Trimetallic-organic framework/MXene composite as an oxygen evolution reaction electrocatalyst with elevated intrinsic activity

Abstract

The development of high-efficiency non-noble metal electrocatalysts for the oxygen evolution reaction (OER) is a paramount challenge in the area of energy. Metal–organic frameworks with open metal sites and mixed transition-metal clusters in combination with excellent metal-conductive MXene nanosheets as a two-dimensional support would result in superconductive and stable composites with abundant accessible reactive sites, which are known to be highly effective OER electrocatalysts with great intrinsic activity. Here, a composite of trimetallic Fe_2.1Ni_0.2Co_0.7-MIL-88A grown on Ti₃C₂T_x MXene nanosheets was successfully synthesized and fully characterized by TEM, FESEM, EDX, XRD, XPS, FT-IR and electrochemical techniques. Both the MOF and the MOF/MXene composite effectively catalyze the OER in alkaline media, providing a current density of 10 mA cm⁻² at overpotentials of 231 and 260 mV and a very low Tafel slope of 34.5 and 42.9 mV dec⁻¹ by the MOF/MXene and MOF, respectively. The MOF/MXene composite exhibits a fascinating TOF of 2.33 s⁻¹ at η_{270 mV} and long-term stability for 24 h without recognizable changes in overpotential. This study proposes that the multi-metallic active sites generated by the trimetallic MOFs as well as the higher exposure of catalytic active sites due to the presence of hydrophilic, conductive Ti₃C₂T_x nanosheets, create a desirable and robust OER electrocatalyst with considerable synergistic and electronic effects.