Engineering oxygen vacancies with atomically dispersed WOx: a strategy for superior CO2 hydrogenation performance and stability on Pd/CeO2

Abstract

The catalytic hydrogenation of CO₂ represents a promising strategy for converting renewable resources into value-added fuels and chemicals, driving the development of highly efficient CO₂ hydrogenation catalysts. In this study, we elucidate the role of atomically dispersed WO_x species in promoting CO₂ hydrogenation over heterogeneous catalysts consisting of atomically dispersed Pd and WO_x species supported on CeO₂. Comprehensive characterization demonstrates that the introduction of atomically dispersed WO_x species enhances the reducibility of the Pd species and increase surface oxygen vacancies (≈40% O_ads. component), strengthening CO₂ adsorption and activation. Under 30 bar, the optimized Pd/0.6WO_x-CeO₂ achieves a methanol space-time yield of 11.9 g_MeOH·g_Pd⁻¹·h⁻¹ at 300 °C, nearly twofold higher than Pd/CeO₂, and maintains performance over 15 h. Kinetic analysis indicates a 29.1 kJ mol⁻¹ decrease in the apparent activation energy for methanol formation (and 22.3 kJ mol⁻¹ for CO at 1 bar), consistent with facilitated H₂ activation and vacancy-mediated CO₂ adsorption. In situ DRIFTS analysis suggests that WO_x modification shifts the dominant surface sequence toward more rapid conversion of carbonate to formate and methoxy species with no detectable bicarbonate intermediate under our DRIFTS conditions, aligning with a vacancy-rich surface. Together, these results support vacancy engineering with atomically dispersed WO_x as a design principle for single-atom Pd catalysts, delivering superior CO₂-to-methanol performance and robust stability under water-producing conditions.