Rational Design of Catalytic Surfaces for Fuel Cell Technologies by Selective Molecular Patterning

Abstract

Current green technologies demand for deep and fundamental research. In this sense it has been reported that selective molecular patterning can be employed for the development of highly active electrocatalysts[1,2]. Pt is the most active single-component catalyst for many surface reactions and modifying it with other elements can improve its catalytic performance and stability.Here selective molecular patterning of Pt surfaces with adatoms of Bi and Te at coverages varying from 1/16 ML to 1/4 ML has been studied using DFT to explore changes in the electronic properties of both the adatom and Pt, the sum of which affects catalytic performance of the resulting system.The obtained results indicate that both adatoms are very stable on low-index platinum surfaces at all coverages. The work function of pristine Pt surfaces depends on the exposed plane, and decreases in order (111) > (100) > (110) [4]. In good agreement with experimental data [3] the presence of the adatoms lowers the work function and results in a new trend: (100) > (110) > (111). Further lowering of the model surfaces’ work function with increasing adatoms’ coverage (Table1) also agrees well with the tendencies observed in experimental study of Pt(111) interaction with Bi [3].Table 1. Adatom-Pt(111) WF values. Experimental data for Bi/Pt from ref. [3] is included as well System Coverage Δ WF / eV Experimental value Bi/Pt(111) 0.06 0.73 0.77 0.12 1.26 1.15 0.18 1.65 1.53 0.25 1.96 1.75 Te/Pt(111) 0.06 0.47 — 0.12 0.88 — 0.18 1.22 — 0.24 1.50 — Bi and Te adsorption leads to the charge transfer to the surfaces and the electron density, remaining on the adatoms, gets reorganized to assure the maximal distance from the neighboring Pt atoms, leading to the polarization of the adatom-Pt bond.The adatom-induced changes in the fundamental properties of platinum, such as work function and position of the d-band center, have been observed for both species on all studied surfaces. Even at low 1/16ML coverage Bi and Te not only may block active sites on platinum, but also have a more fundamental impact on its catalytic properties.