Hydrogen Adsorption on Pd–In Intermetallic Surfaces

It has recently been shown that CO_2 hydrogenation to methanol over PdIn and In_2O_3 depends critically on the adsorption energy of hydrogen. Here we use density functional theory calculations to investigate hydrogen adsorption over Pd–In intermetallic compound surfaces with different Pd:In ratios. The electronic structure and properties of hydrogen adsorption are investigated for a range of surface facets and compared to the corresponding results for the pure parent metals and Cu. Increased In content is found to shift the Pd( d ) density of states away from the Fermi level, making the intermetallic Pd–In compounds to appear “Cu-like”. We find a linear correlation between the hydrogen binding energy and the d -band center of surface Pd atoms. Understanding of how the hydrogen adsorption energy depends on composition and structure provides a possibility to enhance the performance of CO_2 hydrogenation catalysts to methanol.