Effect of Sn Doping on Pd Electro-Catalysts for Enhanced Electro-Catalytic Activity towards Methanol and Ethanol Electro-Oxidation in Direct Alcohol Fuel Cells

Abstract

Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) method, using flaxseed oil as a carbon source. The alcohol reduction method was used to prepare Pd/CNOs and Pd-Sn/CNOs electro-catalysts, with ethylene glycol as the solvent and reduction agent. The metal-nanoparticles were supported on the CNO surface without adjusting the pH of the solution. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with concentric graphite ring morphology, and also PdSn nanoparticles supported on the CNOs. X-ray diffractometry (XRD) patterns confirm that CNOs are amorphous and show the characteristic diffraction peaks of Pd. There is a shifting of Pd diffraction peaks to lower angles upon the addition of Sn compared to Pd/CNOs. X-ray photoelectron spectroscopy (XPS) results also confirm the doping of Pd with Sn to form a PdSn alloy. Fourier transform infrared spectroscopy (FTIR) displays oxygen, hydroxyl, carboxyl, and carbonyl, which facilitates the dispersion of Pd and Sn nanoparticles. Raman spectrum displays two prominent peaks of carbonaceous materials which correspond to the D and G bands. The Pd-Sn/CNOs electro-catalyst demonstrates improved electro-oxidation of methanol and ethanol performance compared to Pd/CNOs and commercial Pd/C electro-catalysts under alkaline conditions.

Iron Oxide‐Carbon Black Promotional Effect on Palladium Nanoparticles Toward Ethylene Glycol Oxidation in Alkaline Medium: Experimental and Computational Studies

“…The standard curve has a slope of 2.04, which is significant compared to the theoretical value of 0.5 for a diffusion‐controlled reaction of the glassy carbon electrode. [ 42 ] The high slope indicates better electrooxidation kinetics on the Pd/Fe 2 O 3 ‐CB electrocatalyst surface.…”

“…Therefore, the interaction will remarkably influence the electrocatalytic properties of the resulting material due to the synergic effects, thereby promoting their electrooxidation activity, selectivity, stability, and developing poison‐resistant electrocatalysts. [ 6 ] For example, the addition of metal oxides such as NiO, [ 7 ] CeO 2 , [ 8 ] MoO x , [ 9 ] Fe x O x , [ 10 ] and SnO 2 [ 11 ] as promoters to noble metals‐containing composites has been studied as a class of active electrocatalysts. Hydroxyl species (OH − ) easily develop on the surface of the metal mentioned above oxides and aid in oxidizing adsorbed carbonaceous intermediate species during alcohol electrooxidation.…”

Easy preparation of small crystalline Pd2Sn nanoparticles in solution at room temperature

“…As an example, many chemical reactions are selectively catalyzed by metallic NPs 1 and important efforts are thus currently directed toward the preparation of specific NPs which activity can be correlated with their exposed crystalline phases and the number of facets, edges or corners. 2,3 In this context, the development of specific bimetallic alloyed NPs, for example, Pd x Sn y systems has attracted major attention as the addition of metalloid atoms was found to be beneficial for enhancing the catalytic performances when compared to Pd systems for many reactions such as the electro-oxidation of alcohols [4][5][6][7][8] and formic acid, 9 oxidation of dihydrogen into hydrogen peroxide, 10 reduction of nitrates 11,12 and nitro-functional groups 13,14 as well as oxygen, 15,16 or hydrogenation of alkynes, 17,18 dienes, [19][20][21][22] and heterodienes. 23 However, this is not limited to tin and Earth abundant metals could also be used such as Cu 24 or Fe 25 , for instance, to enhance the catalytic performances of catalysts for Heck and Suzuki-Miyaura couplings.…”

“…However, it is extremely difficult to generate well-defined NPs exhibiting controlled size and a unique Pd x Sn y phase. Alternatively, using classical chemical solution protocols, Pd x Sn y bimetallic NPs can also be prepared using surfactants or classical stabilizing agents ( phosphines and/or amines, 4,9 ammonium salts, 10,11 for example) and/or high temperature boiling solvents (oleylamine, 4,6,11 ethylene glycol 7,8 or polyethylene glycol, 21 and ionic liquids 18 ). Interestingly, monodisperse palladiumtin alloyed NPs with tunable compositions and sizes prepared at a high temperature (260 °C) by the co-reduction of tin(II) acetate and palladium(II) bromide in the presence of oleylamine and trioctylphosphine were reported and the specific Pd 63 Sn 37 NPs exhibited promising catalytic activity in Heck 27 and Suzuki-Miyaura 28 reactions, overpassing those of monometallic Pd NPs.…”

Pd3Co1 Alloy Nanocluster on the MWCNT Catalyst for Efficient Formic Acid Electro-Oxidation

“…Doping [ 17 , 26 , 27 , 28 ] is considered to be the most effective method to improve the stability and activity of Pd-alloy catalysts because the doped metal can change the electronic state around the Pd atom, affecting the adsorption of the toxic intermediates and weakening the dissolution of Pd. Tang et al doped Co into Pd to form an alloy, which significantly improved the activity and stability of the catalyst [ 29 ].…”