Simplified Preparation of BaAl2O4−y e− y /C Oxy-Electrides Using Pechini Approach for Ammonia Synthesis

Abstract

Electride-based materials are among the most active catalysts for ammonia synthesis, with a strong potential for application in the development of green ammonia synthesis; however, their synthesis often requires complicated reaction conditions limiting their scalability. Herein, a straightforward and scalable synthesis method for a BaAl2O4−ye−y/C oxy-electride composite via carboxylic acid complexation (pseudo-Pechini) followed by carbothermal reduction is presented. The resulting composite exhibits significant surface area, of ≈41 m2 g−1, which is considerably higher than the electrides prepared by solid-state synthesis. Upon loading with ruthenium, the BaAl2O4−ye−y/C composite demonstrates excellent catalytic activity for ammonia synthesis, achieving rates of 3090 μmol g−1catalyst h−1 with 0.6Ru/BaAl2O4−ye−y/C, and 3737 μmol g−1catalyst h−1 with 1.1Ru/BaAl2O4−ye−y/C at mild reaction conditions (400 °C and 1 bar). Comprehensive characterization through X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy confirms the textural and structural properties of the catalyst, while iodometric titration method and electron paramagnetic resonance analysis confirm the electride-like nature of the resulting composite. The results reported in this work highlight a straightforward approach for the design of electride-based composite material displaying superior catalytic properties for green ammonia synthesis.