Synergistic niobium and manganese co-doping into RuO₂ nanocrystal enables PEM water splitting under high current.

Abstract

Low-cost ruthenium-based catalysts with high activity have emerged as promising alternatives to iridium-based counterparts for acidic oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWE), but the poor stability under high current density remains as a key challenge. Here, we utilize the synergistic complementary strategy of introducing earth-abundant Mn and Nb dopants in ruthenium dioxide (RuO₂) for Nb_0.1Mn_0.1Ru_0.8O₂ nanoparticle electrocatalyst that exhibits a low overpotential of 209 mV at 10 mA cm^-2 and good stability of > 400 h at 0.2 A cm^-² in 0.5 M H₂SO_4. Significantly, a PEMWE device fabricated with Nb_0.1Mn_0.1Ru_0.8O₂ anode can operate continuously at least for 1000 h at 0.5 A cm^-2 with 59 μV h^-1 decay rate. Operando Raman spectroscopy analysis, differential electrochemical mass spectroscopy measurements, X-ray absorption spectroscopy analysis and theoretical calculations indicate that OER reaction on Nb_0.1Mn_0.1Ru_0.8O₂ primarily follows the adsorbate evolution mechanism with much favorable energy barrier accompanied by a locally passivated lattice oxygen mechanism (AEM-LPLOM) and the co-existed Nb and Mn in RuO₂ crystal lattice could not only stabilize the lattice oxygen, but also relieve the valence state fluctuation of Ru site to stabilize the catalyst during the reaction.