Optimizing Metal-free Phenanthroline-assisted Nitrogen-doped Reduced Graphene Oxide for Enhanced Oxygen Reduction Reaction: An Experimental Design and Performance Study

Abstract

Developing efficient and cost-effective oxygen reduction reaction (ORR) catalysts is critical for advancing fuel cell technologies. Based on this, we propose a metal-free reduced graphene oxide (rGO) catalyst produced from graphite as a base material for electrode modification. Nevertheless, by using phenanthroline as a nitrogen precursor, we investigated different synthesis conditions to adjust the electrocatalytic characteristics of the material precisely, aiming for a four-electron mechanism with low onset potential. A comprehensive experimental design revealed that specific preparation parameters (75 mg of phenanthroline, 1079 °C, and 1.73 h) significantly influenced the catalyst’s performance: the optimized catalyst had an increase in current density and a positive shift in the half-wave potential compared to other materials that underwent not optimized synthetic conditions. Morphological and physicochemical characterizations, including SEM and XPS analyses, provided insights into the material’s structure and composition, correlating the observed catalytic performance with graphitic nitrogen and an optimized degree of deoxygenation. Crucially, our study demonstrated a method for achieving varied levels of nitrogen species with the same nitrogen precursor, revealing that, under optimized conditions, the same precursor can yield diverse outcomes. Importantly, the optimized catalyst demonstrated impressive performance, showing only a 0.1 V difference in onset potential compared to the commercial Pt/C catalyst and a limiting current density of 2.1 mA cm⁻². Thus, this study underscores the importance of systematic experimental design and optimization in developing high-performance, metal-free electrocatalysts for energy conversion applications.

Graphical Abstract