Electrocatalytic Hydrogenation of Phenol over Platinum and Rhodium: Unexpected Temperature Effects Resolved

Abstract

Both electrocatalytic hydrogenation (ECH) and thermal catalytic hydrogenation (TCH) of phenol by Pt and Rh show a roll-over in rate with increasing temperature without changing the principal reaction pathways. The negative effect of tempera-ture for aqueous-phase phenol TCH and ECH on Pt and Rh is deduced to be from dehydrogenated phenol adsorbates, which block active sites. ECH and TCH rates increase similarly with increasing hydrogen chemical potential whether in-duced by applied potential or H2 pressure, both via increasing H coverage, and indirectly by removing site blockers, a strong effect at high temperature. This enables unprecedented phenol TCH rates at 60-100 °C.