Enhanced CO₂ hydrogenation to methanol over CuZn nanoalloy in Ga modified Cu/ZnO catalysts

With the introduction of Ga³⁺ into Cu/ZnO catalyst precursors, a series of catalysts have been prepared using a simple co-precipitation method and tested as catalysts for the synthesis of methanol from CO₂ hydrogenation. It is found that the presence of a small amount of Ga³⁺ can facilitate thermal deep reduction of ZnO support to Zn atoms under hydrogen prior to catalysis; hence, a highly active CuZn bimetallic nanoparticle offering catalytic sites is generated. The effect of Ga³⁺ incorporation is attributed to the formation of Ga-containing spinel, ZnGa₂O₄ structure, which creates electronic heterojunction with excess ZnO phase to account for the facilitated reduction of Zn²⁺ to Zn⁰ to form CuZn when in contact with Cu nanoparticle. A correlation between Zn⁰ concentration in the CuZn alloy nanoparticle to the catalytic performance can thus be clearly demonstrated, which shows CO₂ conversion and methanol selectivity can be significantly improved by increasing the Zn⁰ content in these hetero-junctioned catalysts.