Pd/Cu単原子合金触媒によるCO₂の水素化：放射光XPSとDFT計算による研究

抄録

The surface chemistry of formic acid and the CO₂ hydrogenation process on the Pd/Cu(111) single atom alloy surface was investigated using synchrotron-radiation X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. High-resolution XPS revealed that the decomposition process of formic acid on Pd/Cu(111) is almost identical to that on Cu(111). Density functional theory calculations showed that the indirect charge transfer from Pd to monodentate formate species through the Cu substrate, which causes the considerable chemical shift in Pd 3d_5/2. In addition, it was found that formate species are preferably adsorbed on the Cu site rather than the Pd site, implying the advantage of Pd/Cu(111) in methanol synthesis. Ambient pressure XPS (AP-XPS) demonstrated that hydrogen spillover drives CO₂ hydrogenation into formate and methoxy species even at room temperature. Semi-quantitative analysis of AP-XPS spectra proposed that carbonate acts as a reactive intermediate in methanol synthesis.