The role of promoters on NiO catalysts for methane decomposition and hydrogen production

In this study, the impact of Al, Co, and Cu as promoters for NiO to enhance its catalytic performance in methane decomposition has been investigated. The catalysts were synthesized via a co-precipitation route and comprehensively characterized using SEM, BET, XRD, XPS, Raman, TPR, and TGA techniques. Catalytic performance was evaluated in a fixed-bed reactor operated at 800 °C with a feed gas flow rate of 20 mL/min. Al³⁺ and Cu²⁺ incorporation into NiO reduced crystallite size and increased surface area, while Co²⁺ had the opposite effect, indicating a distinct structural impact. Additionally, Al³⁺ doping induced a charge imbalance in NiO, leading to an increase in Ni^2⁺ content and oxygen vacancies, as confirmed by XPS analysis. Catalytic activity tests revealed that Al³⁺ was the most effective promoter for NiO, followed by Co²⁺ and Cu²⁺, respectively. The highest CH₄ conversion rate and H₂ production rate, achieved with 10% Al-NiO at a time-on-stream (TOS) of 25 min, were 71% and 216.2 × 10⁻⁵ mol H₂ g⁻¹ min^{− 1}, respectively. The methane decomposition process exhibited stable operation with minimal CO and CO₂ emissions. The catalytic performance was correlated with the detailed physicochemical properties of both fresh and spent catalysts.