% of the highest. The excellent catalytic stability of Pt/SnO2GN is ascribed to the double junction structure and the appropriate interaction between Pt and SnO2 on GN, which enlarge the ECSA of Pt, improve the structural integrity, accelerate the charge transfer kinetics and increase the CO tolerance.

Perovskite SrCo0.5Fe0.25Cu0.2Nb0.05O3-δ cathode for intermediate-temperature solid oxide fuel cells: Improved working stability and CO2 tolerance

Commercial solid oxide fuel cells (SOFCs) primarily operate in the intermediate temperature range (600 °C–800 °C); hence, developing cathode materials with good stability and excellent catalytic activity in this temperature range is necessary. Herein, we are reporting the performance of SrCo0.5Fe0.5O3−δ (SCF) and SrCo0.5Fe0.25Cu0.2Nb0.05O3−δ (SCFCN) perovskite oxide as cathode materials for solid oxide fuel cells (SOFCs). The SCFCN sample maintains a cubic structure under a CO2 atmosphere. The polarization resistance of the SCFCN cathode on La0.9Sr0.1Ga0.83Mg0.17O3−δ (LSGM) reaches 0.067 Ωcm2 at 700 °C. The charge transfer and oxygen reduction reactions of the SCFCN cathode on the LSGM electrolyte are the main rate-limiting steps at 600 °C–700 °C. The SCFCN cathode maintains good electrochemical stability during a 200-h test with a configuration of SCFCN/LSGM/SCFCN symmetrical cell. Compared with SCF, the doping of Cu and Nb effectively reduces the Rp attenuation of SCFCN from 0.00012 to 0.00005 Ωcm2/h. The output power density of the fuel cell with SCFCN as the cathode on LSGM reaches 1124 mWcm−2 at 800 °C. This indicates that SCFCN can be a potential material for fabricating cathode for intermediate-temperature SOFCs (IT-SOFCs).

Surface manipulation of a triple-conducting cathode for protonic ceramic fuel cells to enhance oxygen reduction activity and CO2 tolerance

One of the main obstacles limiting the performance of protonic ceramic fuel cells (PCFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR) at reduced temperatures. Here, the surface manipulation of a triple-conducting cathode BaCe0.5Pr0.3Y0.2O3−δ (BCPY) by an efficient catalyst coating PrNi0.5Co0.5O3−δ (PNC) to enhance the ORR activity and CO2 tolerance is reported. The developed PNC-coated BCPY cathode achieves the polarization resistance of 0.25 and 1.00 Ω cm2 at 600 and 500 °C, respectively, approximately 1/5 of that for the pristine BCPY cathode (0.99 and 4.79 Ω cm2), while maintaining an excellent CO2 tolerance. The single cell on a BaZr0.8Yb0.2O3−δ electrolyte also exhibits a high peak power density of 0.79 W cm−2 at 700 °C and a stable operation for 200 h at 600 °C. Such high ORR activity is mainly attributed to the synergistic effect of BCPY support and PNC nanoparticles. Namely, BCPY provides a triple-conducting path (mainly protons), and PNC nanoparticles facilitates surface oxygen exchange and steam adsorption/desorption processes due to the enriched surface oxygen vacancies. This study will provide a new design strategy for developing high-performance PCFCs cathode.

Modeling and Simulation of a High Temperature Proton Exchange Membrane Fuel Cell

High temperature (HT) (around 120-200°C) PEM FCs are predicted to be the next generation of PEMFCs particularly for hydrogen-powered automobiles and combined heat and power (CHP) systems because the water management can be simplified at such temperatures as only a single phase of water vapor needs to be considered. Additionally, the cooling system can be streamlined due to an increase in temperature gradient between the coolant and the FC stack. This will also allow easy recovery of waste heat that can be used as a practical heat source. Furthermore, the CO tolerance improves dramatically at high temperatures thereby allowing HT PEMFCs to utilize reformed and impure hydrogen.A single phase three-dimensional, steady-state, isothermal model for a single 5 HT PEM fuel cell with serpentine flow channels is implemented in COMSOL to investigate the effect of various operating conditions like temperature, back pressure and cathode flow rate and design parameters like catalyst layer loading, cathode GDL porosity, and flow field channels including parallel and interdigitated channels. Different performance indicators in terms of polarization curve, loss mechanisms, oxygen molar concentration, and anode and cathode pressure are represented for a complete overall analysis. In fact, the breakdown of different overpotential loss mechanism for HT PEMFC presented here is unique that not only quantifies these losses but also provides an accurate comparison with corresponding low temperature counterpart. The result from the computational model follows the experimental result very closely, thus, validating our model. The simulations stipulates that the performance of a HT PEMFC improves with increasing temperature, back pressure, and air flow rate. Increasing catalyst layer loading improves the performance up to a point after which it starts to drop at low voltages because of hindered gas diffusion. Similarly, a comparative study among different flow field channel is also presented indicating improved performance when going from parallel to interdigitated and serpentine channels. Furthermore, this study provides guidelines to optimize HT PEMFC performance through comprehensive parametric study.

Sr3Fe1.5Zn0.5O7-δ as Cathode for Protonic-Conducting Solid Oxide Fuel Cells with Enhanced Oxygen Reduction Reaction Activity

Common concerns about green energy have led to a wide focus on solid oxide fuel cells (SOFCs) for their environmental friendship and high efficiency. As the most popular electrode, perovskite materials feature the flexible structure and abundant oxygen sites, which correspondingly leads to diverse doping strategies and good electrochemical performance. However, the high operating temperature results in hot corrosion of both cells and encapsulating materials. Operating under various atmospheres, the generated impurities also cause a measure of irreversible degradation. Here, we first introduced Zn to Sr3Fe2O7-δ perovskite cathode in protonic ceramic fuel cells (PCFCs). Ruddlesden-Popper oxides Sr3Fe2-xZnxO7-δ (SFZx, x=0, 0.1, 0.5) were successfully synthesized and exhibited great performance under intermediate temperatures. The polarization resistance is 0.072 Ω·cm-2 which is 47% lower than that of the undoped Sr3Fe2O7-δ, and the maximum peak power density of the single-cell of NiO-BaZr0.1Ce0.7Y0.2O3- δ(BZCY)|BZCY|SFZ05 reaches 523.56 mW·cm-2 at 750℃, increased by 22%. The improvement is attributed to the formation of oxygen vacancies and the larger triple-phase boundary areas. Furthermore, the electrochemical impedance spectra (EIS) and distribution of relaxation time (DRT) results manifest that the rate-limiting steps are accelerated charge transfer and ionic migration processes. Finally, SFZ05 also presented better CO2 tolerance under an atmosphere of 5% CO2/air. These results display that SFZ05 is a promising candidate for a highly active and stable cathode for PCFCs.

Inhibiting in Situ Phase Transition in Ruddlesdenpopper Perovskite Via Tailoring Bond Hybridization for Oxygen Ion Conduction

Owing to the excellent physical and chemical properties, mixed ionic-electronic conducting (MIEC) oxide materials, especially Ruddlesden-Popper (RP) perovskite oxides with the chemical formula of An+1BnO3n+1, are interesting materials for gas separation, solid oxide fuel/electrolysis cells, polymer electrolyte fuel cells, lithium-ion battery, sodium-ion battery, zinc ion battery and metal-air battery. The in-situ phase transition at different temperatures is a common phenomenon for these MIEC oxide materials, which generally exerts a great influence on the properties and functionalities of these materials and finally determines their performance in various applications. However, the in-depth understanding of the mechanism of phase transitions is still limited so far. Element-doping has been recognized as a facile and efficient strategy to improve the oxygen ionic or electronic conductivity or to stabilize the crystal phase structure (inhibiting both ex-situ and in-situ phase transitions) favorable for oxygen ion conduction. Herein, the ex-situ collapse at room temperature of crystal structure together with the generation of impurities in orthorhombic Pr2NiO4 through Mo doping are observed as the rearrangement of praseodymium atoms-based lattice deformation, which could be attributed to the Mo-induced destabilization of the Pr2NiO4 systems. Noteworthy is that, such effect can be prohibited by controlling the doping contents, and the resultant materials would give rise to the inhibition of in-situ phase transition (high temperature) from low order Pr2NiO4 (An+1BnO3n+1 (n=1)) to high order Pr4Ni3O10 (An+1BnO3n+1 (n=3)) by adjusting bond hybridization at the phase interface. Mo-doping can influence the covalent interaction between praseodymium and oxygen and then promotes the mobility of interstitial oxygen. Pr2Ni1-xMoxO4+ δ were further developed as oxygen separation membrane to help further evaluate the performance of oxygen ion conductivity. In Pr2Ni1-xMoxO4+ δ, Mo doping level of x = 0.05 resulted in an oxygen permeation flux of 3.35 mL min-1 cm-2 at 1000 °C, comparing favorably with the literature. Furthermore, membranes made with Pr2Ni0.95Mo0.05O4+ δ showed high permeation stability in air or helium, and exhibits high CO2 tolerance without obvious decline of the oxygen permeation flux during 500 hours at round 900 °C. This work advances our understanding of the ex-situ and in-situ phase transitions of Pr2NiO4-based RP perovskite materials and shows how Mo doping can stabilizes the in-situ phase structure and improves the mobility of interstitial oxygen. Figure 1

Bismuth Incorporation in Palladium Hydride for the Electrocatalytic Ethanol Oxidation with Enhanced CO Tolerance.

Introducing nonmetal and oxophilic metal into palladium (Pd)-based catalysts is beneficial for boosting electrocatalysis, especially regarding the improvement of mass activity (MA) and CO tolerance. Herein, the stable bismuth-doped palladium hydride (Bi/PdH) networks have been successfully fabricated through a simple one-step method. The intercalation of interstitial H atoms expands the lattice of Pd, and the doping of oxophilic metal Bi restrains the adsorption of poisonous intermediates on the surface of Pd, thereby improving the activity and durability of the as-prepared catalysts in the ethanol oxidation reaction (EOR). The obtained Bi/PdH networks manifest a remarkable MA of 8.51 A·mgPd-1, which is 11.18 times higher than that of commercial Pd/C (0.76 A·mgPd-1). The CO-stripping analysis results indicate that Bi doping can significantly prohibit CO adsorption on the surface of the Bi/PdH networks. The density functional theory (DFT) calculations also reveal that Bi doping enhances the OH* adsorption on the catalyst surface and mitigates the interaction between Pd and CO* intermediates, providing deeper insights into the origin of the enhanced EOR activity and CO tolerance. This work describes an impactful path for producing high-performance and durable PdH-based nanocatalysts.

Electron Regulation of Heterostructured Pt/Rh Metallene Boosts Ethylene Glycol Electrooxidation and Hydrogen Evolution.

The research on high-efficiency two-dimensional (2D) catalytic materials for the small-molecule oxidation-assisted hydrogen evolution reaction (HER) is prospective for efficient hydrogen production. Herein, we report heterostructured Pt/Rh metallene with Pt nanoparticles (NPs) uniformly anchored on Rh metallene for the HER and ethylene glycol oxidation reaction (EGOR). The ultrathin sheet structure of the Pt/Rh metallene offers high surface areas and sufficient active sites. More importantly, the Pt/Rh heterostructure can optimize catalytic active centers and adjust electronic structure. Thus, Pt/Rh metallene exhibits superior electrocatalytic HER activity with a low overpotential of 28 mV in 1 M KOH at 10 mA cm-2 and EGOR activity with a specific activity of 8.39 mA cm-2 in 1 M KOH with 3 M EG, along with outstanding CO tolerance. In a two-electrode system, Pt/Rh metallene requires a low potential of 0.51 V for stable and efficient hydrogen production at 10 mA cm-2 in 1 M KOH + 3 M EG, with the simultaneous production of high-value-added products. The job proposes an attractive strategy for the synthesis of 0D/2D metallene toward simultaneous energy-saving hydrogen production and chemical update.

Effect of Zn doping on Sr3Fe2O7-δ Ruddlesden-Popper oxides as active and robust cathodes for protonic ceramic fuel cells

Perovskite oxides are promising electrodes for protonic ceramic fuel cells (PCFCs) due to their good electrochemical performance and stability. However, the lower operating temperature results in a large polarization resistance and sluggish oxygen reduction reaction (ORR) in cathodes. Herein, Ruddlesden-Popper (R–P) type perovskite Sr3Fe2-xZnxO7-δ (SFZx, x = 0, 0.1, 0.5) were successfully synthesized and the partial replacement of Fe by Zn in SFZx demonstrates a superior ORR activity. At 750 °C, the polarization resistance of SFZ05 is 0.072 Ω cm−2, which is 47% lower than that of the undoped Sr3Fe2O7-δ (SFO), and the peak power density of the single-cell with an SFZ05 cathode reaches 523.56 mW cm−2. The distribution of relaxation time (DRT) results manifest that the rate-limiting steps of ORR are charge transfer and ionic migration processes. Furthermore, SFZ05 also presented better CO2 tolerance. These results show that SFZ05 is a promising cathode candidate with high activity and stability for PCFCs.

Formicary-like PtBi1.5Ni0.2Co0.2Cu0.2 high-entropy alloy aerogels as an efficient and stable electrocatalyst for methanol oxidation reaction

High-entropy alloy aerogels (HEAAs) have become promising electrochemical catalysts because of the advantageous combination of high-entropy alloys and aerogel structure. However, how to fabricate 3D porous high-entropy alloys accurately is still a great challenge due to their inherent thermodynamic instability and differences in reduction potentials of metal ions. Herein, PtBi1.5Ni0.2Co0.2Cu0.2 HEAAs have been synthesized by combining co-reduction method and freeze-drying technology. The resulting PtBi1.5Ni0.2Co0.2Cu0.2 HEAAs have the structural and morphological benefits of both high-entropy alloys and aerogels. Both XPS and DFT results confirm that the d-band center of PtBi1.5Ni0.2Co0.2Cu0.2 HEAAs shifts to lower binding energy compared to Pt/C, indicating the effective regulation of electronic structure on the surface of PtBi1.5Ni0.2Co0.2Cu0.2 HEAAs. As a demonstration in the methanol oxidation reaction (MOR), a mass activity of 4.19 A mgPt−1 and long-term stability (>0.33 A mgPt−1 after 10 cycles of 3600 s stability test) can be obtained on the PtBi1.5Ni0.2Co0.2Cu0.2 HEAAs, outperforming binary Pt-based alloys and commercial Pt/C. The CO adsorption strength of PtBi1.5Ni0.2Co0.2Cu0.2 HEAAs is more weaker than that of PtBi1.5 alloys and Pt/C, which proves the enhanced CO tolerance. The results pave the way for fabricating the hybrids of high-entropy alloys and aerogels with superior activity and stability.

Ultrathin PtNiGaSnMoRe Senary Nanowires with Partial Amorphous Structure Enable Remarkable Methanol Oxidation Electrocatalysis

AbstractFinding a high CO‐tolerance Pt‐based catalyst plays a critical role for direct methanol fuel cells. Therefore, it is necessary to design controllable nanostructure and composition. Herein, a synthesis of ultrathin PtNiGaSnMoRe senary nanowires (SNWs) that features the virtues of partial amorphous structure, multimetallic ensembles, and ultrathin diameter is reported. For the alkaline methanol oxidation reaction (MOR), the SNWs deliver an excellent mass activity of 6.2 A mg−1Pt and a specific activity of 12.3 mA cm−2, respectively. More significantly, after undergoing 10 000 s of a durability test, its mass activity remains 13.0 times higher than that of commercial Pt/C catalyst, which is mainly attributed to the faster CO‐intermediate (CO*) removal and advanced nanostructure. In situ Fourier transform infrared (FTIR) spectroscopies and CO stripping experiments indicate its remarkable resistance to CO poisoning. Theoretical studies further reveal that the SNWs enable reduced energy barriers for the conversion of CO* into COOH* derived from the decreased CO* binding and intensified OH adsorption that accelerate the combination of both, thus essentially improving the MOR performance and CO tolerance.

Focused microwave-assisted synthesis of activated XC-72R supported PdBi nanocatalyst for the enhanced electrocatalytic performance in formic acid oxidation

The present paper describes a rapid and straightforward synthesis technique called focused microwave-assisted synthesis (FMWS) for producing bimetallic carbon-based PdBi@C nanocomposites with desired monodispersity and uniformity and investigates their catalytic activity towards formic acid electro-oxidation reaction (FAOR). X-ray diffraction (XRD), transmission electron microscope (TEM), and energy dispersive X-ray (EDX) analysis confirmed that Pd atoms are embedded in the activated XC-72 R carbon support, and the resulting Pd@C surface shows excellent integration with Bi atoms via spontaneous chemisorption after FMWS. The synthesized Pd20Bi1@C nanocatalyst displayed optimal electrochemical performance for direct formic acid oxidation reaction (DFAOR), with uniform dispersity, a narrow size distribution (6.54 ± 1.03 nm), and a polydispersity index (PDI) of 16%, indicating high monodispersity achieved through FMWS. The influence of nanocomposite content on DFAOR was investigated, revealing that Pd20Bi1@C exhibited a significantly higher current density compared to salt Pd@C, with a 2.63-fold increase. The evaluated nanocatalysts ranked in descending order of final current densities (mAcm−2) as follows: Pd20Bi1@C (21.06) > Pd30Bi1@C (14.31) > Pd40Bi1@C (12.09) > Pd10Bi1@C (9.22) > Pd@C (8.02). Furthermore, chronoamperometry and cyclic voltammetry tests demonstrated that the addition of Bi to Pd@C enhanced the reaction of oxygenated species with CO-like poisonous intermediates, thereby facilitating the adsorption and oxidation of formic acid molecules by releasing Pd active sites in DFAOR. Notably, Pd20Bi1@C exhibited exceptional stability and improved CO tolerance. In summary, the current study highlights the potential of integrating FMWS with a chemisorption approach to achieve excellent electrochemical performance, enabling nanocomposites to demonstrate enhanced feasibility as prospective catalysts for FAOR.

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 %.

Highly Selective Synthesis of Monoclinic-Phased Platinum-Tellurium Nanotrepang for Direct Formic Acid Oxidation Catalysis.

Designing efficient formic acid oxidation reaction (FAOR) catalysts with remarkable membrane electrode assembly (MEA) performance in a direct formic acid fuel cell (DFAFC) medium is significant yet challenging. Herein, we report that the monoclinic-phased platinum-tellurium nanotrepang (m-PtTe NT) can be adopted as a highly active, selective, and stable FAOR catalyst with a desirable direct reaction pathway. The m-PtTe NT exhibits the high specific and mass activities of 6.78 mA cm-2 and 3.2 A mgPt-1, respectively, which are 35.7/22.9, 2.8/2.6, and 3.9/2.9 times higher than those of commercial Pt/C, rhombohedral-phased Pt2Te3 NT (r-Pt2Te3 NT), and trigonal-phased PtTe2 NT (t-PtTe2 NT), respectively. Simultaneously, the highest reaction tendency for the direct FAOR pathway and the best tolerance to poisonous CO intermediate can also be realized by m-PtTe NT. More importantly, even in a single-cell medium, the m-PtTe NT can display a much higher MEA power density (171.4 mW cm-2) and stability (53.2% voltage loss after 5660 s) than those of commercial Pt/C, demonstrating the great potential in operating DFAFC device. The in-situ Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy jointly demonstrate that the unique nanostructure of m-PtTe NT can effectively optimize dehydrogenation steps and inhibit the CO intermediate adsorption, as well as promote the oxidation of noxious CO intermediate, thus achieving the great improvement of FAOR activity, poisoning tolerance, and stability. Density functional theory calculations further reveal that the direct pathway is the most favorable on m-PtTe NT than r-Pt2Te3 NT and t-PtTe2 NT. The higher activation energy to produce CO and the relatively weaker binding with CO of m-PtTe NT result in the better CO tolerance. This work achieves remarkable FAOR and MEA performances of advanced Pt-based anodic catalysts for DFAFCs via a phase engineering strategy.

Low-Pt Octahedral PtCuCo Nanoalloys: "One Stone, Four Birds" for Oxygen Reduction and Methanol Oxidation Reactions.

To find a low-Pt electrocatalyst that is functionally integrated and superior to the state-of-the-art single-Pt electrocatalyst is expectedly a challenge. We have in this study found that the reactivity of the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR), in both acidic and alkaline electrolytes (viz., four half-cell reactions), can be modified and greatly enhanced by the electronic and/or synergistic effects of a low-Pt octahedral PtCuCo alloy. For the ORR, the mass activity (MA) of Pt0.23Cu0.64Co0.13/C in an acidic or alkaline electrolyte was 14.3 or 10.7 times that of the commercial Pt/C. For the MOR, the MA of Pt0.23Cu0.64Co0.13/C in an acidic or alkaline electrolyte was 7.2 or 3.4 times that of the commercial Pt/C. In addition, Pt0.23Cu0.64Co0.13/C exhibited an increased durability and CO tolerance, as compared with the commercial Pt/C. Density functional theory calculations demonstrated that the PtCuCo(111) surface can effectively optimize the O* binding energy. This work has successfully shown an example of how both acidic and alkaline ORR and MOR activities can be significantly synchronously enhanced.

Embedding oxophilic rare-earth single atom in platinum nanoclusters for efficient hydrogen electro-oxidation

Designing Pt-based electrocatalysts with high catalytic activity and CO tolerance is challenging but extremely desirable for alkaline hydrogen oxidation reaction. Herein we report the design of a series of single-atom lanthanide (La, Ce, Pr, Nd, and Lu)-embedded ultrasmall Pt nanoclusters for efficient alkaline hydrogen electro-oxidation catalysis based on vapor filling and spatially confined reduction/growth of metal species. Mechanism studies reveal that oxophilic single-atom lanthanide species in Pt nanoclusters can serve as the Lewis acid site for selective OH- adsorption and regulate the binding strength of intermediates on Pt sites, which promotes the kinetics of hydrogen oxidation and CO oxidation by accelerating the combination of OH− and *H/*CO in kinetics and thermodynamics, endowing the electrocatalyst with up to 14.3-times higher mass activity than commercial Pt/C and enhanced CO tolerance. This work may shed light on the design of metal nanocluster-based electrocatalysts for energy conversion.

WO3 -Assisted Synergetic Effect Catalyzes Efficient and CO-Tolerant Hydrogen Oxidation for PEMFCs.

Developing anode catalysts with substantially enhanced activity for hydrogen oxidation reaction (HOR) and CO tolerance performance is of great importance for the commercial applications of proton exchange membrane fuel cells (PEMFCs). Herein, an excellent CO-tolerant catalyst (Pd-WO3 /C) has been fabricated by loading Pd nanoparticles on WO3 via an immersion-reduction route. A remarkably high power density of 1.33W cm-2 at 80 °C is obtained by using the optimized 3Pd-WO3 /C as the anode catalyst of PEMFCs, and the moderately reduced power density (73% remained) in CO/H2 mixed gas can quickly recover after removal of CO-contamination from hydrogen fuel, which is not possible by using Pt/C or Pd/C as anode catalyst. The prominent HOR activity of 3Pd-WO3 /C is attributed to the optimized interfacial electron interaction, in which the activated H* adsorbed on Pd species can be effectively transferred to WO3 species through hydrogen spillover effect and then oxidized through the H species insert/output effect during the formation of Hx WO3 in acid electrolyte. More importantly, a novel synergetic catalytic mechanism about excellent CO tolerance is proposed, in which Pd and WO3 respectively absorbs/activates CO and H2 O, thus achieving the CO electrooxidation and re-exposure of Pd active sites for CO-tolerant HOR.