Enhanced NH3 decomposition for H2 production over bimetallic M(M=Co, Fe, Cu)Ni/Al2O3

Abstract

Ammonia (NH3) has been regarded as an attractive energy source for hydrogen production via catalytic decomposition, especially over non-noble metal catalysts. Owing to the decent performance and low cost, nickel (Ni) based catalysts have been widely studied for catalytic decomposition of NH3 where the decomposition rates, can be further tailored by adding other metals. Herein, we synthesized bimetallic M(M = Co, Fe, Cu)Ni/Al2O3 catalysts delivering superior catalytic performance at a wide temperature range of 350–750 °C. Co-Ni/Al2O3 demonstrated nearly 100% conversion of NH3 decomposition to H2 at 700 °C and the gas hourly space velocity of 30,000 ml g−1 min−1, which was ~20.85% higher than that of intrinsic Ni/Al2O3. The structural characterizations indicated that Co could decrease the particle size and enhance the dispersion of active sites. The density functional theory calculations substantiated that the associative decomposition of N to generate N2 was the rate-determining step of the NH3 decomposition reactions. NH3 Temperature Programmed Desorption (TPD) results suggested that the enhanced catalytic performance was predominantly attributed to the Co that decreases the energy barrier for the associative decomposition of N to form N2. This study provides new insights in designing diverse catalysts for efficient NH3 decomposition for controllable H2 production.