(509g) Mechanistic Understanding of Inverse ZrO2/Cu Catalysts for CO2 Hydrogenation to Methanol

Anthropogenic CO₂ emissions are the major contributor to climate change.[1] Selective CO₂ hydrogenation to methanol using renewable H₂ is a potential solution to mitigate CO₂ emissions and produce value-added liquid fuels. Cu/oxides catalysts have shown promising performance for this reaction, however, due to the stable nature of CO₂ and thermodynamics limitations, highly selective catalysts with excellent low-temperature activity are desirable.[2]

Here, we developed inversed ZrO₂/Cu catalysts to investigate the promotion effect of ZrO₂ overlayers on Cu nanoparticles for the CO₂ hydrogenation to MeOH. Controllable ZrO₂ overlayer thicknesses on Cu were obtained by a sol-gel method. CO₂ conversion over bare Cu nanoparticles is negligible. With 1 wt.% ZrO₂ coating, the MeOH productivity improved significantly and 5 wt.% ZrO₂ can enhance the MeOH productivity further. However, 10 wt. % ZrO₂ leads to lower MeOH yield. The MeOH selectivities are higher than 80% at temperatures ≤ 250 ^oC over all inversed catalysts, while conventional ZrO₂-supported Cu catalysts obtain lower MeOH yield. The diffuse reflectance infrared spectroscopy (DRIFTS) experiment confirmed the absence of intermediate species over bare Cu. When the Cu was modified by ZrO₂ species, we observed formate species formation, suggesting that the methanol formation likely follows the formate pathways, which is consistent with Density Functional Theory (DFT) calculation results. Moreover, only bicarbonate and carbonate species were observed over bare ZrO₂, indicating that the formate species were formed on the interfacial sites of ZrO₂/Cu catalysts.

1. IPCC Sixth Assessment Report, (2021).
2. Jiang, X., Nie, X., Guo, X., Song, C. and Chen, J.G. Rev., 120, 15, 7984-8034, (2020).