Impact of surface chemistry

Abstract

The applications of molecular surface chemistry in heterogeneous catalyst technology, semiconductor-based technology, medical technology, anticorrosion and lubricant technology, and nanotechnology are highlighted in this perspective. The evolution of surface chemistry at the molecular level is reviewed, and the key roles of surface instrumentation developments for in situ studies of the gas-solid, liquid-solid, and solid-solid interfaces under reaction conditions are emphasized.

Fig. 1.

Annual average of toxic mobile emissions in Los Angeles County from 1975 to 2008. (Source: California Environmental Protection Agency, Air Resources Board. http://www.arb.ca.gov/app/emsinv/emssumcat.php, last date access: 08/10/2010.).

Fig. 2.

(A) The structure of the reconstructed Ir(100) crystal face obtained by low energy electron diffraction (LEED). The surface layer assumes hexagonal packing that induces bucking (the 5x1 unit cell is indicated by a red box). The second layer retains its bulk-terminated square unit cell indicated by a light blue box. (B) Ethylidyne-chemisorption–induced restructuring of Rh (111). The red arrows indicate the expansion of metal atoms around the adsorption sites and the bulking up of metal atoms in the second layer underneath the adsorption sites.

Fig. 3.

The activities of ammonia synthesis over different Fe crystal faces (Right) and the structures of corresponding crystal faces (Left). It was suggested that the surface atoms with high coordination number (C₇ and C₈) are the active sites for ammonia synthesis.

Fig. 4.

Chemical environment effects on surface segregation of the Rh/Pd nanoparticles detected by AP-XPS. In the experiment, the partial pressure of NO or CO is ≈100 mtorr.

Fig. 5.

STM images of Pt(557) in ultrahigh vacuum (A) and under 1 torr of CO (B). (Scale bars: 5 nm.) (C) An enlarged view of B showing the roughly triangular shape of the nanoclusters formed at 1 torr. (D) Coverage of CO on Pt(557) under different pressures as determined by AM-XPS measurements. (E) The relatively stable triangular-shaped nanoclusters predicated by DFT calculations, which provides an explanation to the formation of triangular nanoclusters roughly observed in the STM image shown in C. (Reproduced from ref. 142)

Fig. 6.

(A) Pyrrole hydrogenation. The major products are the aromatic molecule, pyrrolidine, and the ring-opening product, n-butylamine. (B) The SFG spectra of the Pt(111) surface during the pyrrole hydrogenation reaction at 298 K and 363 K. (C) The SFG spectrum of the Pt(100) surface during the pyrrole hydrogenation at 298 K. Pyrrole (3 torr) and 30 torr of hydrogen are used in these studies. Note that the C–H aromatic peak at 3,105 cm⁻¹ (the red color dash line) shows up on the Pt(111) surface at 298 K, and that it is missing on the Pt(111) surface at high temperature (363 K) or on the Pt(100) surface at 298 K.