NiFe Alloys@N-doped Graphene-Like Carbon Anchored on N-Doped Graphitized Carbon as a Highly Efficient Bifunctional Electrocatalyst for Oxygen and Hydrogen Evolution Reactions

The rational design and construction of highly efficient hybrid electrocatalysts containing non-noble metals/alloys and heteroatom-doped carbon through simple, inexpensive, and smart strategies are highly attractive and prominent for the overall water splitting. Herein, by choosing waste grapefruit peel as carbon source and reducer, a convenient and straightforward impregnation-pyrolysis strategy was used to fabricate two series of composites containing nitrogen doped carbon-encapsulated NiFe alloys and nitrogen-doped graphitized carbon substrates (NiFe@NC/NGC) under different pyrolysis temperatures and Ni/Fe ratios. When evaluated as electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 1.0 M KOH media, the optimal catalyst delivers low overpotentials of 287 mV for OER at 50 mA cm–2 and 190 mV for HER at 20 mA cm–2. The density functional theory calculations reveal that the hollow sites containing two Ni atoms and two Fe atoms are dominantly catalytic centers for OER and HER activities of NiFe alloys.