Evaluation of supported and unsupported Pd–CeO2 nanostructured anode electrocatalysts for the formic acid and the glycerol oxidation reactions in acid media

Abstract

The catalytic activity of Pd-CeO 2 /C and nonsupported Pd-CeO 2 electrocatalysts for the formic acid (FAOR) and glycerol oxidation reaction (GOR) is evaluated in this work. The materials have been synthesized by pyrolysis in H 2 atmosphere at 300 and 600°C, with a nominal Pd:CeO 2 ratio of 1:1. X-ray diffraction analysis demonstrates polycrystalline materials with particles sizes ranging from 11 to 14 nm (Pd) and 26 to 48 nm (CeO 2 ). Electrocatalytic measurements show a positive effect of dispersing the catalysts on Vulcan in the case of the FAOR, in terms of potential-current density profile and onset potential. While unsupported Pd-CeO 2 nanoparticles behave poorly, the Pd-CeO 2 /C anodes show a very high performance towards the FAOR. Particularly, Pd-CeO 2 /C obtained at 600°C shows a significantly high catalytic activity, with a higher mass current density than a comparable Pd/C electrocatalyst. X-ray photoelectron spectroscopy analysis undoubtedly demonstrates that the carbon support has an important effect on the oxidation states of Pd and CeO 2 , which in turns influences positively the catalytic behavior of Pd-CeO 2 /C catalysts. Furthermore, both supported and unsupported Pt-CeO 2 materials have shown no catalytic activity for the GOR. The results indicate that Pd-CeO 2 /C electrocatalysts can be considered as excellent candidate anodes for direct formic acid fuel cells.

Electrocatalyst Performances in Direct Alcohol Fuel Cells: Defect Engineering Protocols, Electrocatalytic Pathways, Key Parameters for Improvement, and Breakthroughs on the Horizon

“…[173,226] For the successful electrochemical conversion of the higher alcohols, alkaline conditions are much more favored. [15,227] However, the need for high alkaline conditions inhibits polyhydric-based FCs' use in normal operational conditions, hence limiting their entire application. The main reason for that is the inherent poisoning of the electrolyte by carbon dioxide, be it from the air or the oxidation process.…”

“…These strategies typically alter the active sites' chemical environment modulation of the electronic structure, which inherently amplifies the charge transfer and electron mobilities. [4,5] Metallic-based (platinum group metals [PGMs], e.g., Pd, Pt, Ru, [6][7][8] and non-PGMs, e.g., carbon-based, [9][10][11] metal oxides, [12][13][14][15][16] nitrides) [17][18][19] have been investigated. However, because of the absence of highly sophisticated characterization techniques in the past, electrocatalytic contribution effects of defects and doping on electrocatalysts' performance have not been fully elucidated.…”

Recent advances in electrocatalysts, mechanism, and cell architecture for direct formic acid fuel cells

“…The MPD obtained for a single cell was 2.85 and 2.65 times higher than Pt/C and Pd black, respectively (M. Choi et al, 2019). Doping noble metals with metal oxides like Fe 3 O 4 and CeO 2 is beneficial because they are found to act as oxygen buffers to provide OH species at relatively low overpotentials and promote oxidation of adsorbed CO to CO 2 (Altamirano‐Gutiérrez et al, 2015; Habibi & Delnavaz, 2015; Meléndez‐González et al, 2017).…”

Bifunctional Pd‐CeO2 Nanorods/C Nanocatalyst with High Electrochemical Stability and Catalytic Activity for the ORR and EOR in Alkaline Media

“…It is well known that CeO 2 acts as an oxygen buffer, forming OH À species at more negative potentials than some noble metals. [56] The OH À species transferred onto neighboring Pd sites participate in the removal of carbonaceous species, making them available to carry out the oxidation reaction, i. e., the bifunctional mechanism. [57] There is also the possibility of redeposition of dissolved Pd from the solution to the nanocatalyst.…”