Synthesis of methanol from carbon dioxide is among the key goals for net-zero-CO2 production of chemicals and fuels. Previous investigation has suggested that indium oxide could serve as an effective catalyst for this reaction, but the structural details of the indium atoms and of the catalyst support material heavily influence the conversion efficiency of CO2 and the product selectivity for methanol.
Researchers at ETH-Zurich (www.ethz.ch) developed a catalyst that more efficiently converts CO2 to methanol while maximizing the effect of scarce indium. The ETH-Zurich team, led by catalyst engineering professor Javier Pérez-Ramírez, used a single-atom architecture where isolated indium atoms are anchored onto the surface of a specially designed support structure. Informed by prior studies, the research team hypothesized that an effective support material for the In2O3 should combine a set of three structural and electronic characteristics. They arrived at monoclinic hafnium oxide (HfO2) as a material that fit the profile.
Using flame-spray pyrolysis (FSP), the team was able to create catalytic indium-oxide nanostructures with different sizes, including of single-atom active sites. Experiments with three forms of In2O3 (nanoparticles, two-dimensional sheets and single atoms) revealed that the single-atom indium was the most effective structure for the catalyst, but also revealed that the support material was critical.
The HfO2 “unlocks superior methanol productivity in In2O3 systems, breaking a decade-long stagnation in catalyst design,” the researchers say. “This promotional effect reflects improved indium utilization, where indium single atoms anchored on the support surface act as highly efficient hydrogenation centers.”