Ru-Doped Pd Nanoparticles for Nitrogen Electrooxidation to Nitrate

Electrocatalytic nitrogen oxidation to nitrate is a promising alternative to the conventional nitrate synthesis industry, which is accompanied by huge energy consumption and greenhouse gas emission. However, breaking the N≡N triple bond (941 kJ·mol–1) in nitrogen is still challenging, and thus, the development of efficient electrocatalysts with established reaction pathways is highly required. Herein, a series of Ru-doped Pd materials are prepared, and the optimized Pd0.9Ru0.1 sample exhibits superior performance for electrocatalytic nitrogen oxidation into nitrate, greatly outperforming pure Pd and Ru samples. The 15N isotope-labeling studies and other characterizations results indicate that the produced nitrate originates from N2 electrooxidation. Electrochemical in situ Raman spectra reveal the formed Pd0.9Ru0.1O2 on the surface serves as the active species. Electrochemical in situ Fourier transform infrared spectroscopy and online differential electrochemical mass spectrometry experimentally unveil the reaction pathway of nitrogen electrooxidation on Pd0.9Ru0.1O2. The combined results of experiments and theoretical simulations reveal Ru doping not only promotes the formation of more active species but also changes the potential-limiting step with a lower energy barrier.