Comparing different nanoparticles’ protecting layers that can slow down the degradation of Pd-Ni based catalyst during Hydrogen Oxidation Reaction (HOR) in alkaline media

International audienc

Comparing different nanoparticles’ protecting layers that can slow down the degradation of Pd-Ni based catalyst during Hydrogen Oxidation Reaction (HOR) in alkaline media

International audienc

Bimetallic Pt or Pd-based carbon supported nanoparticles are more stable than their monometallic counterparts for application in membraneless alkaline fuel cell anodes

International audienceAlkaline fuel cells (AFCs) are relevant for niche applications, but still require enhanced performance and lifetime. Active and durable hydrogen oxidation reaction (HOR) catalysts must be developed: linking their electrochemical surface area (ECSA) loss to their HOR activity and understanding whether the ECSA loss of carbonsupported platinum group metal-based (PGM/C) HOR catalysts is irreversible (nanoparticles dissolution, detachment, Ostwald ripening) or reversible is pivotal. Using identical-location transmission electron micrographs (IL-TEM) and ECSA characterizations by "CO-like" stripping undertaken pre and post accelerated stress tests (AST), the different degradation mechanisms undergone by monometallic (Pt/C and Pd/C) and bimetallic catalysts (Pd-Pt/C and Pd-Ni/C) are unveiled. Monometallic PGM/C undergo extensive reversible poisoning and irreversible degradation upon operation at low potential, in contrast to bimetallic catalysts, which are less affected. Pd-Ni exhibits the smallest loss of ECSA PGM and HOR activity: it poorly catalyzes carbon corrosion and is hardly poisoned by "CO-like" species

Morphology and Doping Level of Electropolymerized Biselenophene-Flanked 3,4- Ethylenedioxythiophene Polymer: Effect of Solvents and Electrolytes

Biselenophene-flanked 3,4-ethylenedioxythiophene (EDOT) based polymer films were obtained by electrochemical polymerization. The effects of polymerization conditions such as supporting electrolytes and solvents on doping level, optical property and morphology of the polymer films were systematically studied. Interestingly, we found that polymer prepared by using different supporting electrolytes (TBAPF(6), TBABF(4) and TBACIO(4)) has significant effects on the doping level of the polymer films, whereas electropolymerized solvents (acetonitrile and dichloromethane) has no such effects on doping level. The polymer films show reversible dedoping and doping behavior upon treatment with hydrazine hydrate and iodine respectively. Biselenophene-flanked EDOT polymer shows a band gap of about 1.6 eV which is comparable to poly(3,4- ethylenedioxythiophene) (PEDOT) and parent polyselenophene, whereas finetuning of HOMO and LUMO energy levels has been found. In contrast, we observed that electropolymerized solvent has a major effect on morphology of the polymer films, while supporting electrolyte has very minor effects on the morphology. The surface morphologies of the polymer films were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM) techniques. We also present an efficient synthesis of bisthiophene-flanked bridged EDOT (ETTE), and biselenophene-flanked bridged EDOT (ESeSeE), and their electrochemical polymerization, characterizations and throughout comparison where applicable. A density functional theory (DFT) calculation of the corresponding polymers and a comparison with polythiophene (PT), polyselenophene (PSe), PEDOT and EDOT- based copolymers (PETE and PESeE) has been made