Electrocatalytic water oxidation on CuO-Cu2O modulated cobalt-manganese layered double hydroxide.

Layered double hydroxides (LDH) are potential electrocatalysts to address the sluggish oxygen evolution reaction (OER) of water splitting. In this work, copper oxide (CuO/Cu2O) nanoparticles are integrated with cobalt-manganese layered double hydroxide (CoMn-LDH) to enhance their performance towards OER. The catalyst is synthesized by growing CoMn-LDH nanosheets in the presence of CuO/Cu2O nanoparticles that were obtained by the calcination of the copper containing metal-organic framework (HKUST-1). The synthesized CoMn-LDH@CuO/Cu2O electrocatalyst shows excellent activity towards OER with an overpotential of 297 mV at a catalytic current density of 10 mA cm-2 and have a Tafel slope value of 89 mV dec-1. Moreover, a slight decrease in the performance parameters is observed until the 15 h of continuous operation. We propose that the conductive strength of CuO/Cu2O and its synergistic effect with the CoMn-LDH are responsible for the improved OER performance of the desired electrocatalyst.

ZIF-12/Fe-Cu LDH Composite as a High Performance Electrocatalyst for Water Oxidation.

Layered double hydroxides (LDH) are being used as electrocatalysts for oxygen evolution reactions (OERs). However, low current densities limit their practical applications. Herein, we report a facile and economic synthesis of an iron-copper based LDH integrated with a cobalt-based metal-organic framework (ZIF-12) to form LDH-ZIF-12 composite (1) through a co-precipitation method. The as-synthesized composite 1 requires a low overpotential of 337 mV to achieve a catalytic current density of 10 mA cm-2 with a Tafel slope of 89 mV dec-1. Tafel analysis further demonstrates that 1 exhibits a slope of 89 mV dec-1 which is much lower than the slope of 284 mV dec-1 for LDH and 172 mV dec-1 for ZIF-12. The slope value of 1 is also lower than previously reported electrocatalysts, including Ni-Co LDH (113 mV dec-1) and Zn-Co LDH nanosheets (101 mV dec-1), under similar conditions. Controlled potential electrolysis and stability test experiments show the potential application of 1 as a heterogeneous electrocatalyst for water oxidation.