The Role of Electrodeposited Pd Catalyst Loading on the Mechanisms of Formic Acid Electro-Oxidation

Mechanistic effects of blending formic acid with ethanol on Pd activity towards formic acid oxidation in acidic media

The direct formic acid fuel cell (DFAFC) is one of the most promising direct liquid fuel cells. Pd is the most active catalyst towards formic oxidation, however, it suffers from CO-like poisoning and instability in acidic media. Blending formic acid with ethanol is known to synergistically enhance the Pt catalytic activity of Pt. However, it has not been studied in the case of Pd. In this study, ethanol/formic acid blends were tested, aiming at understanding the effect of ethanol on the formic acid oxidation mechanism at Pd and how the direct and indirect pathways could be affected. The blends consisted of different formic acid (up to 4 M) and ethanol (up to 0.5 M) concentrations. The catalytic activity of a 40% Pd/C catalyst was tested in 0.1 M H₂SO₄ + XFA + YEtOH using cyclic voltammetry, while the catalyst resistance to poisoning in the presence and absence of ethanol was tested using chronopotentiometry. The use of these blends is found to not only eliminate the indirect pathway but also slowly decrease the direct pathway activity too. That is believed to be due to the different ethanol adsorption orientations at different potentials. This study should open the door for further studying the oxidation of FA/ethanol blends using different pHs and different Pd-based catalysts.

Ethanol changes the Pd selectivity towards the different pathways of formic acid oxidation by eliminating the indirect pathway and slowly decreasing the direct pathway activity, owing to ethanol potential depdant adsorption orientations.

Salt-Templated Platinum-Copper Porous Macrobeams for Ethanol Oxidation

Platinum nanomaterials provide an excellent catalytic activity for diverse applications and given its high cost, platinum alloys and bi-metallic nanomaterials with transition metals are appealing for low cost and catalytic specificity. Here the synthesis of hierarchically porous Pt–Cu macrobeams and macrotubes templated from Magnus’s salt derivative needles is demonstrated. The metal composition was controlled through the combination of [PtCl4]2− with [Pt(NH3)4]2+ and [Cu(NH3)4]2+ ions in different ratios to form salt needle templates. Polycrystalline Pt–Cu porous macrotubes and macrobeams 10’ s–100’ s μm long with square cross-sections were formed through chemical reduction with dimethylamine borane (DMAB) and NaBH4, respectively. Specific capacitance as high as 20.7 F/g was demonstrated with cyclic voltammetry. For macrotubes and macrobeams synthesized from Pt2−:Pt2+:Cu2+ salt ratios of 1:1:0, 2:1:1, 3:1:2, and 1:0:1, DMAB reduced 3:1:2 macrotubes demonstrated the highest ethanol oxidation peak currents of 12.0 A/g at 0.5 mV/s and is attributed to the combination of a highly porous structure and platinum enriched surface. Salt templates with electrochemical reduction are suggested as a rapid, scalable, and tunable platform to achieve a wide range of 3-dimensional porous metal, alloy, and multi-metallic nanomaterials for catalysis, sensor, and energy storage applications.

Formate: A Possible Replacement for Formic Acid in Fuel Cells

We present a facile thermodynamic strategy for identifying formate electrooxidation at a Pt electrode in a fuel cell. Mixtures of formate and sulfuric acid are used as fuel solutions for maintaining formic acid at a low concentration and reducing CO poisoning of the Pt electrode. Pt is modified by a polyaniline porous film to improve the electrocatalytic activity towards formate oxidation. The result indicates that formate can bypass the poisoning path to form CO2 at a low potential. Additionally, we propose a new mechanism of formate electrooxidation and investigate the possibility of an independent oxidation path starting from free formate in solution.

Galvanic replacement of electrodeposited nickel by palladium and investigation of the electrocatalytic activity of synthesized Pd/(Ni) for hydrogen evolution and formic acid oxidation

Highly active Pd/(Ni) catalysts were synthesized by well controlled galvanic replacement of electrodeposited nickel, towards hydrogen evolution and FA oxidation.