A phosphotungstic acid-supported single metal atom is a potential electrocatalyst for the nitrogen reduction reaction with high activity and high selectivity.

The deposition of a two-dimensional (2D) atomic nanosheet on a metal surface has been considered as a new route for tuning the molecule-metal interaction and surface reactivity in terms of the confinement effect. In this work, we use first-principles calculations to systematically explore a novel nanospace constructed by placing a 2D graphitic carbon nitride (g-CN) nanosheet over a Pt(111) surface. The confined catalytic activity in this nanospace is investigated using CO oxidation as a model reaction. With the inherent triangular pores in the g-CN overlayer being taken advantage of, molecules such as CO and O can diffuse to adsorb on the Pt(111) surface underneath the g-CN overlayer. Moreover, the mechanism of intercalation is also elucidated, and the results reveal that the energy barrier depends mainly on the properties of the molecule and the channel. Importantly, the molecule-catalyst interaction can be tuned by the g-CN overlayer, considerably reducing the adsorption energy of CO on Pt(111) and leading to enhanced reactivity in CO oxidation. This work will provide important insight for constructing a promising nanoreactor in which the following is observed: The molecule intercalation is facile; the molecule-metal interaction is efficiently tuned; the metal-catalyzed reaction is promoted.

CO oxidation on phosphomolybdic acid (H3PMo12O40, PMA) supported single-metal atom (M = Pt, Au, Co, Cu, Fe, Ir, Ni, Os, Pd, Ag, Rh, and Ru) (M-PMA) catalysts is studied by density-functional-theory (DFT) calculations. Adsorption of CO and O2 on M-PMA is investigated. Based on electronic structure analysis, O2 is activated by the single-metal-atom active center. The Langmuir-Hinshelwood mechanism is systematically explored for CO oxidation on M-PMA, and it is found that M-PMAs have high reactivity toward CO oxidation. The Mars-van Krevelen mechanism is also investigated and it is shown to be less likely to be responsible. Our DFT findings will provide useful insight for designing stable, highly active heteropolyacid-supported single-metal-atom catalysts.