Thermally Prepared Mn₂O₃/RuO₂/Ru Thin Films as Highly Active Catalysts for the Oxygen Evolution Reaction in Alkaline Media

Abstract

Herein, a thermal decomposition method was utilised to fabricate pure and mixed manganese and ruthenium oxides as catalysts for the oxygen evolution reaction (OER). X‐ray photoelectron spectroscopy (XPS) and X‐ray diffraction (XRD) reveal the manganese and ruthenium species produced at an annealing temperature of 600 °C to be Mn2O3 and RuO2/Ru, respectively. A number of the mixed Mn/Ru oxides exhibit overpotential values approximately 200 mV lower than previously reported for Mn2O3/RuO2 oxides (at a current density of 10 mA cm−2) for the OER, whereas the Mn 50 material exhibits similar overpotentials reported in the literature for RuO2. Turnover frequency (TOF) numbers for the Mn/Ru oxides were also calculated, and the results show that the TOF values for some of the materials in this work are higher than RuO2. XPS analysis indicates a change in chemical environment of the Mn/Ru materials, which exhibit higher TOF values. Subsequently, the pure Ru 100 material used in this study has a lower overpotential at 10 mA cm−2, as compared to previously reported values in the literature for RuO2 in alkaline media. This may be attributed to the presence of metallic Ru found in the film or the decrease in crystallite size, as determined by XRD. XPS analysis was also carried out after the OER to help determine the order of activity of the materials in this work.

Isolation and Study of Ruthenium–Cobalt Oxo Cubanes Bearing a High-Valent, Terminal RuV–Oxo with Significant Oxyl Radical Character

“…The incorporation of Ru into heterometal oxides or hydroxides (e.g., Mn, 29 Co, 30,31 Ni 32 ) often results in superior catalytic oxidation activity, which suggests a significant influence of metal-metal cooperative effects in this chemistry. Such synergism is also observed in nature where water oxidation by the oxygen-evolving complex (OEC) in photosystem II, a [Mn 4 CaO 5 ] oxo cluster, involves the cooperative accumulation of redox equivalents to access formally high oxidation states and metal-oxo/oxyl species.…”

A mechanical, high surface area and solvent-free ‘powder-to-electrode’ fabrication method for screening OER catalysts

“…As a consequence, the majority of the OER work focuses on the identification of materials that exhibit a low OER overpotential with high stability and are either less expensive earth-abundant materials, or an amalgamation of the latter with a small amount of PGM oxide. [1,[10][11][12][13][14] Obviously, due to the extensive number of possible material candidates for the OER, a rapid screening method is required. Currently, OER studies involve the routine fabrication of electrodes from powders by depositing them onto conducting substrates by various methods, listed in Table 1, and the most popular of which is by drop-casting a dispersion of the metal oxide under investigation onto a glassy carbon, GC, electrode.…”

Mn-Doped Highly Dispersed RuO2 Catalyst with Abundant Oxygen Vacancies for Efficient Decarboxylation of l-Lysine to Cadaverine

“…After peak fitting, three peaks were found at the binding energy of 642.1 eV, 643.9 eV, and 646.0 eV, which were assigned to Mn­(IV), Mn­(VI), and Mn­(VII), respectively, according to the reported studies. − The high-resolution spectra of XPS for Ru 3p with Ru/Beta and Ru–Mn/Beta were shown in Figure c. For Ru/Beta catalyst, two characteristic binding energies of RuO 2 for Ru 3p 3/2 and Ru 3p 1/2 were found at 463.1 and 485.3 eV, respectively. − After curve fitting, two shoulder peaks at 465.3 and 487.5 eV were observed adjacent to those two main peaks. In the study of ref , it was ascribed to the satellite structure of RuO 2 .…”

“…It has been reported that the Mn element had a lower electronegativity (the Pauling electronegativity is 1.55) than that of Ru (the Pauling electronegativity is 2.20). 46 After the successful insertion of Mn into the RuO 2 lattice to form the O−Mn−O−Ru−O structure, O atoms are inclined to get an electron from Mn rather than Ru, leading to a higher electron density at Ru sites. 15,47 The high-resolution O 1s spectra for Ru/Beta and Ru−Mn/ Beta were depicted in Figure 7.…”