Temperature Key for RhRu₃Ox in Acidic Water Oxidation

The oxygen evolution reaction is more relevant to your daily life than you would think. It is used in many electrochemical devices, such as batteries. However, this reaction still has a lot of room for improvement that would allow for it to be applied at a larger scale in next-gen technology. To achieve this, researchers at Tohoku University demonstrated an effect that influences the stability of catalysts - the key to making this oxygen evolution reaction more efficient.

The findings were posted in Nature Communications on October 20, 2025.

LSV curves (a), Tafel slope (b) and EIS Nyquist plots (c) of RhRu₃O_x, Hom-RuO₂ and Com-RuO₂. The solution resistance was determined from the intersection of the EIS curve with the real axis when the imaginary part (Z″) equals zero, yielding a value of 25.0 ± 0.4Ω. (d) C₂dl plots calculated from CV curves. (e) Tafel plots of RhRu₃Ox at different temperatures. (f) Arrhenius plot of OER exchange current density of RhRu₃Ox and Hom-RuO₂ CoP. ©Heng Liu et al.

The research team used a home-made operando differential electrochemical mass spectrometry system to examine how RhRu₃O_x behaves in the oxygen evolution reaction. Their findings showed a temperature-dependent mechanism evolution effect, which means that a certain stage of the reaction is triggered by temperature. The revelation of this effect will help researchers understand how to manipulate this pathway in order to create more stable catalysts.

"We found that this catalyst tends towards different reaction mechanisms at high versus low temperatures, which we can now use to our advantage to try and get the outcome that we want," explains Heng Liu (Advanced Institute for Materials Research (WPI-AIMR).

Photograph (a) and Schematic illustration (b) of the operando TC-DEMS set up. Triangular potential applied at room temperature (c) and 60 °C (d) and corresponding MS signal. The upper panel shows the potential (black, left axis) and current density (red, right axis) in relation to time. The lower panel shows the MS signals for ³²O₂ (m/z = 32, orange) and ³⁴O₂ (m/z = 34, blue). The integrated peak area of m/z = 32 (e) and m/z=34 (f) at different cycles and different temperatures. (g) Ratio of peak area of ³⁴O₂: ³²O₂. ©Heng Liu et al.

Since practical implementation is also important, they evaluated the stability of RhRu₃O_x. Remarkably, it remained stable for over 1000 hours at room temperature (current density: 200mA cm⁻²).

To advance this research further, future work should focus on optimizing the F doping levels to systematically enhance catalytic performance and durability under commercial-scale PEM electrolyzer conditions.

This work represents considerable advancement in the fundamental research of TMPs-based hydrogen evolution reaction (HER) catalysts, which paves the way for the rational design of novel highly-efficient, non-noble metal-based cathodes for commercial applications. These catalysts hold tremendous potential as a way to help reduce our reliance on fossil fuels and generate energy in an environmentally-friendly manner.

Calculated 1D surface Pourbaix diagram as a function of potential vs. RHE (pH 1; temperature=298.15 K) (a) and 2D surface Pourbaix diagram as a function of potential vs. SHE and pH (temperature: 298.15 K) (b) of RuO₂ (110). AEM and LOM OER mechanisms illustration (c) and relevant free energy diagrams of these two mechanisms on RhRu₃O_x and undoped RuO₂ (d). ©Heng Liu et al.

Publication Details:
Title: Temperature-dependent mechanism evolution on RhRu3Ox for acidic water oxidation
Authors: Ming-Rong Qu, Heng Liu, Si-Hua Feng, Xiao-Zhi Su, Jie-Xu, Heng-Li Duan, Rui-Qi Liu, You-Qi Qin, Wen-sheng Yan, Sheng Zhu, Rui Wu, Hao Li, Shu-Hong Yu
Journal: Nature Communications
DOI: https://doi.org/10.1038/s41467-025-64286-1

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