CO Electrooxidation Research Articles

OH Regulator of Amorphous CrOx on Defect-Rich Ultrafine Pd Nanowires Boosts Electrocatalytic Ethanol Oxidation.

Reasonable construction of high activity and selectivity electrocatalysts is crucial to achieve efficient ethanol oxidation reaction (EOR). However, the oxidation of ethanol tends to produce CO species that poison the active centers of the EOR electrocatalysts. Herein, a unique amorphous CrOx-protected defect-rich ultrafine Pd nanowires (CrOx-Pd NWs) is developed. On the one hand, the CrOx layer can act as a protective layer to maintain the structure of the nanowire. On the other hand, it can play the role of OH regulator to optimize the adsorption energy barrier of intermediate species in Pd nanowire, thereby enhancing the ability of the catalyst to resist CO poisoning. The CrOx-Pd NWs exhibit excellent EOR performance with 3.64 times higher mass activity and 50mV lower CO electro-oxidation potential than commercial Pd black. The results show that the CrOx layer promotes the dissociation of H2O into OHads, while the CrOx transfers electrons to neighboring Pd atoms optimizing the electronic configuration of Pd, thus selectively oxidizing ethanol to acetate and preventing the formation of toxic *CO. This work provides an effective strategy for the synthesis of nanowire materials with oxide/metal interfaces and offers new ideas for the design of catalysts that can efficiently drive EOR.

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.

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.

Step-by-Step Nanoscale Top-Down Blocking and Etching Lead to Nanohexapods with Cartesian Geometry.

In this research, we designed a stepwise synthetic method for Au@Pt hexapods where six elongated Au pods are arranged in a pairwise perpendicular fashion, sharing a common point (the central origin in a Cartesian-coordinate-like hexapod shape), featured with tip-selectively decorated Pt square nanoplates. Au@Pt hexapods were successfully synthesized by applying three distinctive chemical reactions in a stepwise manner. The Pt adatoms formed discontinuous thin nanoplates that selectively covered six concave facets of a Au truncated octahedron and served as etching masks in the succeeding etching process, which prevented underlying Au atoms from being oxidized. The subsequent isotropic etching proceeded radially, starting from the bare Au surface, carving the central nanocrystal in a concave manner. By controlling the etching conditions, Au@Pt hexapods were successfully fabricated, wherein the core Au domain is connected to six protruding arms, which hold Pt nanoplates at the ends. Due to their morphology, Au@Pt hexapods feature distinctive optical properties in the near-infrared region, as a proof of concept, allowing for surface-enhanced Raman spectroscopy (SERS)-based monitoring of in situ CO electrooxidation. We further extended our synthetic library by tailoring the size of the Pt nanoplates and neck widths of Au branches, demonstrating the validity of selective blocking and etching-based colloidal synthesis.

Molybdenum‐based Nanocatalysts for CO Oxidation Reactions in Direct Alcohol Fuel Cells: A Critical Review

AbstractCarbon monoxide (CO) oxidation is crucial in fuel cell anodes. Recent research has focused on electrocatalysts that synergistically enhance CO oxidation alongside alcohol/hydrogen oxidation. High sensitivity and selectivity for CO oxidation at lower onset potentials are the key objectives. Molybdenum (Mo) has emerged as a promising non‐noble transition metal co‐catalyst for CO oxidation. Mo versatility arises from its ability to alloy with Pt and mix with other non‐noble transition metals in various forms (MoOx, MoS2, MoC). Carbon‐supported Mo nanoparticles have shown potential in reducing Pt loading and improving CO tolerance due to Mo oxyphilic properties, effectively oxidizing weakly adsorbed CO and lowering onset and peak potentials. However, challenges persist, such as a limited potential window for CO oxidation and decreased CO adsorption affinity at higher potentials. Addressing these issues requires understanding factors affecting Mo‐based electrocatalysts (Mo‐ECs) activity, including PtMo alloy composition, Mo′s chemical state, cell temperature, and the role of carbon support. This article provides a comprehensive review of Mo‐ECs role in CO electrooxidation in direct alcohol fuel cells (DAFCs) over the past two decades.

Atomically Dispersed CrOX on Pd Metallene for CO-Resistant Methanol Oxidation.

The effective design and construction of high-performance methanol oxidation reaction (MOR) electrocatalysts are significant for the development of direct methanol fuel cells. But the active sites of the MOR electrocatalysts are susceptible to being poisoned by CO, resulting in poor durability. Herein, we report an atomically dispersed CrOX species anchored on Pd metallene through bridging O atoms. This catalyst shows an outstanding MOR performance with 7 times higher mass activity and 100 mV lower CO electrooxidation potential than commercial Pd/C. The results of operando electrochemical Fourier transform infrared spectroscopy demonstrate the rapid removal of CO* on CrOX-Pd metallene. Theoretical calculations reveal that atomically dispersed CrOX can lower the adsorption energy of CO* on Pd sites and enhance that of OH* through the formation of a hydrogen bond, decreasing the formation energy of COOH*. This work provides a new strategy for improving MOR performance via atomically engineering oxide/metal interfaces.

Characterization of a Nickel / Gadolinia Doped Ceria Fuel Electrode for Co-Electrolysis

Modelling of the high temperature co-electrolysis process requires understanding of the underlying reaction pathways. These include the electrochemical steam reduction, the electrochemical CO2 reduction and their coupling via the catalytic (reverse-)water-gas-shift reaction (RWGS). The assumption of a very fast water-gas-shift reaction and therefore neglectable CO electro-oxidation is widely used. The validity of this assumption has been previously investigated and proven to be sufficient by Kromp et al. [1] for an anode supported cell (ASC) with a nickel / yttria-stabilized zirconia (Ni/YSZ) fuel electrode.Within this contribution we aim to extend the approach by Kromp et al. [1] towards an electrolyte-supported cell (ESC) with a nickel / gadolinium-doped ceria (Ni/CGO) fuel electrode. Previously, it has been proposed, that the electro-oxidation /-reduction of CO / CO2 can be present under reformate gas mixtures [2,3] on Ni/CGO fuel electrodes. However, a detailed comparison of pure activation resistance contributions during different operating modes has not been performed yet.We present results from a complex variation of operating parameters (such as various gas compositions, exemplarily shown in fig. 1) for process identification by the use of electrochemical impedance spectroscopy and the subsequent impedance analysis by the distribution of relaxation times (DRT). Visualization and deconvolution of gas diffusion impedance contributions is done via the evaluation of the polarization resistance differences with different inert gases. This has been successfully applied for binary gas mixtures of hydrogen and steam [4] and also CO2 and CO. [5] The applicability of this method towards more complex multicomponent gas mixtures incorporating hydrogen, steam, CO2 and CO will be shown. By subtracting the gas diffusion impedance contributions, it is possible to evaluate reaction kinetics of the underlying activation polarization and a meaningful comparison of operation modes is facilitated. The ratio of direct CO2electro-reduction and CO2-conversion by RWGS will be discussed for different compositions and temperatures to show a non-neglectable influence of the CO2 electroreduction at even lower pCO2 / pH2 ratios than previously reported. Furthermore, we compare our results with ones obtained from Ni/YSZ fuel electrodes, to investigate the influence of fuel electrode structure and material.

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.

Theoretical Investigation of the Electrochemical Oxidation of H2 and CO Fuels on a Ruddlesden-Popper SrLaFeO4-δ Anode.

The electrochemical oxidation of H2 and CO fuels have been investigated on the Ruddlesden-Popper layered perovskite SrLaFeO4-δ (SLF) under anodic solid oxide fuel cell conditions using periodic density functional theory and microkinetic modeling techniques. Two distinct FeO2-plane-terminated surface models differing in terms of the underlying rock salt layer (SrO or LaO) are used to identify the active site and limiting factors for the electro-oxidation of H2, CO, and syngas fuels. Microkinetic modeling predicted an order of magnitude higher turnover frequency for the electro-oxidation of H2 compared to CO for SLF at short-circuit conditions. The surface model with an underlying SrO layer was found to be more active with respect to H2 oxidation than the LaO-based surface model. At an operating voltage of less than 0.7 V, surface H2O/CO2 formation was found to be the key rate-limiting step, and the surface H2O/CO2 desorption was the key charge transfer step. In contrast, the bulk oxygen migration process was found to affect the overall rate at high cell voltage conditions above 0.9 V. In the presence of syngas fuel, the overall electrochemical activity is derived mainly from H2 electro-oxidation and CO2 is chemically shifted to CO via the reverse water-gas shift reaction. Substitutional doping of a surface Fe atom with Co, Ni, and Mn revealed that the H2 electro-oxidation activity of FeO2-plane terminated anodes with an underlying LaO rock salt layer can be improved with dopant introduction, with Co yielding a three orders of magnitude higher activity relative to the undoped LaO surface model. Constrained ab initio thermodynamic analysis furthermore suggested that the SLF anodes are resistant toward sulfur poisoning both in the presence and absence of dopants. Our findings reflect the role of various elements in controlling the fuel oxidation activity of SLF anodes that could aid the development of new Ruddlesden-Popper phase materials for fuel cell applications.

Modeling the electrooxidation of CO on the catalyst with heterogeneous sites

The distribution and type of exposed surface sites are essential aspects of kinetics which should be considered together with mass transport in an electrochemical process, since multiple types of functional sites may coexist on electrocatalyst surfaces. In this study, we categorize the surface sites into active sites where the dissociation of water molecule and CO oxidation take place and nonactive sites where CO is adsorbed. By solving the bulk diffusion, adsorption, surface diffusion and reaction using the Fick’s diffusion law, reaction rate law, and Butler-Volmer equation, it is shown that the catalysts surface with a certain ratio of nonactive sites possesses high current rather than only with a type of active sites. More importantly, the high steady-state current can be obtained by balancing the micro-kinetics and mass transport. The findings provide a new strategy of catalyst design and electrochemical operation.

Electrooxidation of CO on Platinum Nanoparticles Supported on NiO Thin Films

In this article, we report on a robust experimental model to investigate strong metal–support interactions (SMSI) and their effect on electrocatalytic reactions in the absence and presence of direct contact between the nanoparticles (NPs) and the metal oxide thin film. Specifically, we describe beneficial interactions between Ni0.9O thin film supports and PtNPs toward the CO electrooxidation reaction. The metal oxide layer (Ni0.9O) is prepared by atomic layer deposition and characterized using X-ray photoelectron spectroscopy (XPS). PtNPs, containing an average of either 55 (Pt55) or 140 (Pt140) atoms, were synthesized using a dendrimer encapsulation method. The results indicate negative shifts of ∼100 and ∼60 mV of the CO electrooxidation peak potential when Ni0.9O thin films are in contact with Pt55 NPs and Pt140 NPs, respectively. Additionally, the oxygen evolution reaction (OER) is suppressed only when the PtNPs are in contact with the Ni0.9O thin film. Density functional theory (DFT) calculations indicate that both the CO electrooxidation enhancement and suppression of the OER can be attributed to a 1.23 eV decrease of the CO* binding energy and a 0.35 eV increase of the OH* binding energy at a NiO(111)/Pt55 NP interface compared to isolated Pt55 NPs.

EFEITO DOS DEFEITOS DE SUPERFÍCIE E DO pH NA ADSORÇÃO E NA CATÁLISE DA ELETRO-OXIDAÇÃO DE CO EM SUPERFÍCIES MODELOS DE PLATINA

SURFACE DEFECTS AND pH EFFECTS ON ADSORPTION AND CATALYSIS OF CO ELECTRO-OXIDATION ON MODEL PLATINUM SURFACES. Platinum is one of the well-known catalytic materials for which the electro-oxidation of carbon monoxide better behaves as a sensitive reaction to the catalyst surface structure. For the electro-catalytic reactions that behave like this, the rate (faradaic current density) is the result of the sum of the activity of the different active sites working with very different efficiencies or abilities. In this scenario, different atomic arrangements on the catalyst surface are expected to play different roles in surface-catalyzed reactions. In this article, the functionalities that surface defects (steps) can play in the adsorption and electrocatalytic oxidation of CO on model platinum surfaces are reviewed. Surface defects are indirectly related to the up catalysis as well as to the inhibition of reaction pathways of CO electro-oxidation under very particular conditions; these surface entities are also indirectly related to restrictions for the mobility of adsorbed CO on the (111) terraced surfaces. We analyze the selective activation and deactivation of surface sites by the pH effect, and typical catalytic properties of extended surfaces and shaped-controlled nanoparticles have been discussed thoroughly. We present a model of most active sites involved in the pathways of CO2 formation from the electro-oxidation of adsorbed CO.

Pt-O-Cu anchored on Fe2O3 boosting electrochemical water-gas shift reaction for highly efficient H2 generation

Electrochemical water–gas shift (EWGS) reaction is an emerging technology with energy-saving and environmental-friendly advantages to produce high-purity hydrogen form the waste gas containing CO. However, it remains a significant challenge to design superior activity and highly durable EWGS electrocatalysts, particularly with low content of noble metals. Herein, a series of Pt-xCu/Fe2O3 (x = 0, 2, 5) catalysts are synthesized by the complexation precipitation method to construct coupling sites between Pt and CuOx, aiming to optimize the adsorption of CO and the activation of OH–. The obtained 2.5Pt-2Cu/Fe2O3 catalyst presents a unique Pt-O-Cu structure, delivering a much lowest onset potential, high specific activity, and excellent mass activity (1.5 A·mgPt-1) at 0.73 V (vs. RHE), which is over 15 and 3 times that of commercial Pt/C (20%) and unmodified Pt/Fe2O3 catalyst, respectively. Meanwhile, the in-situ X-ray absorption results demonstrate that the facilitated interaction among the Pt-O-Cu structure promotes the high durability of the 2.5Pt-2Cu/Fe2O3 catalyst and the operability at high potential. More importantly, the moderate binding of CO and moderate activation of OH* are suggested for boosting the reactivity in the CO electro-oxidation reaction. In particular, the fabricated Pt||2.5Pt-2Cu/Fe2O3, employed in coupling the HER and CO electro-oxide reaction, shows a remarkable hydrogen production of about 98 mmolH2·h−1·mgPt−1 at 0.8 V (vs. RHE). This work also definitely confirms the possibility of the catalyst being applied to produce hydrogen under practical conditions with different concentrations of CO, even being applied in the purification of trace CO in a hydrogen-rich atmosphere.

Improving Alkaline Hydrogen Oxidation Activity of Palladium through Interactions with Transition-Metal Oxides

Anion-exchange membrane fuel cells (AEMFCs) are a promising electrochemical power generation technology that will most likely find applications in stationary power supply and mobile applications such as electric vehicles in the future. One of the main technological challenges with AEMFCs is developing catalysts with improved activities to reduce the current overpotential losses in the cell. A historically underappreciated challenge for AEMFC catalyst development is the sluggish hydrogen oxidation reaction (HOR) kinetics at the anode that still requires high loadings of platinum group metals. Here, we demonstrate that the alkaline HOR activity of palladium nanoparticles is enhanced through strong interactions with transition-metal oxides. A series of transition-metal oxides in the IV oxidation state (ZrO2, CeO2, SnO2, and RuO2) were deposited onto Vulcan XC-72 carbon. Pd nanoparticles (20 wt %) were then grown on each support. This series of catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The alkaline HOR activity was investigated using cyclic voltammetry and linear sweep voltammetry. Of the several systems that were considered, Pd–RuO2/C displayed the highest HOR surface-specific activity (49 μA cmPd–2). It had an onset for CO electro-oxidation at around 200 mV, which is lower than the other materials analyzed herein. The results were explained using first-principles calculations by investigating Tafel and Volmer reactions. These results suggested that increased HOR activity is favored by the population of the Pd surface with OH– groups at lower overpotentials. These insights are valuable for the future design of next-generation catalysts with high activity toward alkaline HOR required by future high-performance AEMFCs.

Ethanol Electro-Oxidation on Carbon-Supported PtRuCu/C Catalyst in a Proton Exchange Membrane Electrolysis Cell

The electrochemical oxidation of ethanol in cells with proton exchange membrane (PEM) electrolytes is important to develop energy technologies based on bioethanol. Direct ethanol fuel cells (DEFC) have been considered attractive power sources with high potential for use in vehicles and electronic devices, despite their low efficiencies, which need to be increased. On the other hand, ethanol electrolysis cells (EEC) can be used for hydrogen production.The importance of direct ethanol fuel cell technology for a sustainable energy future has resulted in comprehensive studies of the electrochemical oxidation of ethanol and the development of many different anode catalysts.1 Preparing catalysts with high efficiency for the ethanol oxidation reaction has been a major challenge. Although Pt has high activity for ethanol oxidation in acidic media, it is easily poisoned by adsorbed intermediates like COad and CHx, thus high overpotentials are required. PtRu alloy has become important in studies of the oxidation of ethanol, because it has high activity at low potentials. However, product analysis has shown that the main product from the oxidation of ethanol at PtRu is acetic acid and only a small CO2 yield is produced.2 Since increasing the production of CO2 is the major point to enhance the efficiency of DEFCs, it is necessary and crucial to develop and modify PtRu/C. Many researchers have introduced a third transition metal (ternary catalyst) to improve the activity and performance of PtRu/C at high potentials and also to increase the production of CO2.3,4 The purpose of this work is to explore the effect of incorporating Cu into PtRu/C catalysts on the production of CO2. A proton exchange membrane electrolysis cell was used to compare the performance of both PtRu/C and PtRuCu/C catalysts and measure the CO2 yield from the oxidation of ethanol. Interestingly, adding Cu enhanced the production of CO2, and the performance. Acknowledgments This work was supported by the Nature Science and Engineering Research Council of Canada and Memorial University References (1) Akhairi, M. A. F.; Kamarudin, S. K. Catalysts in Direct Ethanol Fuel Cell (DEFC): An Overview. Int. J. Hydrogen Energy 2016, 41, 4214–4228.(2) Altarawneh, R. M.; Pickup, P. G. Product Distributions and Efficiencies for Ethanol Oxidation in a Proton Exchange Membrane Electrolysis Cell. J. Electrochem. Soc. 2017, 164, F861–F865.(3) Xue, S.; Deng, W.; Yang, F.; Yang, J.; Amiinu, I. S.; He, D.; Tang, H.; Mu, S. Hexapod PtRuCu Nanocrystalline Alloy for Highly Efficient and Stable Methanol Oxidation. ACS Catal. 2018, 8, 7578–7584.(4) Barroso, J.; Pierna, A. R.; Blanco, T. C.; Ruiz, N. Trimetallic Amorphous Catalyst with Low Amount of Platinum: Comparative Study for Ethanol, Bioethanol and CO Electrooxidation. Int. J. Hydrogen Energy 2014, 39, 3984–3990.

Effect of Intermediate Semiconducting TiOx Thin Films on Nanoparticle-Mediated Electron Transfer: Electrooxidation of CO.

The concept of nanoparticle-mediated electron transfer (eT) across insulating thin films was elucidated theoretically by Allongue and Chazalviel in 2011. In their model, metal nanoparticles (NPs) are immobilized atop passivating, self-assembled monolayers (SAMs). They found that under certain conditions, related to the thickness of the SAM and the size of the NPs, efficient faradaic oxidation and reduction reactions could proceed at the NP surface. In the absence of NPs, however, eT was suppressed by the insulating SAM thin films. Allongue and Chazalviel concluded that, within certain bounds, eT is mediated by fast tunneling between the conductive electrode and the metal NPs, while the kinetics of the redox reaction are controlled by the NPs. This understanding has been confirmed using a variety of experimental models. The theory is based on electron tunneling; therefore, the nature of the intervening medium (the insulator in prior studies) should not affect the eT rate. In the present manuscript, however, we show that the theory breaks down under certain electrochemical conditions when the medium between conductors is an n-type semiconductor. Specifically, we find that in the presence of either Au or Pt NPs immobilized on a thin film of TiOx, CO electrooxidation does not proceed. In contrast, the exact same systems lead to the efficient reduction of oxygen. At present, we are unable to explain this finding within the context of the model of Allongue and Chazalviel.

Restructuring of 4H phase Au nanowires and its catalytic behavior toward CO electro-oxidation

Au nanowires in 4H crystalline phase (4H Au NWs) are synthesized by colloid solution methods. The crystalline phase and surface structure as well as its performance toward electrochemical oxidation of CO before and after removing adsorbed oleylamine molecules (OAs) introduced from its synthesis are evaluated by high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), underpotential deposition of Pb (Pb-upd) and cyclic voltammetry. Different methods, i.e. acetic acid cleaning, electrochemical oxidation cleaning, and diethylamine replacement, have been tried to remove the adsorbed OAs. For all methods, upon the removal of the adsorbed OAs, the morphology of 4H gold nanoparticles is found to gradually change from nanowires to large dumbbell-shaped nanoparticles, accompanying with a transition from the 4H phase to the face-centered cubic phase. On the other hand, the Pb-upd results show that the sample surfaces have almost the same facet composition before and after removal of the adsorbed OAs. After electrochemical cleaning with continuous potential scans up to 1.3 V, CO electro-oxidation activity of the 4H Au sample is significantly improved. The CO electro-oxidation activity is compared with results on the three basel Au single crystalline surfaces reported in the literature, possible origins for its enhancement are discussed.

Electrolyte buffering species as oxygen donor shuttles in CO electrooxidation

Electrolyte buffering species are shown to act as oxygen donor in the carbon monoxide electrooxidation

Direct Evidence for the Decisive Role of OH* Activation in CO Electro-Oxidation Reaction

Direct Evidence for the Decisive Role of OH* Activation in CO Electro-Oxidation Reaction

Proton exchange membrane fuel cells powered with both CO and H2

The CO electrooxidation is long considered invincible in the proton exchange membrane fuel cell (PEMFC), where even a trace level of CO in H2 seriously poisons the anode catalysts and leads to huge performance decay. Here, we describe a class of atomically dispersed IrRu-N-C anode catalysts capable of oxidizing CO, H2, or a combination of the two. With a small amount of metal (24 μgmetal⋅cm-2) used in the anode, the H2 fuel cell performs its peak power density at 1.43 W⋅cm-2 When operating with pure CO, this catalyst exhibits its maximum current density at 800 mA⋅cm-2, while the Pt/C-based cell ceases to work. We attribute this exceptional catalytic behavior to the interplay between Ir and Ru single-atom centers, where the two sites act in synergy to favorably decompose H2O and to further facilitate CO activation. These findings open up an avenue to conquer the formidable poisoning issue of PEMFCs.