Enhancing the Activity of CO2 Hydrogenation to Methanol Catalysts by Controlling the Precipitant to Promote the "Fence-Fixed" Structure.

Abstract

CO2 hydrogenation to methanol is a promising way to realize carbon neutrality. As the most widely investigated catalysts, Cu-Zn-Al prepared by coprecipitation method exhibited excellent performance. In this work, a series of Cu-Zn-Al catalysts were prepared by using Na2CO3, NaOH, and their mixture as precipitants. The effects of precipitants on the physicochemical properties and catalytic performance were systematically investigated. The results show that the catalyst prepared with the mixture of Na2CO3 and NaOH as precipitants yields a moderately-ordered Cu-Zn-Al layered double-hydroxide (LDH) precursor with moderate grain size. After calcination and reduction, the catalyst exhibits a "fence-fixed" structure: Cu-rich domains spatially interspersed and separated by Zn/Al-containing oxide regions. This structure constructs abundant heterogeneous interfaces and forms a strong Cu-ZnO electronic interaction, which is favorable for CO2 and H2 adsorption but unfavorable for the adsorption of H2O in the product. Consequently, the sample exhibited the highest CO2 conversion and methanol selectivity. The catalytic performance remains stable after testing at relatively high temperature. The above results provide a theoretical basis and practical reference for the development of efficient and stable Cu-Zn-Al catalysts for CO2 hydrogenation to methanol.