Coking-driven activation of NixFe3-xO4 doped waste-derived carbon: From methanol decomposition to enhanced alkaline OER catalysis

Abstract

Hydrogen production via methanol decomposition is a promising route for sustainable energy, but catalyst deactivation due to coking remains a major challenge. The issue is even more critical for low-cost catalysts, as their reuse or disposal poses environmental and economic concerns. In this study, activated carbon derived from industrial coal-tar pitch waste was modified through two different hydrazine-based thermal treatments, doped with 40 wt% Ni_xFe_3-xO₄ spinels, and subjected to prolonged methanol decomposition to induce coking. All synthesized and spent catalysts were tested for the alkaline oxygen evolution reaction (OER). Notably, the coked catalyst derived from low-temperature hydrazine treatment exhibited improved electrocatalytic performance compared to the parent materials, achieving considerably lower OER overpotentials due to an increased electrochemically active surface area and reduced charge transfer resistance. The carbon coking induced by the methanol decomposition was found to be beneficial for enhancing the overall electrochemical properties of the catalyst depending on their preparation procedure. These findings highlight a new strategy for repurposing spent catalysts in electrocatalytic applications, offering a sustainable approach to catalyst lifecycle management.