Oxygen activation on a carbon catalyst support co-doped with Si and transition metals: an electrochemical study

Abstract

Multi-doped carbons are promising thermocatalysts, electrocatalysts, and catalyst supports. Recently, Si-co-doped carbons have emerged as catalyst supports for a range of reductive coupling reactions. However, little is known about their catalytic activity in the oxygen cycle. We now report a detailed electrochemical and material investigation into a range of Si-doped carbons, aimed at correlating their activity towards the reduction of O₂ and H₂O₂ with their composition and structure. We examine a broad range of pyrolysis temperatures (600–1000 °C), combined with several oxygen-active metals (Ag, Mn, Co), co-doped into the Si-, N-doped support either alone or in combinations at different ratios. Using a combination of X-ray diffraction, XPS and Raman spectroscopies, electron microscopy and elemental analysis, we identify the factors contributing to O₂ activation (as expressed in electrochemical O₂ reduction in alkaline) and reactivity towards H₂O₂ production and further reduction. As a result, the precise combination of metal dopants, ratios, and pyrolysis temperatures is identified as optimal for 2e⁻/4e⁻ selectivity in O₂ reduction and total H₂O₂ yield. We hope that these findings will enable better rational design of Si-codoped catalysts supports for many thermocatalytic and electrocatalytic reactions.