Efficient Oxidation of Ethanol at Ru@Pt Core-Shell Catalysts in a Proton Exchange Membrane Electrolysis Cell

Abstract

Efficient electrochemical oxidation of ethanol in fuel cells and electrolysis cells is important for generating power and hydrogen, respectively, from renewable resources. PtRu alloys are most widely employed as catalysts because they provide high activities at low potentials. However, they produce acetic acid as the main product from ethanol, which results in low faradaic and overall efficiencies. In contrast, Pt provides high selectivity for the complete oxidation of ethanol to CO2, but low activities. Ru@Pt core-shell nanoparticles can improve efficiency by delivering higher activity than Pt and enhanced formation of CO2 relative to PtRu. Here, Ru@Pt catalysts have been prepared by depositing Pt onto a commercial carbon-supported Ru catalyst. The influence of the amount of Pt deposited has been investigated in H2SO4(aq) at ambient temperature and in a proton exchange membrane cell at 80°C. Activities for ethanol oxidation were intermediate between those for commercial Pt and PtRu catalysts, providing higher currents than Pt at low potentials, and higher currents than PtRu at high potentials. Faradaic yields of CO2 (38-48%) were greatly increased relative to the PtRu alloy catalyst (11%). This will optimize the efficiency of ethanol oxidation in proton exchange membrane electrolysis and fuel cells.

Cryogels from Pt/γ-Fe2O3 and Pd/γ-Fe2O3 NPs as Promising Electrocatalysts for Ethanol Oxidation Reaction

“…This overpotential can be attributed to the low oxophilicity of Pt and Pd which hinders the first chemisorption step of ethanol on the catalyst surface. So, lowering the overpotentials is a crucial step to obtain efficient electrocatalysis of EOR [30].…”

Electrochemical Oxidation of Ethanol and Methanol at Rh@Pt Catalysts at 80 °C in Proton Exchange Membrane (PEM) Cells

“…S5A shows a comparison of polarization curves for the Rh@Pt(0.5 ML) and Rh@Pt(2.0 ML) catalysts in the 9-anode PEM cell with data for a commercial PtRu alloy catalyst and the most active Ru@Pt core-shell catalyst (with 2.0 ML of Pt) from a previous report. 29 This makes it clear that Rh@Pt catalysts are not competitive with Ru based catalysts for methanol electrolysis. Unlike ethanol, partial oxidation of methanol is not a significant issue, and so use of Rh is unnecessary.…”

“…Typically, one to three monolayer Pt shells are deposited onto a more electropositive core in order to minimize Pt consumption and improve catalytic activity and stability. [17][18][19][20][21][22][23][24][25][26][27][28][29] The core metal can increase the catalytic activity of the Pt surface while retaining Pt-like selectivity. [27][28][29] The strain effect and electronic interaction between the core and shell atoms significantly influence catalytic performance.…”

“…[17][18][19][20][21][22][23][24][25][26][27][28][29] The core metal can increase the catalytic activity of the Pt surface while retaining Pt-like selectivity. [27][28][29] The strain effect and electronic interaction between the core and shell atoms significantly influence catalytic performance. 17,25,[30][31][32] Many studies have concentrated on Pt-Ru and Pt-Sn bimetallic electrocatalysts because these combinations show much lower onset potentials than Pt for ethanol oxidation.…”

“…11,14,33 However, the major products are acetic acid and acetaldehyde due to disruption of the surface Pt ensembles (2-3 adjacent Pt atoms) required for breaking the C-C bond. 34 Recent studies have shown that the deleterious effect of Ru on the selectivity of Pt for CO 2 formation can be mitigated by employing Ru@Pt 27,29 or PtRu@Pt 28 nanoparticles with core-shell structures. These combine the beneficial effect of Ru in the core with the selectivity of a pure Pt surface for C-C bond cleavage.…”