In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2020-02, No. 63 ( 2020-11-23), p. 3216-3216
Abstract:
The concentration of CO 2 in the atmosphere continues to increase. As a result, global warming is considered to be progressing due to the greenhouse effect. Therefore, the goal of "achieving a balance between human-made emissions of greenhouse gases and removals by sinks in the second half of this century" is set and decreasing the CO 2 emissions has become an urgent issue. Recently, it was found that the CO 2 electroreduction in an acidic solution on a Pt-based electrode catalyst, such as Pt or PtRu, proceeds at around 0.05 V vs. SHE, which means that CO 2 reduction occur with extremely low overvoltage [1]. Our research group has previously reported that a Pt oxide thin film exhibits a higher CO 2 electroreduction activity than a Pt one, and the factors affecting the superior CO 2 electroreduction activity was considered by Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS) [2,3]. In this study, CO 2 electroreduction activity of Pt and Pt-Cu electrodes were evaluated and its difference was investigated by in-situ SEIRAS. The specimen was a Pt thin film or Pt oxide thin film, which were prepared on a Ti substrate by reactive sputtering. The detailed procedure was described in a previous report. The rotating disk electrode was fabricated from a Ti substrate coated with the Pt thin film or the Pt oxide thin film. It was attached to the electrode rotation system as the working electrode, and the CO 2 electroreduction activity was evaluated. The counter electrode and the reference electrode were a Pt sheet and an Ag/AgCl in 3.30 mol dm -3 KCl, respectively. The electrolytic solution was a 0.1 kmol dm -3 HClO 4 aqueous solution. For in-situ SEIRAS, the electrocatalysts were supported in Au thin film which was prepared by electroless deposition on a semi-cylindrical Si prism. The resolution of the infrared spectrometer was 4.0 cm -1 , and the detector was a liquid nitrogen-cooled MCT detector. The IR spectrum measured at 1.2 V vs. RHE was used as a reference. Fig. 1 shows the cycic voltammograms of the Pt thin film. In Ar-deaerated atmosphere, typical characteristics of Pt was observed. However, the oxidation current was recognized at around 0.6 V vs. SHE in CO 2 -saturated solution. This anodic peak reflects the CO 2 electroreduction activity [2]. Fig. 2 shows the relationship between CO 2 electroreduction activities per active surface area and Cu content of the prepared thin films. The CO 2 electroreduction activities of the Pt-Cu thin films were higher than that of the Pt thin film. Thus, we used SEIRAS to perform in-situ analysis of the surface adsorption species during the electroreduction to investigate the factors involved in the high electroreduction activity of the Pt Cu electrodes. Fig. 3 shows the Relationship between the intensity of adsorbed linear-CO, HCOO -, and methanol during the CO 2 electroreduction reaction on Pt-65.2 at.% Cu/C with time. The potential was maintained at 0.05 V vs. RHE for the CO 2 electroreduction to occur. The peaks of the linear-CO and methanol increase with an increase in time. This indicates the amount of linear-CO and methanol adsorbed on the surface was increasing. On the other hand, for HCOO - , although peaks were observed, the absorbance was obviously lower than that for CO. These behaviors were the same as for Pt [3]. Therefore, the difference of CO 2 electroreduction activity between Pt and Pt-Cu is not related to the intermediate product and adsorption species. Fig. 4 shows the CO coverage of Pt/C and Pt-65.2at.% Cu/C estimated by CO-stripping voltammetry. Although almost all the surface of Pt was covered by CO, about half of the surface of Pt-Cu maintained clean condition. Therefore, we can say that the better CO 2 electroreduction activities of Pt-Cu electrodes are brought by a weak adsorption characteristic of CO. [1] S. Shironita, K. Sato, K. Yoshitake, and M. Umeda, Electrochim. Acta , 206 , 254 (2016). [2] K. Ohkubo, H. Takahashi, and M. Taguchi, J. MMIJ , 135(2) , 8 (2019). [3] K. Ohkubo, H Takahashi, E.P.J. Watters, and M Taguchi, Electrochemistry , 88(3) , 210 (2020). Figure 1
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2020-02633216mtgabs
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2020
detail.hit.zdb_id:
2438749-6
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