Thermally reduced mesoporous manganese MOF @reduced graphene oxide nanocomposite as bifunctional electrocatalyst for oxygen reduction and evolution

Abstract

Oxygen electrocatalysis plays a crucial role in harnessing energy from modern renewable energy technologies like fuel cells and metal–air batteries. But high cost and stability issues of noble metal catalysts call for research on tailoring novel metal–organic framework (MOF) based architectures which can bifunctionally catalyze O₂ reduction and evolution reactions (ORR & OER). In this work, we report a novel manganese MOF @rGO nanocomposite synthesized using a facile self-templated solvothermal method. The nanocomposite is superior to commercial Pt/C catalyst both in material resource and effectiveness in application. A more positive cathodic peak (E_pc = 0.78 V vs. RHE), onset (E_onset = 1.09 V vs. RHE) and half wave potentials (E_1/2 = 0.98 V vs. RHE) for the ORR and notable potential to achieve the threshold current density (E_{@10 mA cm⁻²}= 1.84 V vs. RHE) for OER are features promising to reduce overpotentials during ORR and OER. Small Tafel slopes, methanol tolerance and acceptable short term stability augment the electrocatalytic properties of the as-prepared nanocomposite. Remarkable electrocatalytic features are attributed to the synergistic effect from the mesoporous 3D framework and transition metal–organic composition. Template directed growth, tunable porosities, novel architecture and excellent electrocatalytic performance of the manganese MOF @rGO nanocomposite make it an excellent candidate for energy applications.