Tailoring the catalytically active sites in Co-based catalysts for electrochemical methanol upgrading to produce formate

Abstract

Electrochemical valorization of bulk chemicals to produce value-added fine chemicals is highly attractive and deemed to be a green and economic way to optimize traditional industrial synthesis. The electrochemical methanol upgrading (EMU) process which converts methanol to value-added formate exhibits an expectation of high profit and adherence to the tenets of green chemistry, and it has received substantial interest aimed at discovering highly efficient catalysts with satisfactory operational stability. In this work, focusing on enriching and activating the high-valence cobalt active sites, a hierarchically nanoporous nitrogen-doped carbon-supported Co/CoO hybrid catalyst grown on cobalt foam (Co–N–C/CoO/CF) was fabricated. The high porosity and conductive microchannels could synergistically enrich the local high-valence Co active sites and boost the in situ generation of such sites via an electrochemical pre-oxidation process. Benefitting from the synergy of multiple structural benefits, the Co–N–C/CoO/CF catalyst exhibits robust EMU performance. An ultralow potential of 1.309 V versus a reversible hydrogen electrode can be identified to drive a 50 mA cm⁻² EMU current density, and a high faradaic efficiency (FE) of 98.2% can be achieved. In addition, with the merits of high structural stability, excellent operational stability can be achieved for Co–N–C/CoO/CF with negligible degradation in either current density or FE for at least 120 h, making the catalyst the most stable catalyst to date for methanol-to-formate upgrading. Its high activity and excellent operational stability make the Co–N–C/CoO/CF catalyst a promising candidate for green and economic formate electrosynthesis via partial methanol electro-oxidation.