Effects of Metal–Oxygen Coordination in Pt–Ru–Sn Electrocatalyst in the Electrochemical Reforming of Aqueous EtOH in a Solid-Polymer-Electrolyte Electrolysis Cell

Abstract

The use of a solid-polymer-electrolyte (SPE) electrolysis cell for the electrochemical reforming of bioethanol to hydrogen is a promising route to utilize biomass to decarbonize hydrogen production through the EtOH electro-oxidation reaction (EOR). We prepared a Ketjenblack (KB)-supported Pt−Ru−Sn catalyst by a NaBH 4 reduction method (Pt−Ru−Sn/KB), which achieved a steady-state current density of 9.4 mA cm −2 at 0.6 V with an EtOH consumption rate of 1.43 mol H2 •mol EtOH −1 . Based on cyclic voltammetry and characterization studies, we found that this activity was due to a three-way synergy between Pt, Ru, and Sn wherein the addition of Sn enhanced the initial oxidative adsorption of EtOH onto Ru and modified the electronic properties of Pt. A lower Sn atomic ratio in the presence of Ru led to higher Pt oxidation, which was directly proportional to EOR activity. Based on the X-ray absorption fine structure (XAFS) studies, both a low metal−metal coordination and a high metal−oxygen coordination resulted in the enhancement of current densities, which suggested that metal atoms surrounded by oxygen atoms were vital to the three-way synergy of the three metals that resulted in enhanced EOR activity; hence, a reaction mechanism was proposed based on these findings.