Controlled synthesis of MOF-derived hollow and yolk–shell nanocages for improved water oxidation and selective ethylene glycol reformation

Delicately designed metal–organic framework (MOF)-derived nanostructured electrocatalysts are essential for improving the reaction kinetics of the oxygen evolution reaction and tuning the selectivity of small organic molecule oxidation reactions. Herein, novel oxalate-modified hollow CoFe-based layered double hydroxide nanocages (h-CoFe-LDH NCs) and yolk–shell [email protected] nanocages ([email protected] NCs) are developed through an etching–doping reconstruction strategy from a Co-based MOF precursor (ZIF-67). The distinctive nanostructures, along with the incorporation of the secondary metal element and intercalated oxalate groups, enable h-CoFe-LDH NCs and [email protected] NCs to expose more active sites with high intrinsic activity. The resultant h-CoFe-LDH NCs exhibit outstanding OER activity with an overpotential of only 278 mV to deliver a current density of 50 mA cm−2. Additionally, controlling the reconstruction degree enables the formation of [email protected] NCs with a yolk–shell nanocage nanostructure, which show outstanding electrocatalytic performance for the selective ethylene glycol oxidation reaction (EGOR) toward formate, with a Faradaic efficiency of up to 91%. Consequently, a hybrid water electrolysis system integrating the EGOR and the hydrogen evolution reaction using Pt/C||[email protected] NCs is explored for energy-saving hydrogen production, requiring a cell voltage 127 mV lower than water electrolysis to achieve a current density of 50 mA cm−2. This work demonstrates a feasible way to design advanced MOF-derived electrocatalysts toward enhanced electrocatalytic reactions.