Mechanochemical synthesis of Cu-Ni catalysts on Al2O3 and ZnO for steam reforming of methanol

Abstract: A solvent-free mechanochemical (ball-milling) method was employed to synthesize highly efficient bimetallic Cu2Ni1 catalysts supported on Al2O3 and ZnO for methanol steam reforming (MSR) studies. Comprehensive structural and surface analyses (XRD, TEM, BET, H2-TPR, XPS) revealed that this approach reduces crystallite sizes by as much as 83%, induces intimate Cu-Ni atomic mixing, and strengthens metal-support interactions, enabling the formation of highly reducible Cu-Ni solid solutions with a nanoscale domain size of 5-15nm. Among the catalysts, the Al2O3-supported catalyst (Cu2Ni1/Al2O3) exhibited the most superior structural and catalytic properties. Its strong Cu-Ni-Al interfacial bonding evidenced by high-temperature reduction features in H2-TPR and the smallest crystallite size provided exceptional anti-sintering stability, maintaining ≥ 90% methanol conversion and approximately 99% H2 selectivity over 60 hours of continuous reaction at 250 C. This stability mitigated deactivation pathways and restricted the formation of CH4 (methane). Conversely, the ZnO-supported catalyst (Cu2Ni1/ZnO) acted as an excellent promoter for low-temperature reducibility, yielding superior CO2 selectivity of ~97% at 150 C, but showed undesirable methanation at temperatures above 300 C. The observed performance is governed by a bifunctional mechanism where Cu sites drive methanol dehydrogenation, Ni sites activate water for the Water-Gas Shift (WGS) reaction, and the Cu-Ni interface synergistically enhances intermediate oxidation. This work validates mechanochemical synthesis as a facile and green pathway for engineering robust, high-performance Cu-Ni alloy catalysts for sustainable H2 generation.