Influence of Pd‐Au/MWCNTs surface treatment on catalytic activity in the formic acid electrooxidation

Abstract

Influence of different treatments of Pd‐Au/MWCNTs prepared by a modified polyol microwave‐assisted method on the morphology and the catalytic activity in the formic acid electrooxidation was investigated. The following standard treatments were applied to purify the metal particles surface from the carbonaceous deposits formed from ethyl glycol adsorbed on the catalyst after the preparation: 1. annealing in air at 300 °C, 2. annealing in air at 300 °C and then reduction in 5%H2/Ar at 200 °C, 3. reduction in 5%H2/Ar at 200 °C. Surprisingly, the most catalytically active sample was that without additional purification treatments. The TEM, XRD and electron spectroscopy methods were applied to characterise the catalysts. Two Pdx Au1–x phases are present in all catalysts. The treatment number 1 and 2 caused: 1. partial removing of the carbonaceous deposits from the metal surface, 2. increases metal particle sizes, 3. decreases of Pd rich phase content, 4. increases ratio of Au to Pd in the catalyst surface layer. Treatment number 4 did not change significantly the sample morphology but decreased its catalytic activity in formic acid fuel cell. It can be due oligomerization of carbon deposits during thermal treatment in reducing (H2) atmosphere (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

One-pot synthesis of gold–palladium@palladium core–shell nanoflowers as efficient electrocatalyst for ethanol electrooxidation

“…Recently, various palladium-based bimetallic nanostructures (such as palladium-copper, palladium-platinum, and palladium-gold) with well-defined morphologies, excellent catalytic activities, and stabilities have been widely reported [4][5][6][7][8]. Among them, palladium-gold (Pd-Au) bimetallic nanocrystals, especially gold@palladium (Au@Pd) core-shell nanostructures have been widely used as effective catalysts for methanol oxidation reaction [9][10][11], oxygen reduction reaction [12,13], formic acid oxidation reaction [14], and ethanol oxidation reaction (EOR) [15][16][17][18], etc. For example, Lu and co-workers demonstrated that Au@Pd core-shell nanocrystals with octahedral shape exhibited the electrocatalytic activity increased by 2 times than these nanocrystals with other shapes for the EOR [19].…”

Carbon‐supported AuPt and AuPd bimetallic nanocomposites as formic acid electrooxidation catalysts

“…Comparing electrocatalytic activity of nanocomposite AuPd/VC‐5 with other reported carbon‐supported AuPd alloy nanocomposites is complicated by differences in metal alloy composition, nanocomposite physical properties, testing conditions, and electrochemical test method. AuPd(35:65)/multi‐walled carbon nanotube (MWCNT) nanocomposites prepared by polyol reduction of PdCl 2 and HAuCl 4 · 3H 2 O perform well as electrooxidation catalyst in formic acid/oxygen fuel cells giving maximum power density of 64 mW mg −1 AuPd at a current density of 135 mA mg −1 AuPd catalyst . Similarly prepared AuPd/MWCNT nanocomposites subjected to a post‐synthesis H 2 thermal reduction treatment give oxidation currents near 800 mA mg −1 total metal when tested on a rotating disk electrode in 3 M HCOOH/1 M H 2 SO 4 .…”

Influence of the preparation conditions ofPd‐ZrO2andAuPd‐ZrO2nanoparticle–decorated functionalisedMWCNTs: Electron spectroscopy study aided with theQUASES

“…Among these, metal‐ and/or metal oxide‐decorated CNTs devoted a high interest because of their technological application in catalysis, bio/chemical sensoring, energy storage and production, individual electrical CNT properties studies, etc. For a catalytic purpose, the metal (mainly Pd substituting Pt) and AuPd catalysts supported multiwalled carbon nanotubes (MWCNTs), and recently, Pd‐ZrO 2 and AuPd‐ZrO 2 on functionalised MWCNTs (f‐MWCNTs) were applied. These Pd‐ and AuPd‐decorated f‐MWCNTs catalysts of formic acid (FA) electro‐oxidation (on an anode side), prepared with the same metal loading (20 wt%) using different methods, provided information on their higher catalytic activity exceeding the respective for Pt catalysts.…”

“…For a catalytic purpose, the metal (mainly Pd substituting Pt) and AuPd catalysts supported multiwalled carbon nanotubes (MWCNTs), and recently, Pd‐ZrO 2 and AuPd‐ZrO 2 on functionalised MWCNTs (f‐MWCNTs) were applied. These Pd‐ and AuPd‐decorated f‐MWCNTs catalysts of formic acid (FA) electro‐oxidation (on an anode side), prepared with the same metal loading (20 wt%) using different methods, provided information on their higher catalytic activity exceeding the respective for Pt catalysts. The modified 20 wt% Pd‐ZrO 2 /f‐MWCNTs and 10 wt% Au 10 wt% Pd‐ZrO 2 /f‐MWCNTs catalysts showed smaller catalytic activity than the same catalysts without ZrO 2 because of larger nanoparticle size, however, were shown to be more resistant for deactivation and sintering of nanoparticles because of thermochemical treatment in oxygen and hydrogen.…”