In-situ construction of Mn-doped RuTiO_x nanoarray via template-directed replacement reaction for highly efficient and...

Ruthenium (Ru)-based oxides are promising acidic oxygen evolution reaction (OER) electrocatalysts for proton exchange membrane water electrolysis (PEMWE). Nevertheless, their practical deployment is hindered by the Ru over-oxidation/dissolution in harsh acidic operating environment and binder-induced inferior charge/mass transport in conventional membrane electrodes. Herein, we report a template-directed replacement reaction strategy to in-situ fabricate a manganese (Mn)-doped Ru-Titanium (Ti) oxides solid solution nanoarray on porous Ti felt (Mn-RuTiO_x/TF). The pre-electrodeposited MnO₂ nanosheet array acts as both structural template and Mn source, while the Ti felt (TF) serves as self-supporting electrode and in-situ Ti source for RuTiO_x formation. Combined experimental and theoretical results reveal that the binder-free Mn-RuTiO_x/TF electrode exhibits excellent corrosion resistance to acidic OER conditions, superior conductivity for swift electron movement, and 3D porous network for accelerated mass transport. Meanwhile, homogeneous Mn doping precisely modulates the electronic configuration of RuTiO_x, which mitigates Ru over-oxidation to enhance long-term stability, optimizes the adsorption free energy of the rate-determining *OOH intermediate, and reduces the energy barrier associated with adsorbate evolution mechanism (AEM) pathway. Accordingly, Mn-RuTiO_x/TF anode electrode delivers outstanding acidic OER activity with an overpotential of 184 mV to deliver 10 mA·cm^-2, and maintains stable operation for 200 h at 500 mA·cm^-2 in a practical PEMWE. This work provides a novel integrated regulation strategy for advanced acidic OER electrocatalysts toward practical PEMWE applications.