Toward Overcoming the Challenges in the Comparison of Different Pd Nanocatalysts: Case Study of the Ethanol Oxidation Reaction

Abstract

Precious metal nanoparticles, in particular palladium nanomaterials, show excellent catalytic properties and are key in the development of energy systems. For instance, ethanol fuel cells are promising devices for sustainable energy conversion, where Pd-based catalysts are key catalysts for the related ethanol oxidation reaction (EOR). Pd is a limited resource; thus, a remaining challenge is the development of efficient and stable Pd-based catalysts. This calls for a deeper understanding of the Pd properties at the nanoscale. This knowledge can be gained in comparative studies of different Pd nanomaterials. However, such studies remain challenging to perform and interpret due to the lack of cross-studies using the same Pd nanomaterials as a reference. Here, as-prepared sub 3 nm diameter surfactant-free Pd nanoparticles supported on carbon are obtained by a simple approach. The as-prepared catalysts with Pd loading 10 and 30 wt % show higher activity and stability compared to commercially available counterparts for the EOR. Upon electrochemical testing, a significant size increase and loss of electrochemical active surface are observed for the as-prepared catalysts, whereas the commercial samples show an increase in the electrochemically active surface area and moderate size increase. This study shines light on the challenging comparison of different catalysts across the literature. Further advancement in Pd (electro)catalyst design will gain from including self-prepared catalysts. The simple synthesis detailed easily leads to suitable nanoparticles to be used as a reference for more systematic comparative studies of Pd catalysts across the literature.

Surfactant-Free Colloidal Syntheses of Gold-Based Nanomaterials in Alkaline Water and Mono-alcohol Mixtures

“…Comparing NPs obtained by different methods remains a general challenge because the NPs are often characterized by different protocols using, for instance, different electrolyte concentrations, different EtOH concentrations for the EOR, different upper and lower limit potentials, different scan rates, different numbers of scans, different pretreatments in general, and different ink formulations in the case of supported electrocatalysts, not to mention that different normalizations are used to report the results, etc. 27,49,87 Nevertheless, the activity achieved here is relatively high for Au x Pd y catalysts 88,89 or comparable to that reported elsewhere but using more complex synthetic approaches. 85 In this respect, the readily active NPs obtained here by a simple method can be envisioned as a promising reference material for future studies across different laboratories for improved comparative studies.…”

Surfactant-Free Colloidal Syntheses of Precious Metal Nanoparticles for Improved Catalysts

“…We also showed that the solvent from the synthesis can be recycled several times. In our latest development, the synthesis could be performed at room temperature, ,, and a strong influence of the reducing properties of the solvent was shown . Pt has been the most studied material, and size controlled was achieved using alcohol/water mixtures.…”

Ultrafine PdAgAu alloy nanowires for ethanol oxidation electrocatalysis

“…[10][11][12] At present, Pd-based nanomaterials are considered as one of the most effective EOR catalysts with excellent catalytic activity. [13][14][15][16][17][18][19] Nevertheless, the carbonaceous intermediates produced during the EOR will be adsorbed on the surface of Pd-based catalysts, which will reduce the catalytic performance. [20][21][22][23] Therefore, the development of durable Pd-based catalysts with high activity and efficiency is very important for the EOR.…”