Probing Changes in the Local Structure of Active Bimetallic Mn/Ru Oxides during Oxygen Evolution

Abstract

Identifying the active site of catalysts for the oxygen evolution reaction (OER) is critical for the design of electrode materials that will outperform the current, expensive state-of-the-art catalyst, RuO2. Previous work shows that mixed Mn/Ru oxides show comparable performances in the OER, while reducing reliance on this expensive and scarce Pt-group metal. Herein, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) are performed on mixed Mn/Ru oxide materials for the OER to understand structural and chemical changes at both metal sites during oxygen evolution. The results show that the Mn-content affects both the oxidation state and local coordination environment of Ru sites. Operando XAS experiments suggest that the presence of MnO x might be essential to achieve high activity likely by facilitating changes in the O-coordination sphere of Ru centers.

Wrinkled Ir-MnOx nanospheres as pH-universal electrocatalysts for oxygen evolution reaction

“…36 Compared with Mn 2 O 3 , a mixed Mn 2+ /Mn 3+ oxidation state exists in Ir-MnO x , which can accelerate the charge transfer 55 and confer greater coordination flexibility around the Ir sites. 56,57 Besides, in the high-resolution Ir 4f XPS spectrum (Fig. 2d) of Ir-MnO x , the peaks at binding energies of 61.7 and 64.6 eV can be assigned to Ir 4f 7/2 and Ir 4f 5/2 of metallic Ir.…”

High-Stability RuO2/MoO3 Electrocatalyst for the Oxygen Evolution Reaction in Proton-Exchange-Membrane Water Electrolysis

“…Hydrogen, with its exceptional energy conversion efficiency, high energy density, and zero carbon emissions, holds great promise as novel energy future. − PEM water electrolysis offers numerous advantages, including high current density, excellent energy efficiency, and a compact design. − However, the oxygen evolution reaction (OER), which is a crucial half-reaction in PEM water electrolysis, presents significant challenges due to its high energy barrier. − The iridium and ruthenium combined catalysts have been the most common catalysts for the oxygen evolution reaction (OER) for PEMWE. Especially, iridium-based catalysts have been extensively studied due to their exceptional stability. − However, the high cost and limited reserves of iridium hinder the commercialization of PEM electrolyzes. , Ruthenium (Ru) with better OER activity, higher abundance, and lower cost is considered a suitable candidate catalyst. − However, a Ru-based catalyst exhibits poor stability under harsh acidic and anodic conditions. ,,, Therefore, high-stability Ru-based catalysts without Ir are potential cost-effective catalysts. ,, Lin et al developed Ru/MnO 2 and Ru/TiO 2 , both revealing outstanding long-term durability. , Therefore, an appropriate support for ruthenium-based catalysts may be an effective method to enhance catalyst stability due to the strong interaction between the metal with supports.…”