Boosting methanol electro-oxidation to formate by trace iron induced suppression of cobalt(IV) formation

Converting methanol to high-value formate through electrochemical methods can significantly reduce the energy consumption associated with conventional production processes. In this study, we directly synthesized iron-doped cobalt phosphate (Fe-CoPO) on nickel foam (NF) to achieve excellent activity for the methanol electro-oxidation reaction (MOR). Our results demonstrated that Fe-CoPO produced a current density of 100 mA·cm⁻² at a significantly low operating potential of 1.436 V (vs. reversible hydrogen electrode (RHE)) and operated steadily for 16 h at this current density with a Faradaic efficiency (FE) of 97%. Furthermore, Fe-CoPO maintained a high FE of 100% even at an extremely high current density of 300 mA·cm⁻² for 8 h. We found that the high MOR activity of Fe-CoPO results from electrochemical reconstruction to generate the Co^2+/3+–O bond. The heterogeneous interface between Fe and Co inhibits the formation of Co⁴⁺, which significantly enhances the MOR activity. Thus, this work not only provides insights into the mechanism of MOR over Co-based catalysts but also offers a novel direction for developing highly active MOR catalysts.