Nitrogen-doped rGO-supported 2D MnO₂ catalysts for improved CO₂ electroreduction

Nitrogen-doped reduced graphene oxide (NrGO), manganese dioxide (MnO₂), and a composite (NrGO-MnO) were synthesized via hydrothermal treatment, where the confined hydrothermal conditions facilitate controlled nucleation and anisotropic two-dimensional growth. Structural and morphological analyses confirmed the formation of poorly crystalline MnO fragments uniformly dispersed on the NrGO framework, effectively preventing graphene restacking and enhancing surface accessibility. BET surface area analysis revealed that NrGO-MnO exhibited a significantly higher specific surface area (62.56 m² g^-1) and pore volume (0.39 cm³ g^-1) compared to pristine materials. Electrochemical characterization under CO₂ saturated electrolytes demonstrated that the NrGO-MnO composite outperformed both NrGO and MnO₂. Linear sweep voltammetry revealed a higher current density of approximately 12.0 mA cm^-2 and 16.0 mA cm^-2, respectively at -1.7 V vs. Ag/AgCl for both NrGO and NrGO-MnO electrodes under CO₂ saturated conditions, accompanied by a more positive onset potential around -0.90 to -1.0 V vs. Ag/AgCl In contrast, MnO₂ exhibited a lower current density of about 5.0 mA cm^-2 with a more negative onset potential. Electrochemical impedance spectroscopy revealed lower charge-transfer resistance for NrGO and NrGO-MnO composites compared to MnO₂, indicating enhanced electron and ion transport. The developed NrGO-MnO catalyst demonstrates improved in CH₄ synthesis with a maximum faradaic efficiency of about 27%, emphasising its unique selectivity for deeper CO₂ reduction products. These findings highlight interfacial synergy in catalyst design and offer guidance for developing scalable, high-performance CO₂ electroreduction systems.