PNNL

Abstract

Electrochemical hydrogenation (ECH) is a promising method for upgrading biomass derived oxygenates into bio-fuels at near ambient conditions without the need for external hydrogen (H2). Although the ECH approach has many advantages over conventional thermochemical methods, the selective production of fully deoxygenated hydrocarbons remains a key challenge. In this study we explore the ECH of phenol as a bio-oil-derived model compound using carbon supported metal electrocatalysts in a custom-made divided electrochemical batch cell. We demonstrated ECH of phenol to cyclohexane and investigated the effect of multiple variables, including catalyst type, electrolyte composition and concentration, and cathodic potential to determine their influence on ECH reaction rate, selectivity, and Faradaic efficiency (FE). The results obtained show that lab-synthesized, bi-metallic PtRu-C catalyst results in the highest specific ECH rate of 23.52 mol h-1 g-1metal in comparison to 15.84 mol h-1 g-1metal and 4.64 mol h-1 g-1metal, measured with mono-metallic Pt-C and Ru-C catalysts, respectively. In addition, the PtRu-C electrocatalyst achieved > 30% selectivity towards cyclohexane while monometallic the Pt and Ru only achieved 25 and 11%, respectively. Operando Raman spectroscopy found strong evidence for cyclohexanone reaction intermediates.