> ## Content Index > Fetch the complete content index at: https://research-pop.com/llms.txt > Use this file to discover other available public pages before exploring further. # Northwestern researchers give Mn and Ti complementary roles in durable acidic oxygen evolution - URL: https://research-pop.com/northwestern-researchers-give-mn-and-ti-complementary-roles-in-durable-acidic-oxygen-evolution/ - Published: 2026-10-02T12:53:23.000Z - Updated: 2026-10-02T12:53:23.000Z - Author: ResearchPOP ![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/10/Screenshot-2026-10-02-at-14.36.36.png) Source: [https://doi.org/10.1021/jacs.6c12618](https://doi.org/10.1021/jacs.6c12618?ref=research-pop.com) ## At a glance Can two dopants take different jobs in an oxygen-evolution catalyst? Researchers at Northwestern University and collaborating institutions explore this idea in Ru₀.₇Mn₀.₁Ti₀.₂Oₓ. Their study assigns Mn a redox-active role in tuning reaction-intermediate energetics and buffering changes in Ru, while Ti remains comparatively redox-inert and helps stabilize the oxygen sublattice. The catalyst requires an overpotential of 143 mV at 10 mA cm⁻² and operates for more than 1,000 hours at 0.4 A cm⁻². In a separate proton-exchange-membrane water electrolyser test at 60 °C, it reaches 1 A cm⁻² at a cell voltage of 1.66 V and runs at that current density for 800 hours, with a reported voltage-rise rate of approximately 0.2 mV h⁻¹. The authors connect these results with element-specific operando spectroscopy, isotope-labelled oxygen measurements, in situ Raman spectroscopy and calculations. Together, the measurements follow how the two dopants affect both the working metal sites and the oxygen framework around them. ## Background Water electrolysis couples hydrogen evolution at the cathode with oxygen evolution at the anode. In acidic conditions, the anodic reaction converts water into O₂, protons and electrons. Forming an O–O bond requires several proton- and electron-transfer steps, and the additional potential needed to sustain those steps contributes to the energy demand of the electrolyser. Proton-exchange-membrane water electrolysers place this chemistry in an acidic environment. Their anode catalysts must remain active while exposed to oxidizing potentials and sustained oxygen production. Ruthenium oxides can catalyse oxygen evolution at relatively low overpotential, but maintaining their structure during prolonged operation is a central challenge. Changes in Ru oxidation state and metal–oxygen bonding can accompany reconstruction or dissolution. Two reaction descriptions help frame this problem. In an adsorbate-evolution pathway, oxygen-containing intermediates such as \*OH, \*O and \*OOH form on catalytic sites before O₂ is released. The asterisk denotes a surface-bound species. In a lattice-oxygen pathway, oxygen belonging to the oxide framework participates in the reaction. Lattice participation can provide another route to O–O bond formation, but its relationship with durability depends on how effectively the framework accommodates and repairs the associated changes. Doping can alter both intermediate binding and lattice stability. Those effects need not be supplied by the same element, however. A dopant that improves reaction energetics may also make lattice oxygen more reactive. The researchers address this balance by combining Mn, which can respond through changes in oxidation state, with Ti, intended to reinforce the oxygen framework while remaining comparatively redox-inert. ## Research question Can Mn and Ti coexist in one RuOₓ lattice and retain distinct functions under operating conditions? If so, can their complementary roles account for both low oxygen-evolution overpotential and sustained high-current operation? The team examines this question by comparing undoped, singly doped and dual-doped oxides, then following their electronic and oxygen-related responses during catalysis. A PEM water-electrolyser experiment extends the comparison from catalyst testing to an operating device. ## Inside the study The structural analysis begins with Rietveld-refined X-ray diffraction and electron microscopy. These measurements support a rutile-type oxide with Ru, Mn, Ti and O distributed across the observed particles. The refined lattice parameters are a = b = 4.515 Å and c = 3.058 Å. Ru K-edge spectroscopy shows that dual doping changes the local coordination and places the average Ru valence between those of the Mn-only and Ti-only reference materials. Electrochemical comparisons then separate the activity contributions. At 10 mA cm⁻², RuO₂, the Ti-only oxide, the Mn-only oxide and the dual-doped oxide require overpotentials of 161, 203, 144 and 143 mV, respectively. Mn-only and dual-doped samples thus show nearly identical initial activity, whereas Ti alone does not improve the overpotential relative to RuO₂. The authors associate the activity enhancement primarily with Mn. The complementary contribution becomes clearer during extended operation. The dual-doped catalyst runs for more than 1,000 hours at 0.4 A cm⁻², with a reported potential-rise rate near 173 μV h⁻¹. The study connects this durability with the stabilizing role of Ti while retaining the favourable activity associated with Mn. The catalyst is also tested in a PEM water electrolyser at 60 °C with a Ru loading of 1 mg cm⁻². The cell reaches 1 A cm⁻² at 1.66 V. During an 800-hour test at that current density, the voltage rises by approximately 0.16 V, corresponding to an average increase of about 0.2 mV h⁻¹. This full-cell measurement includes the operating device and is distinct from the catalyst overpotential measured at 10 mA cm⁻². Operando X-ray measurements provide an element-specific view of the proposed division of roles. In the dual-doped material, the estimated average Ru oxidation state changes only slightly, from approximately +3.77 to +3.80\. Under the compared conditions, RuO₂ changes from approximately +3.95 to +4.25\. The smaller shift in the dual-doped sample indicates that its Ru environment undergoes less oxidation during the measurement. Mn responds more visibly, with its estimated average oxidation state increasing from approximately +3.78 to +3.88\. Ti remains close to +4 and retains a comparatively stable coordination environment. The authors interpret these contrasting responses as redox flexibility supplied by Mn alongside structural stabilization supplied by Ti. Rather than requiring Ru to accommodate the full electronic change, the multicomponent oxide distributes that response across its constituents. Isotope-labelled oxygen measurements examine how this electronic behaviour relates to oxygen participation. The reported mixed-isotope fraction is 14.1% for the Mn-only oxide but 4.8% for the dual-doped material. The latter is close to the 4.9% blank and the 5.4% result for RuO₂. Within this comparison, adding Ti suppresses the elevated mixed-isotope signal observed with Mn alone, supporting reduced lattice-oxygen participation under the tested conditions. In situ Raman spectroscopy supplies a complementary observation of surface chemistry. A band assigned to \*OOH appears near 930 cm⁻¹ above 1.6 V. Read alongside the isotope measurements, this signal supports the authors’ account of an adsorbate-mediated pathway in which the dopants tune intermediate energetics while limiting excessive involvement of framework oxygen. The calculations compare the same competing pathways. Along the adsorbate-evolution route, the calculated energetic trend becomes more favourable from RuO₂ to the Mn-only model and then to the dual-doped model. For the lattice-oxygen route, Mn alone lowers the calculated energetic requirement, while adding Ti raises it again toward the RuO₂ reference. These trends are consistent with promoting adsorbate chemistry while restraining lattice-oxygen activation. The combined interpretation brings the measurements together. Mn contributes redox responsiveness and helps adjust the energetics of oxygen-containing adsorbates, including \*OOH. Ti provides a comparatively stable local environment that reduces the lattice-oxygen response introduced by Mn alone. Their roles are complementary: the dual-doped oxide retains the low initial overpotential of the Mn-containing material while supporting extended operation. ## Takeaways and outlook The study presents dual doping as a way to distribute catalytic functions within one oxide. Mn supplies redox flexibility and favourable intermediate energetics, while Ti helps stabilize the oxygen sublattice. The design connects electronic regulation with structural restraint rather than treating activity and durability as independent targets. The catalyst and device experiments follow this idea across different operating conditions: 143 mV overpotential at 10 mA cm⁻², more than 1,000 hours at 0.4 A cm⁻², and 800 hours at 1 A cm⁻² in a PEM water electrolyser at 60 °C. Operando spectroscopy and isotope measurements provide the authors’ explanation for how the material sustains those reactions. The work offers a basis for exploring how complementary dopants can preserve active Ru environments while controlling oxygen reactivity. Lower Ru loading, higher operating current and longer device tests are further directions for developing this design approach. ## About the researchers Jun-Ye Zhang and Yiqing Chen (Northwestern University) and Hsiang-Chun Yu (National Synchrotron Radiation Research Center and National Yang Ming Chiao Tung University) are co-first authors. Ke Xie and Edward H. Sargent (Northwestern University) are the corresponding authors. The other authors are Mengjie Liu, Jaerim Kim, Yongxiang Liang, Bosi Peng, Zeyan Liu, Zedong Zhang and Yong Wang of Northwestern University; Jiashun Liang and Gang Wu of Washington University in St. Louis; Chun-Kuo Peng and Yan-Gu Lin of the National Synchrotron Radiation Research Center and National Yang Ming Chiao Tung University; and Yoon Jun Son of Shell International Exploration and Production Inc. ## Original research Jun-Ye Zhang; Hsiang-Chun Yu; Yiqing Chen; Mengjie Liu; Jaerim Kim; Yongxiang Liang; Bosi Peng; Zeyan Liu; Zedong Zhang; Yong Wang; Jiashun Liang; Gang Wu; Chun-Kuo Peng; Yoon Jun Son; Yan-Gu Lin; Ke Xie; Edward H. Sargent. “Dual-Modulation Strategy in RuOₓ Improves Activity and Durability in Acidic Oxygen Evolution.” *Journal of the American Chemical Society* (2026). Published online 1 October 2026\. DOI: [10.1021/jacs.6c12618](https://doi.org/10.1021/jacs.6c12618?ref=research-pop.com). --- ## Research POP Notes This article reflects the independent interpretation of the Research POP team and does not represent the views of the authors, their institutions or the journal. If you identify any inaccuracies or have concerns regarding the content, figures or attribution, please contact us at [team.researchpop@gmail.com](mailto:team.researchpop@gmail.com). We will review the matter promptly and make corrections or remove the relevant material where appropriate.