Reduced CO sub(2) on a polycrystalline Rh electrode in acid solution: Electrochemical and in situ IR reflectance spectroscopic studies

• Published in: Electrochimica acta 1998-01, Vol.44 (8-9), p.1369-1378
• Main Authors: Arevalo, M C, Gomis-Bas, C, Hahn, F
• Format: Article
• Language: English
• ISSN: 0013-4686

Comparative studies of the electrochemical behaviour of CO sub(2) on a polycrystalline Rh electrode in acid solution by electrochemical and spectroelectrochemical measurements are reported. Aqueous solutions of H sub(2)SO sub(4), HClO sub(4) and CF sub(3)SO sub(3)H have been used. In order to produce r-CO sub(2) adsorbates, different adsorption potentials (E sub(ad)) in the H-atom electrosorption potential range and in the hydrogen evolution region (HER) were chosen. The values of charge density of adsorbate oxidation (q sub(ox)) depend on E sub(ad), on the solution composition and on the adsorption time (t sub(ad)). At constant E sub(ad) and t sub(ad), q sub(ox) increases in the following order: H sub(2)SO sub(4) < CF sub(3)SO sub(3)H < HClO sub(4) in agreement with the adsorption strength of anions. The same sequence was observed in the oxidation peak potentials of the adsorbates produced. To analyzed the influence of r-CO sub(2) adsorbates in the HER, polarization curves have also been recorded. Studies have been carried out with in situ infrared reflectance spectroscopy. Three techniques were employed: SNIFTIRS, SPAIRS and potential steps. Several main IR bands are observed and associated with CO sub(2) and CO (CO sub(B) bridge-bonded and CO sub(L) linearly bonded). Other bands are also observed between 1000-1800 cm super(-1) which show the existence of other adsorbed species as well as around 1000-1100 and 2800-3000 cm super(-1). This observation leads to the supposition that another more reduced species is formed from CO sub(2).