Cooperative effect of bimetallic MOF-derived CoNi(OH) 2 @NiCo 2 S 4 nanocomposite electrocatalysts with boosted oxygen evolution activity.

Highly efficient and inexpensive electrocatalysts for oxygen evolution reaction (OER) are extensively studied for water splitting. Herein, a unique bimetallic nanocomposite CoNi(OH) 2 @NiCo 2 S 4 nanosheet arrays derived from metal-organic-frameworks (MOFs, CoNi-ZIF) is simply fabricated on Ni foam, endowing large specific surface area and outstanding electrical conductivity. Compared with their single-metallic counterparts, the bimetallic composite displays dramatically low overpotential and small Tafel slope as well as outstanding catalytic stability. The overpoptential at 20 mA cm -2 for CoNi(OH) 2 @NiCo 2 S 4 is only 230 mV in comparison with Ni(OH) 2 @Ni 3 S 2 (266 mV), Co(OH) 2 @Co 3 S 4 (294 mV) and RuO 2 ( η  = 302 mV). First-principle calculations based on density functional theory (DFT) are carried out and reveal that the introduction of Ni in Co(OH) 2 helps lowered the energy difference of Δ G OOH* -Δ G O* , and thereby boosting the OER reactivity. This study provides an effective approach for the rational construction of low-cost metal hybrids.