Synergic effects enhance the catalytic properties of alpha-Ni(OH)2-FeOCPc@rGO composite for oxygen evolution reaction

Abstract

The effect of size and degree of crystallinity, and the synergic interaction of α-Ni(OH)2 nanoparticles (α-Ni) with reduced graphene oxide (rGO) and octacarboxyphthalocyaninate iron(II) (FeOCPc), on the electrocatalytic activity for the oxygen evolution reaction (OER) are demonstrated using structurally well-defined nanocomposite materials. Larger and crystalline α-Ni@rGO-K nanoparticles (4.7 ± 1.8 nm) generated materials with higher activity than the respective α-Ni(OH)2Na derivatives (1.8 ± 0.3 nm), where the incorporation of rGO improved dramatically the performance. However, an even larger efficiency was achieved when α-Ni@rGO-K was covered up with a controlled amount of FeOCPc, a poor molecular OER catalyst, in this way demonstrating a synergic effect of that macrocycle on the reaction kinetics decreasing further the overpotential of the oxygen evolution reaction. In fact, α-NiFeOCPc@rGO-K was the ternary composite material with best performance, being able to sustain a stable current of 10 mA cm−2 during 8 h of continuous electrolysis at 1.64 V vs RHE, in 1.0 mol dm−3 KOH solution, showing good perspectives as electrode material for OER.