Pd0–Ov–Ce3+ Interfacial Sites with Charge Redistribution for Enhanced Hydrogenation of Methyl Oleate to Methyl Stearate

Abstract Improving the efficiency of metal/reducible metal oxide interfacial sites for hydrogenation reactions of unsaturated groups (e.g., C=C and C=O) is a promising yet challenging endeavor. In our study, we developed a Pd/CeO 2 catalyst by enhancing the oxygen vacancy (O V ) concentration in CeO 2 through high-temperature treatment. This process led to the formation of an interface structure ideal for supporting the hydrogenation of methyl oleate to methyl stearate. Specifically, metal Pd 0 atoms bonded to the O V in defective CeO 2 formed Pd 0 –O V –Ce 3+ interfacial sites, enabling strong electron transfer from CeO 2 to Pd. The interfacial sites exhibit a synergistic adsorption effect on the reaction substrate. Pd 0 sites promote the adsorption and activation of C=C bonds, while O V preferably adsorbs C=O bonds, mitigating competition with C=C bonds for Pd 0 adsorption sites. This synergy ensures rapid C=C bond activation and accelerates the attack of active H* species on the semi-hydrogenated intermediate. As a result, our Pd/CeO 2 -500 catalyst, enriched with Pd 0 –O V –Ce 3+ interfacial sites, demonstrated excellent hydrogenation activity at just 30 °C. The catalyst achieved a Cis–C18:1 conversion rate of 99.8% and a methyl stearate formation rate of 5.7 mol/(h·g metal ). This work revealed the interfacial sites for enhanced hydrogenation reactions and provided ideas for designing highly active hydrogenation catalysts.