Promotional role of NiCu alloy in catalytic performance and carbon properties for CO2-free H2 production from thermocatalytic decomposition of methane

Abstract

Thermocatalytic decomposition (TCD) of methane produces CO2-free hydrogen and valuable co-product, solid carbon. In this study, a series of NiCu/CNT catalysts, prepared with varying Ni/Cu metal ratios and synthesis methods, were evaluated for methane TCD performance at various temperatures. Catalysts before and after reaction, and properties of the carbon product, were characterized to identify activity-structure relationships. At 550 °C, a 10 wt% Ni/CNT catalyst was active; however, it deactivated within 1 h of reaction at >600 °C. The addition of Cu increased its stability. At temperatures above 650 °C, only the catalyst with Cu loadings above 10 wt% remained active and stable. Catalyst characterization revealed that changes in i) Ni/Cu ratio, ii) metal particle size, and iii) operating temperature are key factors for TCD activity, stability, and carbon coproduct morphology. The carbon co-product is mainly composed of multiwalled carbon nanotubes (MWCNTs) whose morphology changes with Ni/Cu ratio and reaction temperature.