Compatibility of NiO/CuO in Ca–Cu Chemical Looping for High-Purity H₂ Production with CO₂ Capture

Ca–Cu chemical looping is a novel and promising approach for converting methane into pure H₂ following the principle of sorption-enhanced reforming. Its operational efficiency is largely determined by an appropriate coexistence of Cu-based oxygen carriers and Ni-based catalysts. Here, NiO/CuO composites are synthesized and their catalytic activity for H₂ production is measured using a fixed-bed reactor system equipped with an online gas analyzer. It is reported that the presence of CuO can hinder the activity of Ni-based catalysts in H₂ production, and experimental results show that the negative effect of CuO is strengthened with increasing CuO content and calcination temperature during sample preparation. With the help of a series of specific test and characterization techniques, interaction rules between NiO and CuO are further investigated and understood, and based on that an action mechanism model is proposed. Furthermore, an arrangement of mixed particles that avoids the intimate contact of CuO/NiO is suggested and tested, and a superior performance is demonstrated while observing no restrictions of CuO on Ni-based catalysts in sorption-enhanced steam-methane reforming under the conditions of Ca–Cu chemical looping.