LaMnO3 perovskite supported Co–Ni catalysts for efficient ammonia decomposition

Abstract

Ammonia is a promising hydrogen carrier, but its decomposition at low temperatures using cost-effective, non-noble metal catalysts remains a significant challenge. In this work, several catalysts with 50 wt% metal loading on an LaMnO₃ perovskite support were synthesized using a dry mixing method. Various metal ratios were studied, such as 50%CoNi(1 : 1)/LaMnO₃, 50%CoNi(0.5 : 1)/LaMnO₃, 50%Co/LaMnO₃, and their respective 0.5%Ru-incorporated samples. Different characterization techniques, such as XRD, SEM, TEM, and HRTEM, were conducted to evaluate their structural properties. The catalytic performance of these catalysts was investigated in a fixed-bed reactor within a temperature range of 200–700 °C. Initially, monometallic catalysts, 50% Co/LaMnO₃, 50%Ni/LaMnO₃, and 0.5%Ru/LaMnO₃, were tested, and the results showed that 90% ammonia conversion was achieved at 555 °C, 590 °C, and 610 °C, respectively, when reduced at 350 °C. Among the catalysts, the 0.5%Ru–50%CoNi(1 : 1)/LaMnO₃ catalyst showed better activity when reduced at 350 °C, whereas the optimal reduction temperature was 700 °C for the 0.5%Ru–50%Co/LaMnO₃ catalyst. The pre-reduced catalyst 0.5%Ru–50%CoNi(1 : 1)/LaMnO₃ at 350 °C decomposed 95% ammonia at 535 °C with the GHSV of 20 400 mL g⁻¹ h⁻¹. Catalysts 50%CoNi(1 : 1)/LaMnO₃ and 0.5%Ru–50%CoNi(1 : 1)/LaMnO₃ retained their stability over 48 h. The synergies between Co and Ni in the bimetallic system facilitate the transfer of electrons, thereby increasing the active site availability for ammonia molecules.