The Role of Steps on Silver Nanoparticles in Electrocatalytic Oxygen Reduction

Abstract

Hydrogen fuel cell technology is an essential component of a green economy. However, it is limited in practicality and affordability by the oxygen reduction reaction (ORR). Nanoscale silver particles have been proposed as a cost-effective solution to this problem. However, previous computational studies focused on clean and flat surfaces. High-index surfaces can be used to model active steps presented in nanoparticles. Here, we used the stable stepped Ag(322) surface as a model to understand the ORR performance of steps on Ag nanoparticles. Our density functional theory (DFT) results demonstrate a small dissociation energy barrier for O2 molecules on the Ag(322) surface, which can be ascribed to the existence of low-coordination number surface atoms. Consequently, the adsorption of OOH* led to the associative pathway becoming ineffective. Alternatively, the unusual dissociative mechanism is energetically favored on Ag(322) for ORR. Our findings reveal the importance of the coordination numbers of active sites for catalytic performance, which can further guide electrocatalysts’ design.

Sulfidation Impacts on the Hydrophobicity of Stepped Iron Surfaces

“…In our previous research, we discovered that stepped surfaces can significantly influence water adsorption and dissociation processes. [27][28][29] Specifically, we used Fe(210) and Fe(211) as model systems and found that stepped surfaces are more reactive and more susceptible to corrosion by water than flat Fe(110). [27,28] However, our current understanding of S-covered stepped nZVI surfaces are limited.…”

Effects of Oxygen Adsorption on the Optical Properties of Ag Nanoparticles

“…In part because of the catalytic applications of Ag-based materials in epoxidation reactions, the reactivity of Ag surfaces and nanostructures toward O 2 has been extensively addressed both experimentally − and in computational studies. − The first relevant study in this regard can be traced back to that of Rovida et al in 1972, where adsorption of oxygen over Ag(111) was described. , When scaling down from metal surfaces to metal nanoparticles, size effects and effects related to the presence of more undercoordinated metal sites emerge, making the dissociation of O 2 more facile. , However, it is challenging to determine which are the stable equilibrium structures of oxidized Ag systems; the structure and chemical state of Ag surface oxides have been actively investigated and discussed, ,, but for Ag NPs, little is known.…”

“… 32 , 47 When scaling down from metal surfaces to metal nanoparticles, size effects and effects related to the presence of more undercoordinated metal sites emerge, making the dissociation of O 2 more facile. 48 , 49 However, it is challenging to determine which are the stable equilibrium structures of oxidized Ag systems; the structure and chemical state of Ag surface oxides have been actively investigated and discussed, 29 , 31 , 32 but for Ag NPs, little is known.…”