Interfacial Pd–O–Ce Linkage Enhancement Boosting Formic Acid Electrooxidation

Abstract

Metal−support interaction enhancement is critical in the fuel cell catalyst design and fabrication. Herein, taking the Pd@CeO 2 system as an example, we revealed the substrate morphology coupling effect and the thermal annealinginduced Pd−O−Ce linkage enhancement in the improved catalytic capability for formic acid electrooxidation. Three well-defined CeO 2 nanocrystals were employed to support Pd nanoparticles, and the best catalytic performance for formic acid oxidation and anti-CO poisoning ability was found on CeO 2 plates because of the high oxygen vacancy, Ce 3+ , and more Pd−O−Ce linkages resulting from the more edge/corner defects. This interaction of Pd−O−Ce linkages could be largely enhanced by thermal annealing in the N 2 atmosphere, as confirmed by a series of crystal structures, surface chemical state, and Raman analysis because the oxygen vacancies and lattice oxygen resulting from the oxygen atoms leaching from the CeO 2 lattice would trap the mobile Pd nanocrystals by forming strengthened Pd−O−Ce linkages. Due to the high oxygen vacancy and strong Pd−O−Ce linkages, largely increased catalytic activity and stability, catalytic kinetics, and rapid charge transfer were found for all the thermal annealed Pd@CeO 2 catalysts. A nearly 1.93-fold enhancement in the mass activity was achieved on the Pd@CeO 2 -plate catalysts demonstrating the significance of Pd−O−Ce linkage enhancement. The formation mechanism of Pd−O−Ce linkage was also probed, and a valid Pd−O−Ce linkage can only be formed in the inert atmosphere because of the reaction between metallic Pd and CeO 2 . This finding sheds some light on the more efficient catalyst interface construction and understanding for the fuel cell catalysis via metal−support interaction enhancement.

Pt1(CeO2)0.5 Nanoparticles Supported on Multiwalled Carbon Nanotubes for Methanol Electro-oxidation

“…The average size of Pt calculated from HRTEM images is 4.3 nm (Figure C), which is quite near to the abovementioned result obtained from the XRD data and smaller than that of Pt 1 (CeO 2 ) 0.5 /MWCNTs-W (Figure S2, 6.1 nm) and the reported values. , Besides, the particle size of CeO 2 computed from the CeO 2 (311) diffraction peak using the Scherrer’s equation is 3.0 nm. Compared with the other literature studies, ,, the particle size of CeO 2 of Pt 1 (CeO 2 ) 0.5 /MWCNTs-D is much smaller, which demonstrates that DESs are beneficial to reduce the particle size of CeO 2 . Meanwhile, the three peaks of Pt, Ce, and O are presented in EDX spectra (Figure D).…”

“…44,45 Besides, the particle size of CeO 2 computed from the CeO 2 (311) diffraction peak using the Scherrer's equation 46 is 3.0 nm. Compared with the other literature studies, 43,46,47 the particle size of CeO 2 of Pt 1 (CeO 2 ) 0.5 /MWCNTs-D is much smaller, which demonstrates that DESs are beneficial to reduce the particle size of CeO 2 . Meanwhile, the three peaks of Pt, Ce, and O are presented in EDX spectra (Figure 2D).…”

PdNi/N-doped graphene aerogel with over wide potential activity for formic acid electrooxidation

“…Thus, GAs are advantageous over pristine graphene, having the 2D structure, in terms of efficient ion and molecule transport and diffusion and large surface area [18,19]; thus, they might be a suitable support for advanced Pd-based catalysts. Moreover, oxophilicity is desirable in Pd-based catalysts because the easy generation of oxygen-containing species prevents the accumulation of poisoning intermediates [20,21]. The Pd-Ni alloy is an active phase for formic acid oxidation because of its anti-poisoning ability, which is improved by the oxophilicity of Ni [22,23].…”

Porous palladium phosphide nanotubes for formic acid electrooxidation

“…[13][14][15] In general, FAEOR occurs through two reaction mechanisms (i.e., direct and indirect pathways). 16,17 The former directly oxidizes FA to carbon dioxide (CO 2 ) through the dehydrogenation pathway, while the latter is to form toxic carbon monoxide intermediate (CO ads ) through the dehydration pathway and then oxidize to generate CO 2 . The indirect pathway with strong poisonous intermediates greatly reduces the efficiency of DFAFC.…”