Constructing high coordination number of Ir-O-Ru bonds in IrRuOx nanomeshes for highly stable acidic oxygen evolution reaction

Abstract

IrRu bimetallic oxides are recognized as the promising acidic oxygen evolution reaction (OER) catalysts, but breaking the tradeoff between their activity and stability is an unresolved question. Meanwhile, addressing the issues of mass transport obstruction of IrRu bimetallic oxides under high current remains a challenge for the development of proton exchange membrane water electrolysis (PEM-WE). Herein, we prepared an IrRuOx nanomeshes (IrRuOx NMs) with high coordination number (CN) of Ir-O-Ru bonds in a mixed molten salt with high solubility of the Ir/Ru precursor. X-ray absorption spectroscopy analysis revealed that the IrRuOx NMs possess high coordination number of Ir-O-Ru bonds (CNIr-O-Ru = 5.6) with a distance of 3.18 Å. Moreover, the nanomesh structures of IrRuOx NMs provided hierarchical channels to accelerate the transport of oxygen and water, thus further improving the electrochemical activity. Consequently, the IrRuOx NMs as OER catalysts can simultaneously achieve high activity and stability with low overpotential of 196 mV to reach 10 mA·cm−2 and slightly increase by 70 mV over 650 h test. Differential electrochemical mass spectrometry tests suggest that the preferred OER mechanism for IrRuOx NMs is the adsorbent evolution mechanism, which is beneficial for the robust structural stability.