Solar-driven chemical looping dry reforming of methane: Ni modification of pyrochlore-fluorite oxygen carriers

Solar-driven chemical looping dry reforming of methane (solar-driven CLDRM) aims at utilizing renewable energy for syngas production. In this study, Ni is incorporated in the pyrochlore-fluorite oxygen carriers (OCs) to reduce the temperature and enhance the performance of OCs. Experimental results show that the OC with 5 wt% Ni loading favors CLDRM at 700 °C, while LCNZ-10 wt% enables efficient solar-driven CLDRM at 600 °C. This demonstrates that Ni substitution with photo-response in the chemical looping process significantly reduces the reaction temperature compared to conventional catalytic DRM (900 °C). In addition, characterizations including XRD, Raman, XPS, UV-Vis, EIS, PL/TRPL, and TEM provide an overall perspective for understanding the effect of Ni particle dispersion on the stability, oxygen-ion conductivity, oxygen capacity, and redox cycling performance of OCs. The results demonstrate the potential of Ni-substituted pyrochlore-fluorite OCs in the application of solar-driven CLDRM. • LCNZ-5wt favors CLDRM at 700 °C, while LCNZ-10wt enables efficient solar-driven CLDRM at 600 °C. • The monolayer dispersion threshold of the Ni species in pyrochlore-fluorite support governs the formation of Ni nanoparticles. • The SMSI effect between Ni and the support is driven by lattice incorporation in pyrochlore and oxygen vacancy formation in fluorite. • Ni modification broadens sub‑bandgap photon absorption via Ni 2+ d-d transitions and NiO x defect states.