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.