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 ZIF@CoFe-LDH nanocages (ys-ZIF@CoFe-LDH 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 ys-ZIF@CoFe-LDH 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 ys-ZIF@CoFe-LDH NCs with a yolk-shell nanocage nanostructure, which show outstanding electrocatalytic perfor-mance 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||ys-ZIF@CoFe-LDH 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.

Automated summary

In this work, novel nanostructured electrocatalysts are developed through an etching-doping reconstruction strategy from a Co-based MOF precursor. These electrocatalysts exhibit outstanding performance in the oxygen evolution reaction and the oxidation of small organic molecules.