Nitrate anion reduction in aqueous perchloric acid as an electrochemical probe of Pt{1 1 0}-(1 × 1) terrace sites



Attard, Gary A, Souza-Garcia, Janaina, Martínez-Hincapié, Ricardo and Feliu, Juan M
(2019) Nitrate anion reduction in aqueous perchloric acid as an electrochemical probe of Pt{1 1 0}-(1 × 1) terrace sites. Journal of Catalysis, 378. pp. 238-247.

[img] Text
Manuscript corrected_Ricardo-revision highlighted.docx - Author Accepted Manuscript

Download (115kB)
[img] Text
Figures_Final_RevisadoRicardofina.docx - Author Accepted Manuscript

Download (1MB)

Abstract

The electrochemical reduction of nitrate anions in aqueous 0.1 M perchloric acid has been studied using Pt(S)-[n{1 1 0} × {1 1 1}] and Pt(S)-[n{1 1 0} × {1 0 0}] single crystal electrodes. It is demonstrated that the presence of Pt{1 1 0} adsorption sites is associated with a single, broad nitrate reduction peak centred at 0.18 V (RHE). Moreover, depending on the cooling environment used after flame-annealing (CO, H2, Ar, air, nitrogen), the surface concentration of such sites varies which in turn regulates the nitrate reduction current density achievable for a given stepped Pt{h k l} electrode. The origin of this phenomenon is the propensity of the clean Pt{1 1 0} basal plane (and vicinal surfaces containing this plane) to reconstruct towards a stable (1 × 2) phase with strong CO chemisorption favouring formation of larger Pt{1 1 0}-(1 × 1) domains. In contrast, argon/air-cooling appears to promote the development of a largely (1 × 2) reconstructed surface which is much less active for nitrate reduction since the surface density of Pt{1 1 0}-(1 × 1) terrace sites is significantly diminished. Interestingly, hydrogen-cooling affords nitrate reduction activity intermediate between these two extremes. We suggest that under this particular preparation condition, a partially deconstructed (1 × 1) phase forms containing the “excess” 50% of surface atoms (originating from the (1 × 2) phase) sitting proud of the surface in the form of small (1 × 1) islands, together with residual (1 × 2) missing row regions. Hence, after hydrogen cooling, the nominal Pt{1 1 0} surface plane is speculated to exhibit a wider distribution of smaller terrace widths than found with CO cooling together with residual areas of (1 × 2). The weaker chemisorption of hydrogen apparently limits the size of the Pt{1 1 0}-(1 × 1) domains achievable and consequently, nitrate reduction activity is diminished. Based on these findings, it is proposed that nitrate reduction may be used as a quantitative electrochemical probe of Pt{1 1 0}-(1 × 1) sites at Pt nanoparticles in an analogous fashion to the method of ammonia electrooxidation presently used to quantify the surface abundance of Pt{1 0 0} sites.

Item Type: Article
Uncontrolled Keywords: 7 Affordable and Clean Energy
Depositing User: Symplectic Admin
Date Deposited: 01 Oct 2019 13:13
Last Modified: 17 Mar 2024 05:41
DOI: 10.1016/j.jcat.2019.09.002
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3056545