Self-recoverable Pd–Ru/TiO2 nanocatalysts with ultrastability towards ethanol electrooxidation

Abstract

Self-recoverable Pd–Ru/TiO₂ nanocatalysts have been prepared by electrochemical stripping of Pd–Ru/TiO₂ precursors. For the ethanol oxidation reaction (EOR), these Pd–Ru/TiO₂ nanocatalysts are used as an anode catalyst. The characterization of catalysts via chronoamperometry has been repeated 15 times. After 15 stability tests, the Pd₁Ru_0.69/TiO₂ nanocatalysts still achieve a factor of 9.4 enhancement at the residual current density (309.42 mA mg_Pd⁻¹) for the EOR over commercial Pd/C catalysts (33.01 mA mg_Pd⁻¹). From the 5^th to 15^th test, when each 10 000 s stability test is performed in a fresh ethanol electrolyte, the initial and residual current density of the catalysts could recover to the original or even better value in a few hours before performing another 10 000 s stability test. Herein, these Pd–Ru/TiO₂ nanocatalysts with ultrastability towards ethanol electrooxidation are self-recoverable. Density functional theory calculations reveal that the introduction of oxophilic metal Ru and a TiO₂ support into Pd-based catalysts and the synergistic effects between Ru and TiO₂ have led to the ultrastability towards the EOR. The introduction of oxophilic metal Ru and a TiO₂ support into catalysts can reduce the adsorption energy of OH_ads on the Pd–Ru/TiO₂ nanocatalysts, and it will inhibit the CO_ads produced and adsorbed on the Pd surface.