Catalysis Sciences & Engineering, Short talk
CE-024

Single atoms of indium on hafnia enable superior CO2-based methanol synthesis

Y. Chiang1,2, M. Ritopecki3, P. O. Willi1,2, K. Raue1,2, J. Morales-Vidal3, T. Zou1,2, M. Agrachev1,2, H. Eliasson4, J. Wang1,2, R. Erni4, W. J. Stark1,2, G. Jeschke1,2, R. N. Grass1,2, N. López3, S. Mitchell1,2, J. Pérez-Ramírez1,2*
1ETH Zurich, 2NCCR Catalysis, 3ICIQ, 4EMPA

Green methanol synthesis via CO2 hydrogenation is a promising route to reduce the footprint of chemical and fuel production. While traditional copper-based catalytic systems are highly active, they often suffer from low selectivity and poor stability under CO2-rich conditions. Since the discovery of indium oxide (In2O3) as a highly selective and stable alternative, its combination with monoclinic zirconia (m-ZrO2) support has stood out as a benchmark system, and no other oxide carrier has matched its promotional effect.[1] Detailed mechanistic studies suggested that distinct interfacial geometric and electronic interactions govern the exceptional performance and outstanding stability.[1,2]

Here, we show that monoclinic hafnia (m-HfO2), a wide-bandgap dielectrics underexplored in heterogeneous catalysis, can surpass this benchmark. Nanostructured indium-hafnia (InHfOx) systems achieve up to 70% higher indium-specific methanol productivity than indium-zirconia (InZrOx) analogues (Fig. 1a), with the largest gains observed at low In2O3 contents (i.e. 2 wt%), where isolated indium sites dominate (Fig. 1b).[3] High-resolution electron microscopy, kinetic analysis, in-situ X-ray absorption and electron paramagnetic resonance spectroscopy, and density functional theory collectively identify single-atom indium sites as the predominant active species. Crucially, m-HfO2 provides enhanced surface structural stability and mediates redox potential of indium single atoms, enabling a cooperative surface hydride-proton reservoir that promotes CO2 activation and formate hydrogenation through its wide bandgap (Fig. 1c). Extending beyond In2O3, we show the promotional effect of m-HfO2 could be translated into gallium- and zinc oxides via a dual-site mechanism, where the metal centres and support activate H2 and CO2, respectively. Our findings establish m-HfO2 as a powerful support for advancing CO2-based methanol synthesis, broadening design principles by coupling single-atom catalysis and wide bandgap dielectrics engineering. 

[1] O. Martin et al., Angew. Chem. Int. Ed., 2016, 55, 6261. 

[2] T. P. Araújo, S. Mitchell, J. Pérez-Ramírez, Adv. Mater., 2024, 36, 2409322.  

[3] Y.-T. Chiang et al., Nat. Nanotechnol., 2026, 21, 588.