MOF-templated CuO and Mn[sbnd]CuO/Cu2O composites as electrocatalyst in oxygen evolution

Abstract

Considering the great need for the development of new electrocatalysts for oxygen evolution reaction (OER), this work reports the synthesis and characterization of four new copper-based electrocatalysts derived from metal–organic frameworks (MOFs). Homometallic (CuIDA, [Cu(IDA)(H2O)2]n IDA= iminodiacetate) and heterobimetallic [Cu0.902Mn0.096(IDA)(H2O)2]n, [Cu0.703Mn0.297(IDA)(H2O)2]n and [Cu0.487Mn0.513(IDA)(H2O)2]n MOFs were obtained by precipitation method and characterized by X-ray diffraction (XRD) with Rietveld refinement, infrared spectroscopy (FT-IR) and thermogravimetric (TGA). The calcination of CuIDA and heterobimetallic MOFs under air atmosphere led to the formation of CuO and CuO/Cu2O/Mn-x (x = 10 %, 20 % and 50 % of Mn) electrocatalyst, respectively. These materials were characterized by XRD, FT-IR, Raman spectroscopy, UV–vis spectroscopy and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), confirming the chemical composition and crystal structure. Copper oxide-based materials were applied as electrocatalyst for OER in alkaline medium, with overpotential of 359 mV (CuO), 355 mV (CuO/Cu2O/Mn10), 360 mV (CuO/Cu2O/Mn30) and 355 mV (CuO/Cu2O/Mn50) to record a current density of J = 10 mA cm−2. Tafel slope values indicate the adsorption of intermediate species as the rate-determining step for all electrocatalysts. These results are similar or superior to those found in the literature so far.