Layer-by-layer assembly of exfoliated layered double hydroxide nanosheets for enhanced electrochemical oxidation of water

How to develop cost-effective electrocatalysts for the oxygen evolution reaction (OER) is one of the critical issues in renewable energy storage and conversion technology. Here, we report the preparation of well-ordered ultrathin film (UTF) electrodes based on layered double hydroxide nanosheets (LDH NSs) and iron porphyrin (Fe-PP) through an electrostatic layer-by-layer (LBL) technique, which show excellent OER performance. By virtue of the high catalytic activity of LDH NSs and good electron-transfer ability of Fe-PP, the resulting CoNi-LDH NS/Fe-PP UTF exhibits a remarkably low overpotential (264 mV) to attain an OER current density of 10 mA cm(-2) and a substantially decreased Tafel slope of 37.6 mV dec(-1), much superior to that of the IrO2 catalyst. Moreover, this method can be extended to the preparation of other UTFs based on LDHs and Fe-PP (e.g., CoMn-LDH NS/Fe-PP, CoFe-LDH NS/Fe-PP and ZnCo-LDH NS/Fe-PP) with significantly enhanced OER performance relative to pristine LDH NSs. To illustrate the advantage of these UTFs in practical water splitting, a prototype electrolyzer cell is also fabricated by using the (CoNi-LDH/Fe-PP)(30) UTF as the anode and Pt wire as the cathode, which achieves the production of both oxygen and hydrogen by using a 1.5 V AA battery as the power source.