Formic acid electrooxidation on small, {100} structured, and Pd decorated carbon-supported Pt Nanoparticles

The use of shape-controlled nanomaterials represents an elegant way to improve the performance of many electrochemical reactions. However, two main aspects must be still optimised: decreasing particle size and increasing their activity. This study shows that the deposition of Pd on different small (3-5 nm) supported Pt materials (displaying a preferential structure containing ∼40% of Pt{100} terraces) leads to a great enhancement in the electrocatalytic activity towards the formic acid electrooxidation reaction. After Pd decoration, the oxidation takes place at lower overpotentials and oxidation current densities are significantly higher than those observed with all the bare Pt/C samples. For the Pt/C 45% catalyst, the intrinsic activity after Pd deposition was more than three times of that without Pd, while the oxidation overpotential shifted about ∼200 mV to lower overpotentials.This work was supported by the Ministerio de Ciencia e Innovación-FEDER (Spain) Project PID2019-105653GB-100 and Generalitat Valenciana (Project PROMETEO/2020/063). R.M.A and R.M.T thank to the support from FAPESP, Procs. 2019/08051-0, 2017/15469-5 and 15/26308-7. H.E. thanks the Estonian Research Council (grant No PUTJD841)

Small (<5 nm), Clean, and Well‐Structured Cubic Platinum Nanoparticles: Synthesis and Electrochemical Characterization

Shape‐controlled metal nanoparticles are significantly improving the electrocatalysis of many relevant reactions. By controlling the shape of nanoparticles, it is possible to engineer their surface to exhibit a preferential structure. However, to facilitate the incorporation of shaped nanomaterials into practical electrochemical devices, it is indispensable to overcome limitations caused by their large particle size (typically >5 nm). For practical applications, nanoparticles must have a size lower than 5 nm with a clean surface to decrease costs and provide a sufficiently large specific surface area. This is a major challenge that has remained unexplored up to now. Herein, we present the synthesis and electrochemical characterization of 3–5 nm, with well‐defined cubic Pt nanoparticles supported on carbon. The electrochemical characterization of the nanoparticles evidences the existence of a preferential {100} and clean structure (within about 40 % of {100} terrace surface).This paper was performed under Ministerio de Ciencia e Innovación-FEDER (Spain) Project PID2019-105653GB-100 and Generalitat Valenciana (Project PROMETEO/2020/063). J.S.G. thanks VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante (UATALENTO16-02). R.M.A and R.M.T thank to the support from FAPESP, Procs. 2019/08051-0, 2017/15469-5 and 15/26308-7. H.E. thanks the Estonian Research Council (grant No PUTJD841)

Improving the Electrocatalytic Activities and CO Tolerance of Pt NPs by Incorporating TiO2 Nanocubes onto Carbon Supports

Designing efficient anode CO-tolerant electrocatalysts is critical in low-temperature fuel cell catalysts fueled either by H-2/CO or alcohol. We demonstrate that the incorporation of TiO2 nanocubes (TiO2NCs) on Carbon Vulcan supports, followed by the synthesis of Pt NPs at their surface (Pt/TiO2NCs-C material), led to improvements in performance towards the electrooxidation of carbon monoxide, ethanol, methanol, ethylene glycol, and glycerol in acidic media relative to the commercial Pt/C and Pt/TiO2-C counterparts employing commercial TiO2. The nanocubes enabled changes in the electronic properties of Pt NPs while contributing to the bifunctional mechanism as compared to Pt/C and Pt/TiO2-C with commercial TiO2. Fuel cell experiments fed with H-2/CO steam showed that Pt/TiO2NCs-C employing nanocubes was resistant to CO-poisoning, yielding superior performance in operational conditions. The results reported herein have important implications for developing electrocatalysts with superior performances in PEMFCs.Peer reviewe

Oxygen electroreduction on small (<10 nm) and {100}-oriented Pt nanoparticles

Oxygen reduction reaction (ORR) was studied on {100}-oriented Pt nanoparticles with sizes 3 to 7 nm in sulphuric acid solution. The distribution and size of nanoparticles was analysed by transmission electron microscopy and metal loading was determined by inductively coupled plasma optical emission spectroscopy. The synthesised nanoparticles have about 40% of Pt(100) facet and 10% Pt(111) as determined from Ge and Bi adsorption, respectively. The four Pt/C catalysts with metal loading from 25 to 38 wt% were tested for ORR activity in 0.5 M H2SO4 solution using the rotating disk electrode method. It was found that the ORR proceeds mainly via a 4-electron pathway with the rate-limiting step being the transfer of the first electron to O2 molecule. The mass activities for ORR increase with decreasing the particle size, but specific activity and mass-specific activity have a maximum at 4.6 nm particle size. This means the most optimal {100}-oriented Pt size for ORR is around 4.6 nm in sulphuric acid solution.This paper was performed under Ministerio de Ciencia e Innovación-FEDER (Spain) Project PID2019-105653GB-100 and Generalitat Valenciana (Project PROMETEO/2020/063). R.M.A and R.M.T thank to the support from FAPESP, Procs. 2019/ 08051-0, 2017/15469-5 and 15/26308-7. H.E. thanks the Estonian Research Council (grant No PUTJD841). This research was also supported by the EU through the European Regional Development Fund (TK141 “Advanced materials and high-technology devices for energy recuperation systems”)

Palladium nanoparticles supported on mesoporous biocarbon from coconut shell for ethanol electro-oxidation in alkaline media

Abstract Palladium nanoparticles supported on carbon Vulcan XC72 (Pd/C) and biocarbon (Pd/BC) synthesized by sodium borohydride process were used as catalysts for ethanol electro-oxidation in alkaline media. The biocarbon (BC) from coconut shell with mesoporous and high surface area (792 m2 g−1) was obtained by carbonization at 900 °C and the hydrothermal treatment in a microwave oven. The D-band and G-band intensity ratio (I D/I G) from Raman analysis showed high disorder of the biocarbon, while X-ray photoelectron spectroscopy (XPS) suggests higher percentage of oxygen groups on the surface of biocarbon than of Vulcan XC72. From X-ray diffraction (XRD), it was observed peaks in 2θ degree related to the face centered cubic (fcc) structure of palladium and the mean crystallite sizes calculated based on the diffraction peak of Pd (220) were 5.6 nm for Pd/C and 5.3 nm for Pd/BC. Using Transmission Electron Microscope (TEM), it was observed particles well dispersed on both carbons support materials. The electrocatalytic activity of the materials was investigated by cyclic voltammetry (CV) and chronoamperometry (CA) experiments. The peak current density (on CV experiments) from ethanol electro-oxidation on Pd/BC was 50% higher than on Pd/C, while the current density measured at 15 min of CA experiments was 80% higher on Pd/BC than on Pd/C. The higher catalytic activity of Pd/BC might be related to the large surface area of the biocarbon (792 m2 g−1) vs (239 m2 g−1) of Vulcan carbon, the defects of the biocarbon structure and higher amount of oxygen on the surface than Carbon Vulcan XC 72

One-Step synthesis of PtFe/CeO2 catalyst for the Co-Preferential oxidation reaction at low temperatures

Active Pt-based catalysts at low temperature towards the preferential oxidation of carbon monoxide in hydrogen-rich stream reaction (CO-PROX) are of great importance for H-2-fueled fuel cells, but still remain a challenge. Herein, we propose a simple approach to synthesize a highly active Pt20Fe/CeO2 catalyst employing the borohydride reduction process. Transmission electronic microscopy revealed monodispersed 2.8 nm-Pt nanoparticles on CeO2, and the role of Fe species on the activity is discussed. The excellent CO conversion of 99.6% and CO2 selectivity of 92.3% carried out at ambient temperature meet the CO-PROX requirements for an adequate supply of hydrogen in fuel cell device. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Reconstruction of interactions in the ProtoDUNE-SP detector with Pandora

International audienceThe Pandora Software Development Kit and algorithm libraries provide pattern-recognition logic essential to the reconstruction of particle interactions in liquid argon time projection chamber detectors. Pandora is the primary event reconstruction software used at ProtoDUNE-SP, a prototype for the Deep Underground Neutrino Experiment far detector. ProtoDUNE-SP, located at CERN, is exposed to a charged-particle test beam. This paper gives an overview of the Pandora reconstruction algorithms and how they have been tailored for use at ProtoDUNE-SP. In complex events with numerous cosmic-ray and beam background particles, the simulated reconstruction and identification efficiency for triggered test-beam particles is above 80% for the majority of particle type and beam momentum combinations. Specifically, simulated 1 GeV/$c$ charged pions and protons are correctly reconstructed and identified with efficiencies of 86.1$\pm0.6$% and 84.1$\pm0.6$%, respectively. The efficiencies measured for test-beam data are shown to be within 5% of those predicted by the simulation

Supernova Pointing Capabilities of DUNE

International audienceThe determination of the direction of a stellar core collapse via its neutrino emission is crucial for the identification of the progenitor for a multimessenger follow-up. A highly effective method of reconstructing supernova directions within the Deep Underground Neutrino Experiment (DUNE) is introduced. The supernova neutrino pointing resolution is studied by simulating and reconstructing electron-neutrino charged-current absorption on $^{40}$Ar and elastic scattering of neutrinos on electrons. Procedures to reconstruct individual interactions, including a newly developed technique called ``brems flipping'', as well as the burst direction from an ensemble of interactions are described. Performance of the burst direction reconstruction is evaluated for supernovae happening at a distance of 10 kpc for a specific supernova burst flux model. The pointing resolution is found to be 3.4 degrees at 68% coverage for a perfect interaction-channel classification and a fiducial mass of 40 kton, and 6.6 degrees for a 10 kton fiducial mass respectively. Assuming a 4% rate of charged-current interactions being misidentified as elastic scattering, DUNE's burst pointing resolution is found to be 4.3 degrees (8.7 degrees) at 68% coverage