Low Noble Metal Loading Research Articles

Insights into the cyclic CO2 capture and catalytic methanation over highly performing Li-Ru/Al2O3 dual function materials

The combined CO2 capture and in-situ methanation using renewable hydrogen over dual function sorbent-catalyst materials is a chemical looping process with strong potential to increase the efficiency and reduce the cost of current CCU technologies. In this work, we set out to develop highly performing Lithium-Ruthenium/Al2O3 investigating synergic and mechanistic aspects involved in the alternate CO2 adsorption and hydrogenation phases. Catalysts with low Ru loading (max 1% wt.) and fixed dispersion on Al2O3 spheres were promoted with variable amounts of Li (1–5% wt.) and characterized by BET, PSD, XRD, H2 chemisorption, CO2-TPD, TG-MS, H2-TPSRx and CO2 catalytic methanation under continuous flow conditions. Transient CO2 storage/methanation cycles were studied in a fixed bed reactor that was operated at several temperature levels (250–350 °C) with alternate feed conditions of variable duration. The cycled CO2 adsorption and methanation were also investigated by in-situ DRIFT comparing results for xLi-Ru/Al2O3 materials against the reference Ru/Al2O3 catalyst. The favourable synergism existing at the nanoscale between the Li-aluminate sorbent phase and the catalytic Ru sites enhances the intrinsic activity of the DFMs that can guarantee high methane productivity and selectivity with low noble metal loadings.

Control and Impact of Metal Loading Heterogeneities at the Nanoscale on the Performance of Pt/Zeolite Y Catalysts for Alkane Hydroconversion.

The preparation of zeolite-based bifunctional catalysts with low noble metal loadings while maintaining optimal performance has been studied. We have deposited 0.03 to 1.0 wt % Pt on zeolite H-USY (Si/Al ∼ 30 at./at.) using either platinum(II) tetraammine nitrate (PTA, Pt(NH3)4(NO3)2) or hexachloroplatinic(IV) acid (CPA, H2PtCl6·6H2O) and studied the nanoscale Pt loading heterogeneities and global hydroconversion performance of the resulting Pt/Y catalysts. Pt/Y samples prepared with PTA and a global Pt loading as low as 0.3 wt % Pt (nPt/nA = 0.08 mol/mol, where nPt is the number of Pt surface sites and nA is the number of acid sites) maintained catalytic performance during n-heptane (T = 210–350 °C, P = 10 bar) as well as n-hexadecane (T = 170–280 °C, P = 5 bar) hydroisomerization similar to a 1.0 wt % Pt sample. For Pt/Y catalysts prepared with CPA, a loading of 0.3 wt % Pt (nPt/nA = 0.08 mol/mol) sufficed for n-heptane hydroisomerization, whereas a detrimental effect on n-hexadecane hydroisomerization was observed, in particular undesired secondary cracking occurred to a significant extent. The differences between PTA and CPA are explained by differences in Pt loading per zeolite Y crystal (size ∼ 500 nm), shown from extensive transmission electron microscopy energy-dispersive X-ray spectroscopy experiments, whereby crystal-based nPt/nA ratios could be determined. From earlier studies, it is known that the Al content per crystal of USY varied tremendously and that PTA preferentially is deposited on crystals with higher Al content due to ion-exchange with zeolite protons. Here, we show that this preferential deposition of PTA on Al-rich crystals led to a more constant value of nPt/nA ratio from one zeolite crystal to another, which was beneficial for catalytic performance. Use of CPA led to a large variation of Pt loading independent of Al content, giving rise to larger variations of nPt/nA ratio from crystal to crystal that negatively affected the catalytic performance. This study thus shows the impact of local metal loading variations at the zeolite crystal scale (nanoscale) caused by different interactions of metal precursors with the zeolite, which are essential to design and synthesize optimal catalysts, in particular at low noble metal loadings.

The oxygen reduction reaction on palladium with low metal loadings: The effects of chlorides on the stability and activity towards hydrogen peroxide

Hydrogen peroxide is considered one of the most important commodity chemicals worldwide but its main production method, the anthraquinone process, poses serious logistical, environmental and safety challenges. Electrocatalytic synthesis through the reduction of molecular oxygen is a promising H2O2 production route. However, the reduction of molecular oxygen is kinetically hindered and stable electrocatalysts with a high activity and selectivity towards the 2-electron transfer reaction are needed. In this work, we evaluated the influence of chloride on catalysts with low palladium loadings on the ORR selectivity towards H2O2. We report the factors and dynamics that influence H2O2 production and highlight synthesis strategies to obtain close to 100% selectivity. By probing the electrode surface after various degradation cycles, we evaluate the role of adsorbing species and the catalysts oxidation states on the hydrogen peroxide selectivity. We systematically modified the catalyst synthesis using different Pd-precursors that were reduced and supported on high surface area graphene nanoribbons. Identical location transmission electron microscopy was used to probe catalyst dynamics during reaction and the activities and selectivities were measured by a rotating ring disk electrode. We probe the potential boundary conditions that lead to catalyst degradation during accelerated stress tests and potentiostatic polarisation and demonstrate how the catalytically active surface can be revived after degradation. The obtained insights can be used as guideline for the development of active, selective and stable catalysts with low noble metal loadings.

Electrochemically Modifying the Electronic Structure of IrO2 Nanoparticles for Overall Electrochemical Water Splitting with Extensive Adaptability

AbstractDesigning the electrocatalysts that are stable and active for extensively adaptable water splitting is highly desirable for developing hydrogen based energy. IrO2 is a promising and widely used catalyst for the oxygen evolution reaction in commercial applications, but is rarely used for the hydrogen evolution reaction (HER), due to the high Gibbs free energy for hydrogen adsorption (ΔGH*). Herein, an approach to modify the electronic structure of IrO2 via cyclic voltammetry is proposed. In this process, Ir(+4) is partially reduced and trace Pt is simultaneously deposited on IrO2, which greatly lowers the ΔGH* and thus accelerates the reaction kinetics. The as‐prepared Pt–IrO2/CC with low noble metal loading (36.6 µg cm−2(Ir+Pt)) exhibits excellent HER activity with overpotentials of 5, 22, and 26 mV at 10 mA cm−2 in 0.5 m H2SO4, 1 m KOH, and 1 m phosphate buffer solution, respectively, making it possible to organize an all‐IrO2 based water electrolyzer. The Pt–IrO2/CC||IrO2/CC couple exhibits a promising activity and stability in pH‐universal conditions as well as natural seawater for H2 production. Density function theory calculations reveal that the optimized electronic structure of IrO2 balances the ΔGH*, resulting in a much enhanced HER performance.

Three-dimensional carbon foam supported MnO2/Pt for rapid capture and catalytic oxidation of formaldehyde at room temperature

Catalytic oxidation of formaldehyde (HCHO) at room temperature is one of the most viable approaches to indoor HCHO pollution abatement. Herein, three-dimensional (3D) carbon foam decorated with Pt/MnO2 nanosheets (Pt/MnO2-CF) was in-situ synthesized for room-temperature catalytic oxidation of HCHO. The 3D Pt/MnO2-CF with a low platinum content of 0.3 wt% exhibited excellent catalytic activity because of its hierarchically porous structure facilitating the diffusion of reactant molecules. Moreover, an abundance of active oxygen species resulting from oxygen vacancies are favorable for HCHO oxidation. In addition, the carbon foam substrate exhibited a very good HCHO adsorption capability, which helps achieve prompt reduction in HCHO concentration in the gas-phase and subsequent complete oxidation of adsorbed HCHO. The combination of adsorption and oxidation was more favorable for oxidative decomposition of HCHO. This work demonstrates that such 3D nanocomposites with low noble metal loading have promising application for indoor HCHO removal and air purification.

Highly dispersed Pd/modified-Al2O3 catalyst on complete oxidation of toluene: Role of basic sites and mechanism insight

Noble metal catalysts face high cost and limited resources challenge. Developing a high efficiency catalyst with low noble metal loading is an important way to meet this challenge. In this study, Mg-, Ba- and Zr-doped Pd/Al2O3 catalysts with Pd loading of 0.5 wt% were prepared by stepwise wet impregnation method and used for complete oxidation of toluene. These catalysts were characterized by powder X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), CO chemisorption, hydrogen temperature-programmed reduction (H2-TPR), temperature-programmed desorption of CO2 (CO2-TPD) and temperature-programmed desorption of oxygen (O2-TPD). Catalytic reaction of toluene and isopropyl alcohol were carried out in a fixed bed micro-reactor under the condition of GHSV = 24,000 ml h−1gcat−1 with 500 ppm toluene or isopropyl alcohol. The results of XRD, Raman and XPS revealed that PdO is the major species in all of the catalysts. The size of PdO remarkably decreased on MgO-doped Al2O3 surface. The results of H2 temperature-programmed reduction and O2 temperature-programmed desorption indicated that the reducibility of PdO and the active oxygen species were enhanced by doping basic element. In situ diffusion reflectance-infrared Fourier transform spectroscopy proved that benzaldehyde and carboxylates were the intermediate products of toluene oxidation. The results of X-ray photoelectron spectroscopy on used catalysts demonstrated that many more Pd2+ species were detected in Pd/MgO-Al2O3 sample, suggesting that a Pd2+/Pd0 pairs was formed which is favored to the combustion of toluene. The results show that the catalytic performance of Pd/Al2O3 was promoted by modifying basic oxides in the order of Pd/MgO-Al2O3 > Pd/BaO-Al2O3 > Pd/ZrO2-Al2O3 > Pd/Al2O3. The catalytic activity of 0.5 wt% Pd/MgO (2.0 wt%)-Al2O3 was similar with that of 1.0 wt% Pd/Al2O3.

Effective catalytic abatement of indoor formaldehyde at room temperature over TS-1 supported platinum with relatively low content

Abstract The catalytic removal of HCHO with low noble-metal loading at room temperature is meaningful and challenging work. Herein, high performance catalysts xPt/TS-1 (Si/Ti = 30, x = 0.1, 0.3, and 0.6 wt%) for HCHO oxidation were synthesized by polyvinyl alcohol-protected NaBH4 reduction method. The Pt/TS-1 sample loading with 0.3 wt% Pt nanoparticles (NPs) could completely remove 120 ppm HCHO at space velocity (SV) of 60,000 mL/(g h) at 20 °C. Moreover, the 0.3Pt/TS-1 sample remained outstanding activity and stability in humid air with 35–75% water vapor and at high SV with a range between 60,000 and 240,000 mL/(g h). Based on the results of UV–vis, Raman, NH3-TPD, Contact angle measurement, CO chemisorption, and O2-TPD, the excellent catalytic performance of Pt/TS-1 was mostly attributed to high Pt dispersion and high concentration of adsorbed oxygen species. This work expands the field of utilization of zeolite supported noble-metal catalysts for the purification of indoor pollutants.

Development of Supported Iridium Oxides As the Low Noble Metal Loading Anode for PEM Water Electrolyser

Reducing the cost of PEM water electrolyser is still a big challenge for renewable energy storage. Though there are some reports which have achieved very low Ir loading (0.1~0.2mg/cm2) in membrane electrode assemblies (MEA) for PEM water electrolyser, the other issues such as the performance and stability of MEA, the reduction of Pt loading in cathode and the scalability of preparation method of MEA still need further investigation for developing low cost and high performance PEM water electrolyser. In this work, to develop high performance anode with low Ir loading, highly active Iridium oxohydroxides were supported on conductive titanium metal nanosphere as the anode catalyst. The diatmeter of metal Ti nanosphere ranges from 60-200nm, and the Iridium oxohydroxides loaded on Ti support shows a particle size between 1.5-3nm. The OER activity of the catalyst with various Ir loading was characterized, and the catalyst with 10% Ir loading exhibited highest Ir mass activity (1700A/g @η=0.37V), it is about 6 times as the commercial IrO2. Increasing the loading of Ir will lead to the decline of Ir mass activity, this may be due to the limited surface area of Ti nanosphere. The stability of the catalyst (Ir loading 10%) was characterized by CV scans between 0.4-1.5V (vs.RHE) in 0.5M H2SO4. After 2000 cycles, the active sites of IrOx declined only 18%, and the catalyst does not show an obviously rising in resistance from EIS characterization, indicating a good stability both on active sites and support. The MEAs using such IrOx/Ti as the anode were prepared by conventional CCM method, and the Pt loading (20% wt. Pt/C) in cathode was reduced to about 0.2mg/cm2. The anode with various Ir loading and membrane with different thickness were determined at atmosphere under 80 degrees. The electrolyser with Ir loading 0.13mg/cm2 in anode, Pt loading 0.18mg/cm2 in cathode and N212 membrane achieved 1.623V at 1A/cm2 and 1.778V at 2A/cm2, which exhibits a good performance with such low noble metal loading. Further decreasing the Ir loading in anode catalyst layer will lead to performance degradation, but the rising of voltage was only 50-60mv at 1A/cm2 when Ir was reduced to 0.08 mg/cm2. With respect of the durability of MEAs, an electrolyser using Nafion 117 as the membrane, and 0.08 mg /cm2 Ir in MEA was tested under 1A/cm2. After 850h, the voltage increased from 1.79V to 1.83V, and the degradation rate is below 50μV/h, this suggests a good stability of supported Iridium oxohydroxides, and the stability of electrolyser with N212 membrane is now ongoing. Figure 1

Novel approach to immobilize Au nanoclusters on micro/nanostructured carbonized natural lotus leaf as green catalyst with highly efficient catalytic activity

To achieve high catalytic activity and stability with low noble-metal loadings on green and natural supports has attracted tremendous attention in the past few years. Herein, a facile strategy is exploited to synthesize Au nanoclusters (with size of ∼1.4 nm) which are homogeneously distributed on carbonized natural lotus leaf sheets with less mass. Compared to the pure AuNCs, the AuNCs@carbonized lotus leaf (AuNCs@C-lotus leaf) micro/nanohybrid with the unique papillae structures and large surface area not only exhibits better catalytic activity for the reduction of 4-nitrophenol (4-NP), but also prevent the aggregation of AuNCs. In addition, the catalytic performance of AuNCs@C-lotus leaf catalyst increased with the temperature increasing of the reaction temperature. Moreover, the AuNCs@C-lotus leaf catalyst can be packed into a filtering platform to fabricate a fixed-bed system, with which the catalytic conversion could reach 71.7% for 0.2 mM 4-NP solution that pass through at flow rate of 1 mL/min. Furthermore, the AuNCs@C-lotus leaf catalyst shows excellent recyclability and only slight loss of catalytical activity is observed after recycling for five successive times. This mild and environmental friendly methodology could be generalized to the synthesis of other metallic nanoparticles@carbonized botanical leaf micro/nanohybrids as promising heterogeneous catalysts for varied catalytic reactions.

Effect of Electronic Conductivities of Iridium Oxide/Doped SnO2 Oxygen-Evolving Catalysts on the Polarization Properties in Proton Exchange Membrane Water Electrolysis

We have developed IrOx/M-SnO2 (M = Nb, Ta, and Sb) anode catalysts, IrOx nanoparticles uniformly dispersed on M-SnO2 supports with fused-aggregate structures, which make it possible to evolve oxygen efficiently, even with a reduced amount of noble metal (Ir) in proton exchange membrane water electrolysis. Polarization properties of IrOx/M-SnO2 catalysts for the oxygen evolution reaction (OER) were examined at 80 °C in both 0.1 M HClO4 solution (half cell) and a single cell with a Nafion® membrane (thickness = 50 μm). While all catalysts exhibited similar OER activities in the half cell, the cell potential (Ecell) of the single cell was found to decrease with the increasing apparent conductivities (σapp, catalyst) of these catalysts: an Ecell of 1.61 V (voltage efficiency of 92%) at 1 A cm−2 was achieved in a single cell by the use of an IrOx/Sb-SnO2 anode (highest σapp, catalyst) with a low Ir-metal loading of 0.11 mg cm−2 and Pt supported on graphitized carbon black (Pt/GCB) as the cathode with 0.35 mg cm−2 of Pt loading. In addition to the reduction of the ohmic loss in the anode catalyst layer, the increased electronic conductivity contributed to decreasing the OER overpotential due to the effective utilization of the IrOx nanocatalysts on the M-SnO2 supports, which is an essential factor in improving the performance with low noble metal loadings.

Nanoporous water oxidation electrodes with a low loading of laser-deposited Ru/C exhibit enhanced corrosion stability.

For the oxidation of water to dioxygen, oxide-covered ruthenium metal is known as the most efficient catalyst, however, with limited stability. Herein, we present a strategy for incorporating a Ru/C composite onto a novel nanoporous electrode surface with low noble metal loading and improved stability. The Ru/C is coated on the pore walls of anodic alumina templates in a one-step laser-induced deposition method from Ru3(CO)12 solutions. Scanning electron microscopy proves the presence of a continuous Ru/C layer along the inner pore walls. The amorphous material consists of metallic Ru incorporated in a carbonaceous C matrix as shown by X-ray diffraction combined with Raman and X-ray photoelectron spectroscopies. These porous electrodes reveal enhanced stability during water oxidation as compared to planar samples at pH 4. Finally, their electrocatalytic performance depends on the geometric parameters and is optimized with 13 μm pore length, which yields 2.6 mA cm−2, or 49 A g−1, at η = 0.20 V.

Carbon-templated conductive oxide supports for oxygen evolution catalysis.

We present a novel route for the preparation of supported IrO2 catalysts for the oxygen evolution reaction in proton exchange membrane electrolyzers. It uses carbon soot as a nanostructure template, which is sequentially coated with a conductive niobium-doped titanium oxide (NTO) layer and an ultrathin, highly pure IrO2 catalyst layer by atomic layer deposition (ALD). The NTO acts as an oxidation-stable conductor between the metal current distributor and the catalyst. The highly controlled film growth by ALD enables the fabrication of electrodes with a very low noble metal loading. Nonetheless, these electrodes exhibit very high catalytic activity and good stability under cyclic and constant load conditions. At an IrO2 content of less than 10 percent by mass of the oxide material and an area-based Ir content of 153 μg cm-2, the nanostructured NTO/IrO2 electrode achieves an oxygen evolution current density of 1 mA cm-2 at an overpotential of ∼250 mV, which is significantly lower than the reported values for particulate NTO/IrO2 catalysts.

The electrochemical activity of two binary alloy catalysts toward oxygen reduction reaction in 0.1 M KOH

The platinum group metals (Pt, Ir and Ru) and the carbide-derived carbon support with the very high specific surface area were used to synthesise the low noble metal loading Pt-C, IrPt-C and RuPt-C alloy catalysts. The alloying of the platinum group metals in the studied catalysts was proved by the several independent physical characterization methods like: the X-ray diffraction, time of flight secondary ion mass-spectrometry, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy. The electrocatalytic activity toward oxygen reduction reaction of the synthesised catalysts in an alkaline solution was studied and compared with the commercially available Pt-Vulcan. The combined and detail approach using the transmission electron microscopy and inductively coupled plasma mass spectrometry for estimation of the surface area of metal particles is provided. The noticeably higher calculated mass corrected and specific kinetic current density values for Pt-C catalyst were established. For IrPt-C and RuPt-C alloy catalysts, mass corrected current density values are comparable with the commercial Pt-Vulcan. The specific kinetic current density values increase in the following sequence: RuPt-C < IrPt-C < Pt-Vulcan < Pt-C.

Graphene-doped electrospun nanofiber membrane electrodes and proton exchange membrane fuel cell performance

Abstract A rational electrode structure can allow proton exchange membrane (PEM) fuel cells own high performance with a low noble metal loading and an optimal transport pathway for reaction species. In this study, we develop a graphene doped polyacrylonitile (PAN)/polyvinylident fluoride (PVDF) (GPP) electrospun nanofiber electrode with improved electrical conductivity and high porosity, which could enhance the triple reaction boundary and promote gas and water transport throughout the porous electrode. Thus the increased electrochemical active surface area (ECSA) of Pt catalysts and fuel cell performance can be expected. As results, the ECSA of hot-pressed electrospun electrodes with 2 wt% graphene oxide (GO) is up to 84.3 m 2 /g, which is greatly larger than that of the conventional electrode (59.5 m 2 /g). Significantly, the GPP nanofiber electrospun electrode with Pt loading of 0.2 mg/cm 2 exhibits higher fuel cell voltage output and stability than the conventional electrode.

A comparative study of the H2-assisted selective catalytic reduction of nitric oxide by propene over noble metal (Pt, Pd, Ir)/γ-Al2O3 catalysts

The impact of H2 as additional reducing agent on the SCR of NO with C3H6 in excess oxygen, was comparatively explored over low noble metal loading (0.5wt%), Pt/γ-Al2O3, Pd/γ-Al2O3, Ir/γ-Al2O3 catalysts. To gain insight into the role of H2, the reactions NO+C3H6+O2 (R#1), NO+C3H6+O2+H2 (R#2), NO+H2+O2 (R#3) were employed. In respect to propene oxidation, the Pd>Pt>Ir sequence was obtained under R#1, since they exhibit complete conversion at 220, 250, 325°C, respectively; all metals exhibit moderate deNOx performances (XNO, <40%). H2 co-presence (R#2) promotes both the NO and C3H6 conversions, which is valid in the whole temperature interval investigated (50–400°C), being more substantial for Pt/γ-Al2O3 and Ir/γ-Al2O3, less beneficial for Pd/γ-Al2O3. A two-maxima feature is obtained on XNO pattern (at ∼100 and ∼230°C) of Pt and Pd during R#2. The low temperature maximum −attributed to NO reduction by H2- is substantially more pronounced on Pt than Pd, offering XNO ∼90% and SN2 ∼85%; the high temperature maximum—attributed to NO reduction by C3H6—is higher by ∼15% on both Pt and Pd, in respect to the values obtained during R#1, while SN2 remained unaffected. Different XNO pattern with one maximum is obtained over Ir, implying a synergistic interaction between H2 and C3H6. This synergy is accompanied by a substantial widening of the NO reduction window toward lower temperatures and a considerable increase on both XNO,max and SN2 (from XNO ∼30% with SN2 ∼55% during R#1 to XNO ∼70% with SN2 ∼95% during R#2). The specific features of all reactions and metals employed are comparatively discussed.

Generation and Properties of Brønsted Acid Sites in Bifunctional Rh-, Ir-, Pd-, and Pt-Containing Zeolites Y Investigated by Solid-State NMR Spectroscopy

In the present work, the generation and properties of Bronsted acidic bridging OH groups (Si(OH)Al) in Rh-, Ir-, Pd-, and Pt-containing zeolites Y were quantitatively investigated by multinuclear solid-state NMR spectroscopy. The number of Si(OH)Al groups formed per noble metal atom upon their reduction was found to be 0.3 to 1.3 instead of the theoretically expected values of 2 (Pd2+, Pt2+) or 3 (Rh3+, Ir3+). For zeolites Y with low noble metal loadings, a significantly lower acid strength of Si(OH)Al groups in comparison with those of H,Na–Y zeolites occurred. Interestingly, noble metal-containing zeolites Y with lower acid strength have a significant content of not completely reduced noble metal atoms with partially cationic character. The spatial distribution of Si(OH)Al groups in noble metal-containing zeolites Y was found to differ significantly from that in H,Na–Y zeolites. This effect is explained by the migration of a significant content of noble metal atoms into the sodalite cages of zeolites Y ...

PtCo catalyst with modulated surface characteristics for the cathode of direct methanol fuel cells

A PtCo catalyst with an ordered cubic primitive structure was synthesized and investigated for the application as a cathode in direct methanol fuel cells. The synthesis involved the preparation of an amorphous PtOx/C precursor by the sulfite complex route, an impregnation with Co(NO3)2, a high temperature (800 °C) carbothermal reduction and, finally, a leaching procedure. This method led to the occurrence of a Pt3Co/C catalyst with a primitive cubic ordered (L12) phase and a mean crystallite size of 3.3 nm, as well as a suitable degree of alloying. This electrocatalyst was investigated for the oxygen reduction reaction in a direct methanol fuel cell (DMFC) operating in the range 30–90 °C. At 60 °C, under atmospheric pressure, a maximum power density of 40 mW cm−2 was obtained with the new PtCo catalyst formulation at low noble metal loading on the electrode (1 mg cm−2). This performance was 2.3 times higher than a benchmark Pt catalyst used for comparison.

Membrane electrode assemblies with low noble metal loadings for hydrogen production from solid polymer electrolyte water electrolysis

High performance membrane electrode assemblies (MEAs) with low noble metal loadings (NMLs) were developed for solid polymer electrolyte (SPE) water electrolysis. The electrochemical and physical characterization of the MEAs was performed by I–V curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Even though the total NML was lowered to 0.38 mg cm−2, it still reached a high performance of 1.633 V at 2 A cm−2 and 80 °C, with IrO2 as anode catalyst. The influences of the ionomer content in the anode catalyst layer (CL) and the cell temperature were investigated with the purpose of optimizing the performance. SEM and EIS measurements revealed that the MEA with low NML has very thin porous cathode and anode CLs that get intimate contact with the electrolyte membrane, which makes a reduced mass transport limitation and lower ohmic resistance of the MEA. A short-term water electrolysis operation at 1 A cm−2 showed that the MEA has good stability: the cell voltage maintained at ∼1.60 V without distinct degradation after 122 h operation at 80 °C and atmospheric pressure.

Electrocatalysts: PdAg Nanorings Supported on Graphene Nanosheets: Highly Methanol‐Tolerant Cathode Electrocatalyst for Alkaline Fuel Cells (Adv. Funct. Mater. 10/2013)

On page 1289, Wei Chen and co-workers report a method to fabricate graphene-supported PdAg nanorings. As a potential fuel cell electrocatalyst, the hybrid nanomaterial exhibits excellent catalytic performance for oxygen reduction with the clean product of water. The unique nanostructure of the material with large active surface area, low noble metal loading, and high methanol tolerance is highlighted.

Mesoporous carbon supported nanoparticulated PdNi 2: A methanol tolerant oxygen reduction electrocatalyst

The kinetics of the oxygen reduction reaction (ORR) of PdNi 2 nanoparticles supported on a high specific area mesoporous carbon (MC) and Vulcan carbon was studied in the presence and absence of methanol in acid media. The electrocatalysts, synthesized by chemical reduction of the metal chlorides with NaBH 4 in aqueous media were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The catalyst supported on MC has a higher degree of Ni alloying and a smaller particle size than that supported on Vulcan. The electrochemical characterizations by RDE and DEMS indicate that PdNi 2 supported on the high surface area MC exhibits higher catalytic activity for the ORR, very similar to that of Pd- and Pt-based alloys with the advantage of a very low noble metal loading. Moreover, the PdNi 2 supported on MC shows an excellent methanol tolerance in acid media. Thus, this novel combination catalyst/support would be a suitable cathodic catalyst for direct methanol fuel cells.