Nanostructured hybrid NiFeOOH/CNT electrocatalysts for oxygen evolution reaction with low overpotential

Abstract

Oxygen evolution reaction (OER) has been recognized as a crucial half-reaction in water splitting for the production of hydrogen, one of the most important clean energies. In this article, we report the synthesis of a series of Ni-based NiMOOH layered double hydroxide (LDH, M = Cr, Fe, Co) nanosheets with sizes of about 20 nm with tetramethylammonium hydroxide (TMAOH) as a base source under mild reaction conditions. NiFeOOH shows much lower onset potential than NiCoOOH, NiCrOOH and Ni(OH)₂ in alkaline solution. To further improve the OER activity, NiMOOH/CNT hybrid composites was prepared by in situ addition of carbon nanotubes (CNT) during the synthesis process of NiMOOH. The hybrid composites afford much higher activity than NiMOOH alone, especially for NiFeOOH/CNT with the overpotential of 278 mV at 10 mA cm⁻² in alkaline solution. The significantly improved OER activity of NiMOOH/CNT hybrid composites is mainly attributed to the synergetic effect of CNT and nanostructured NiMOOH by improving the electric conductivity and increasing the exposure degree of active sites for OER. Moreover, the hybrid composites also possess high stability for a prolonged testing time.