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 highlyefficient hybrid electrocatalysts containing non-noble metals/alloysand heteroatom-doped carbon through simple, inexpensive, andsmart strategies are highly attractive and prominent for the overallwater splitting. Herein, by choosing waste grapefruit peel as carbonsource and reducer, a convenient and straightforward impregnation-pyrolysis strategy was used to fabricate two series of compositescontaining nitrogen doped carbon-encapsulated NiFe alloys andnitrogen-doped graphitized carbon substrates (NiFe@NC/NGC)under different pyrolysis temperatures and Ni/Fe ratios. Whenevaluated as electrocatalysts for oxygen evolution reaction (OER)and hydrogen evolution reaction (HER) in 1.0 M KOH media, theoptimal catalyst delivers low overpotentials of 287 mV for OER at50 mA cm-2and 190 mV for HER at 20 mA cm-2. The density functional theory calculations reveal that the hollow sites containingtwo Ni atoms and two Fe atoms are dominantly catalytic centers for OER and HER activities of NiFe alloys