Tailoring CuFeOx-Based Catalytic Oxygen Carrier for Lattice Oxygen-Induced Oxidative Steam Reforming of Methanol.

Abstract

Methanol reforming demonstrates the possibility of realizing hydrogen storage, transport, and on-site supply. Nevertheless, this approach faces limitations due to outlet CO generation and catalyst degradation. This work fabricates a series of CuFeO_x-based catalytic oxygen carriers (COC) with various Cu-to-Fe ratios for lattice oxygen-induced methanol reforming, which goes through lattice oxygen-induced methanol reforming  →  catalytic steam methanol reforming → oxidative steam methanol reforming. It is revealed that the lattice oxygen mobility can be tuned by modulating the Cu-to-Fe mole ratios. Of the synthesized COCs, Cu₂Fe₃ shows the highest catalytic activity. It is supposed that CuO in COC provides lattice oxygen with catalytically site of Cu⁰, while CuFe₅O₈ contributes relatively stable Cu⁺, synergistically inducing highly efficient oxidative steam reforming of methanol. Specifically, a H₂ production rate of 93.9 mmol·H₂·h^-1 g^-1·COC·at 220 °C is achieved with relatively stable redox looping within 20 cycles. The in situ diffuse reflectance infrared Fourier transform spectroscopy results indicate that the bridged formate species is identified as the primary intermediate under lattice oxygen-induced conditions, and the reaction pathway is anticipated to be CH₃OH* → CH₃O* → CH₂O* → HCOO* → H₂ + CO₂.