Effects of Capping Agents on the Oxygen Reduction Reaction Activity and Shape Stability of Pt Nanocubes. Issue 22 (14th October 2019)

• Record Type: Journal Article
• Authors: Safo, Isaac A.; Dosche, Carsten; Özaslan, Mehtap
• Is Part Of: Chemphyschem. Volume 20:Issue 22(2019)
• Page Start: 3010
• Page End: 3023
• Publication Date: 2019-10-14
• Subjects: oleylamine, oxygen reduction reaction -- polyvinylpyrrolidone -- Pt nanocubes -- shape stability; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201900653
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: We investigated the formation of Pt nanocubes (NCs) and their electrocatalytic oxygen reduction reaction (ORR) properties and structural stability using two different capping agents, namely, polyvinylpyrrolidone (PVP) and oleylamine (OAm). The mono‐dispersity of the obtained Pt NCs and their interactions with PVP and OAm were analyzed by transmission electron microscopy (TEM), energy dispersive X‐ray spectroscopy (EDX), X‐ray photoelectron spectroscopy (XPS), Fourier‐transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The TEM data show a high mono‐dispersity (82 %) and a large mean particle size (9‐10 nm) for the Pt NCs obtained by the oleylamine‐assisted method compared to those prepared via the PVP‐assisted procedure (68 %, 6–7 nm). FTIR, XPS, and TGA data show that PVP and OAm still remain at the Pt surface, despite washing. Interestingly, the OAm‐capped Pt NCs show significantly higher electrochemically active surface area (ECSA) and ORR activity than the PVP‐capped ones. An accelerated stress protocol, however, reveals that the OAm‐capped NCs possess a poor structural stability during electrochemical cycling. The loss of a defined surface arrangement in the NCs is connected with a transformation into a near‐spherical particle shape. In contrast, the PVP‐capped NCs mainly retain their particle shape due to their strong capping behavior. In addition, we have developed a degradation model for NCs as a function of electrochemical parameters such as upper potential and cycle number. Altogether, we provide fundamental insights into the electronic interactions between capping agent and Pt NCs and the role of the adsorption strength of the capping agent in improving the electrochemical ORR performance as well as the structural stability of shape‐controlled nanoparticles. Abstract : Insights into the electronic interactions between capping agents and Pt nanocubes (NCs) for electrochemical oxygen reduction reaction (ORR) performance and structural stability are given. Oleylamin‐capped Pt NCs show higher electrochemically active surface area (ECSA) and ORR activity than PVP‐capped ones. An accelerated stress protocol shows that the oleylamin‐capped NCs possess a poor structural stability, resulting in the transformation into near‐spherical particles. In contrast, the PVP‐capped NCs mainly retain their particle shape due to their strong capping behavior. A degradation model for the NCs as a function of electrochemical parameters is presented.