Optimized Pt-Co Alloy Nanoparticles for Reverse Water-Gas Shift Activation of CO2.

ABSTRACT

Different Co contents were used to tune bimetallic Pt-Co nanoparticles with a diameter of 8 nm, resulting in PtCo ratios of 3.54, 1.51, and 0.96. These nanoparticles were then applied to the MCF-17 mesoporous silica support. The synthesized materials were characterized with HR-TEM, HAADF-TEM, EDX, XRD, BET, ICP-MS, in situ DRIFTS, and quasi in situ XPS techniques. The catalysts were tested in a thermally induced reverse water-gas shift reaction (CO2H2 = 14) at atmospheric pressure in the 200-700 °C temperature range. All bimetallic Pt-Co particles outperformed the pure Pt benchmark catalyst. The nanoparticles with a PtCo ratio of 1.51 exhibited 2.6 times higher activity and increased CO selectivity by 4% at 500 °C. Experiments proved that the electron accumulation and alloying effect on the Pt-Co particles are stronger with higher Co ratios. The production of CO followed the formate reaction pathway on all catalysts due to the face-centered-cubic structure, which is similar to the Pt benchmark. It is concluded that the enhanced properties of Co culminate at a PtCo ratio of 1.51 because decreasing the ratio to 0.96 results in lower activity despite having more Co atoms available for the electronic interaction, resulting in the lack of electron-rich Pt sites.