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.
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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 |
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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 |