Synergistic niobium and manganese co-doping into RuO2 nanocrystal enables PEM water splitting under high current
Bichen Yuan, Qian Dang, Hai Liu, Marshet Getaye Sendeku, Jian Peng, Yameng Fan, Liang Cai, Aiqing Cao, Shiyao Chen, Hui Li, Yun Kuang, Fengmei Wang, Xiaoming Sun
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 Nb0.1Mn0.1Ru0.8O2 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 H2SO4. Significantly, a PEMWE device fabricated with Nb0.1Mn0.1Ru0.8O2 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 Nb0.1Mn0.1Ru0.8O2 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. Ruthenium-based catalysts for the acidic oxygen evolution reaction under high current exhibit poor stability. Here, authors develop a doped ruthenium oxide nanocrystal, which improves water splitting performance by stabilizing lattice oxygen and limiting the ruthenium site valence oscillation.