Engineering Efficient NiIrx/CNT Hybrid Nanostructures for pH-Universal Oxygen Evolution

Development of highly efficient and pH-universal oxygen evolution reaction (OER) electrocatalysts with reduced noble metal dosage while enhancing catalytic performance is essential for the commercial application of water electrolyzers. Here, we report the NiIrx/carbon nanotube (CNT) hybrid nanostructures in situ grown on carbon fiber paper (CFP) substrate for efficient OER in wide pH ranges. In 0.5 M H2SO4, the resulting NiIrx/CNT/CFP electrode only demands 196 mV overpotential to achieve 10 mA cm–2, which is significantly superior to those of the Ni/CNTs, Ir/CNTs, and NiIrx samples. Meanwhile, it also shows high performance in alkaline solution with a low overpotential of 220 mV at 10 mA cm–2. The in situ grown approach guarantees the intimate contact between the substrate and the catalyst, and the CNTs provide high conductivity and high exposed surface area for active sites. Furthermore, the introduction of Ni triggered electronic coupling between Ir and Ni that regulates the adsorption energy for the OER intermediates, as indicated by density functional theory calculations. This work demonstrates the cooperative effect not only between the noble metals and the support but also between noble metals and the non-noble metals for the OER.