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This work reports on the synthesis and characterization of hybrid electrocatalysts based on Pt nanoparticles and ceria nanorods (CeO2 NR) supported on Vulcan XC‐72 carbon black (Ptx(CeO2 NR)yCz) and evaluation of their electrocatalytic activity towards the oxygen reduction reaction (ORR), aiming the application of 4‐electrons process in direct ethanol fuel cells (DEFCs). The hybrid electrocatalysts are characterized by X‐ray diffraction (XRD), energy‐dispersive spectroscopy (EDS), transmission electron microscopy (TEM), contact angle measurements and X‐ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP‐MS), CO‐stripping analysis and electrocatalytic activity for ORR studied by the rotating ring‐disc electrode (RRDE) technique and single fuel cell experiments. The Ptx(CeO2 NR)yCz hybrid electrocatalysts prove to be efficient for ORR in a 4‐electron process, maintaining a high conversion rate of O2 to H2O, even at reduced platinum (Pt) load. The electrocatalyst presents a notable an unusual behavior in single fuel cell experiments presenting slightly lower open circuit voltage than Pt based commercial electrocatalysts, containing Pt only, as well as improved current and power density. This is achieved at operating temperatures between 40 °C and 70 °C, making the material very promising for application in high efficiency low temperature fuel cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Iron nitrate enhances adsorption capacity of cotton, activates carbon pores and develop magnetic specie in carbon. • A green method of simultaneous carbonization, activation and magnetization. • Magnetism enhances ethanol oxidation in 5.6 times compared to Pd/AlfaAesar catalyst. • Better dispersion of Pd nanoparticles due to high micro porosity of cotton carbon. Activate carbon (AC) demand has increased worldwide, with application in adsorption, heterogeneous catalysis, and most recently as electrocatalyst support. However, while AC production from agro-industrial waste are widely researched, textile waste is neglected as raw material. In this study, cotton fabric was first applied as textile dye adsorbent after iron impregnation, which enhanced the adsorption capacity. The dye adsorbed fabric was than sequentially pyrolyzed at 800 °C for 2 h under N 2 atmosphere, producing a magnetic mesoporous activated carbon (MAC) of 472 m2 g-1 BET surface area with 82% micropores and magnetization saturation of 34.2 emu g-1 deriving from encapsulated metallic αFe. This new simple and fast one-step carbonization, activation and iron incorporation method, has very low chemicals consumption and waste generation compared to the traditionally applied ones. The so produced MAC was loaded with 20 % Pd and tested for electrocatalyst properties: high density current for ethanol oxidation of 549 mA mg-1Pd, 1.37 times higher than using commercial Pd catalyst, lower onset potential of -0.48 V vs NHE. Application of the electrocatalyst for direct ethanol fuel cell achieved a high energy production of 27 mW cm-2 at 353 K. [ABSTRACT FROM AUTHOR]

This study demonstrates the structural properties and evaluates the electrocatalytic activity of an ethanol oxidation reaction using ternary materials composed by Pd and Sn nanoparticles combined with CeO 2 nanorods (NR) anchored on Vulcan carbon black to be used as an anode in alkaline direct ethanol fuel cells (ADEFCs). The highest open circuit voltage (1010 mV), maximum power (30 mW cm−2) and current densities (113 mA cm−2) were achieved using (Pd 1 Sn 3) 10 (CeO 2 NR) 20 (Vn) 70 , while the commercial anode values were 968 mV, 23 mW cm−2 and 123 mA cm−2. Although similar performance for both anodes was observed, the ternary hybrid electrocatalyst contains an 8-fold lower Pd content than the commercial material. This outcome may be justified by the higher defect density presented by the carbon support observed by Raman spectroscopy and the metal oxidation state modifications detected by X-ray photoelectron spectroscopy, as well as the electrochemically active surface area presented by the ternary electrocatalyst. The combination of higher vacancies, defects and oxygenated species in the carbon support and the synergistic effect between the oxyphilic Sn and CeO 2 NR species and the Pd nanoparticles results in an electrochemical performance that makes these ternary electrocatalysts promising anode materials for ADEFC applications. [Display omitted] • Ternary electrocatalysts based on Pd 1 Sn 3 nanoparticles and CeO 2 nanorods for EOR. • Ternary electrocatalysts with better performance in ADEFC tests. • Synergic effect, defects, oxygenated species and vacancies are important for the EOR. [ABSTRACT FROM AUTHOR]

Fossil fuel alternatives are being increasingly studied, and alkaline direct ethanol fuel cells (ADEFC) have acquired importance, as to ethanol is a renewable fuel. In this context, the aims of the present study were to synthesize, characterize and evaluate electrocatalytic activity in oxygen reduction reaction (ORR) and ethanol oxidation reaction (EOR) using hybrid electrocatalysts based on Pd nanoparticles and CeO 2 nanorods supported on carbon black for application in ADEFC. The highest OCV, maximum current and power densities obtained using Pd 15 (CeO 2 NR) 10 (Vn) 75 as the cathode and Pd 10 (CeO 2 NR) 20 (Vn) 70 as the anode were 1270 mV, 190 mA cm−2 and 65 mW cm−2, respectively. These interesting results are justified by the highest I D /I G ratio and ECSA, which suggest a high number of oxygenated species, defects and vacancies in these electrocatalysts and by the synergistic effect between CeO 2 NR and Pd nanoparticles. Therefore, these hybrid electrocatalysts are promising for ADEFC applications. [Display omitted] • Hybrid electrocatalysts based on Pd and Ceria nanorods for EOR and ORR. • The electrocatalysts were applied as cathode and anode in ADEFC experiments. • Better performance compared to commercial materials in ADEFC tests. • Oxygenated species, vacancies and defects are the main electrocatalytic effects. [ABSTRACT FROM AUTHOR]

In this work electrocatalysts based on Pd and Sn nanoparticles supported on Vulcan XC-72 carbon black with a reduced amount of Pd were prepared. We evaluated its electrocatalytic activity for ethanol oxidation reaction (EOR) in alkaline direct ethanol fuel cells (ADEFCs). The electrocatalysts were synthesized in different Pd:Sn mass ratios (1:3, 1:1, 3:1 and 1:0) on the carbon containing 20 wt % of metal. The XRD patterns of the electrocatalysts revealed an alloy formation between Pd and Sn, and the electrocatalysts with lowest amount of Pd (Pd1Sn3/Vulcan XC-72) and highest electrochemically active surface area (ECSA) presented best performance in ADEFC experiments with a maximum current density and power density of 152 mA cm-2 and 42 mW cm-2, respectively. Besides the current density three times higher for EOR than that of the pure Pd, the open circuit potential of 939 mV at an operation temperature of 80 °C yielded the higher carbonate production. This behavior can be attributed to the presence of oxophilic Sn species, which improve the ability to remove adsorbed CO. Oxygenated species, vacancies and defects detected in the structure of PdxSny/Vulcan XC-72 catalysts are accounted for their high activity, making them very promising for the application in ADEFC. • Pd 1 Sn 3 /Vulcan XC-72 showed the highest power density (42 mW cm−2 at 80 °C). • The cell with Pd 1 Sn 3 /Vulcan XC-72 showed an open circuit potential of 939 mV. • KOH concentration effect study a power density of 42 mW cm−2 was obtained. • The good performance can be justified by the higher carbonate formation. [ABSTRACT FROM AUTHOR]

Pd 1 Nb 1 /C on different kinds of carbon black were prepared by a modified sol-gel method. The alkaline direct ethanol fuel cell (ADEFC) performance was performed first with the Pd 1 Nb 1 electrocatalysts and then by varying the fuel concentration. In CV, Pd 1 Nb 1 /Printex 6L (50:50 wt%) exhibited 2.2 times higher mass activity than that of the Pd/C (Alfa Aesar); their mass activities were 1300 and 590 mA mg Pd − 1 , respectively. The best performance for the ADEFC was obtained using Pd 1 Nb 1 /Printex 6L, which yielded a maximum power density and cell voltage of 28 mW cm−2 and 1.17 V, respectively. The Pd 1 Nb 1 /Printex 6L electrocatalyst exhibited a more negative onset potential for the CO stripping reaction. We suggest that the higher hydrophilicity (contact angle) and higher degree of disorder of Printex 6L (Raman) corroborates these results. In addition, both bifunctional and electronic effects operated on the electrocatalyst due to the presence of metal oxides and alloys of PdNb (XRD), respectively, in the synthesized electrocatalysts. Therefore, it was notable that the support has an essential role—as important as the cocatalyst—in the electrocatalytic performance. ● Pd1Nb1/C binary electrocatalysts supported on different carbon black to ADEFC. ● Pd1Nb1/Printex 6L exhibited 2.2 times higher activity compared to Pd/C (Alfa Aesar©). ● The best performance for the ADEFC was obtained using Pd1Nb1/Printex 6L. ● This performance indicates an excellent energy efficiency of approximately 92%. ● The Printex 6L showed here as the best support than other carbon blacks. [ABSTRACT FROM AUTHOR]

PtSnNi electrocatalysts (60: 40: 40 mass ratio) supported on Vulcan® XC-72 (Cabot) carbon and COOH-functionalized multiwalled carbon nanotubes (Cheaptubes®) with 15% of metal loading were prepared. The nanoparticles size of 2–3 nm for both supports was estimated by HRTEM. In the direct ethanol fuel cell experiments, PtSnNi/C presents 50 mA cm−2 reaching the maximum power density (MPD) of 12 mW cm−2 and decreasing at higher currents, while PtSnNi/MWCNT-COOH obtains similar values of MPD (60 mA cm−2), but keeping the best performance. By GC (gas chromatography) technique, it was possible to observe that the electrocatalyst supported on MWCNT-COOH favored the ethanol oxidation to acetaldehyde and acetic acid, although the material supported on Vulcan® XC-72 carbon presented almost 100% of selectivity for acetaldehyde. This behavior was maintained also when the current of 0.1 A was applied for 80 min. For the PtSnNi/C electrocatalyst, the selectivity to only acetaldehyde can be related to Sn and Ni dissolution process that can become the electrocatalytic activity similar to Pt/C, decreasing the power density as observed in our experiments. Established by EDS analysis, after 80 min of polarization, the Ni and Sn relative atomic ratio was lower on the catalytic anodic layer of PtSnNi/C than on PtSnNi/MWCNT-COOH. Image 1 • The MWCNT-COOH support originated species for ethanol oxidation reaction. • PtSnNi/MWCNT-COOH presented greatest activity with good chemical stability. • PtSnNi/MWCNT-COOH selectively produces acetic acid and acetaldehyde. [ABSTRACT FROM AUTHOR]

Fuel cells are important energy conversion devices. However, challenges in this regard are still noted, such as low electrocatalyst efficiencies in the oxygen reduction reaction (ORR), which occurs slowly in electrocatalyst cathodes. In this sense, this study aimed to synthetize hybrid binary and ternary electrocatalysts formed by palladium and platinum alloy nanoparticles and ceria nanorods (CeO 2 NR) supported on carbon black Vulcan XC-72 (Pd x Pt y /Vn and (Pd 3 Pt 1) x (CeO 2 NR) y (Vn) z) for the study of the oxygen reduction reaction (ORR) and application as alkaline direct ethanol fuel cells (ADEFCs) cathodes. The binary and ternary hybrid electrocatalysts were characterized using different physicochemical and electrochemical techniques. The ternary hybrid electrocatalyst, (Pd 3 Pt 1) 15 (CeO 2 NR) 10 (Vn) 75 , reached higher open circuit voltage (OCV), maximum current and power densities, of 1.13 V, 219 mA cm-2 and 61 mW cm-2, respectively, compared to the commercial Pt/C Alfa Aesar (AA) and other evaluated electrocatalysts. The ternary hybrid electrocatalyst, (Pd 3 Pt 1) 15 (CeO 2 NR) 10 (Vn) 75 , is interesting for application as an ADEFC cathode targeting the ORR, due to an almost 3-fold maximum power density and almost twice the maximum current density compared to a commercial electrocatalyst with the same noble metal loading, explained by increased defects and oxygenated species in this electrocatalyst as revealed by Fourier Transform Infrared Spectroscopy (FT-IR) and Raman analyses. [Display omitted] • PdPtCeO 2 nanorods for oxygen reduction reaction. • Oxygenated species, vacancies and defects are the main electrocatalytic effects for ORR. • Synergic effect was observed between Pd and Pt nanoparticles and ceria nanorods. • PdPtCeO 2 nanorods with better performance in alkaline direct ethanol fuel cell tests. [ABSTRACT FROM AUTHOR]

NaNbO 3 microcubes with Pd for application in an Alkaline Direct Ethanol Fuel Cell (ADEFC) anode with high performance and minimal amounts of Pd are investigated herein. The Pd heterostructure on NaNbO 3 is evaluated in two different structures NaNbO 3 –Pd/C and NaNbO 3 @Pd/C. NaNbO 3 –Pd/C electrocatalyst presents a less positive E onset for CO-stripping. The NaNbO 3 –Pd/C electrocatalyst exhibits lower Pd and Nb mass losses compared to NaNbO 3 @Pd/C during the 24-h experiment. A single ADEFC experiment has 18 mW cm−2 at 50 and 60 °C using only 0.16 mg cm−2 of Pd for NaNbO 3 –Pd/C production. This Pd metallic loading is 6-fold lower than that of commercial Pd/C (AA). Experimental evidence indicates that the electronic effect between Pd and Nb and the high EASA are the likely reasons for these findings. Therefore, NaNbO 3 microcubes with Pd may be an advantageous electrocatalyst for applications in ADEFC anodes. [Display omitted] • NaNbO 3 microcubes decorated with Pd applied in Alkaline Direct Ethanol Fuel Cells. • Pd on NaNbO 3 were investigated using chemical reduction and galvanic substitution. • NaNbO 3 –Pd/C exhibited the lowest mass loss of Pd and Nb during 24 h of experiment. • Single ADEFC reached 18 mW cm−2 with only 0.16 mg cm−2 of Pd for NaNbO 3 –Pd/C. • Electronic effect between Pd and Nb and high EASA are the reasons for the results. [ABSTRACT FROM AUTHOR]