The significance of the local structure of cobalt-based catalysts on the photoelectrochemical water oxidation activity of BiVO4. (10th January 2021)

• Record Type: Journal Article
• Authors: Barzgar Vishlaghi, Mahsa; Kahraman, Abdullah; Apaydin, Sinem; Usman, Emre; Aksoy, Dilan; Balkan, Timuçin; Munir, Shamsa; Harfouche, Messaoud; Ogasawara, Hirohito; Kaya, Sarp
• Is Part Of: Electrochimica acta. Volume 366(2021)
• Publication Date: 2021-01-10
• Subjects: Water oxidation kinetics -- BiVO4 -- Cobalt-based catalyst -- Local structure -- Atomic layer deposition; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2020.137467
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Dissimilar cobalt oxide (hydroxide) phases are obtained by atomic layer deposition (ALD). The local environment of cobalt on BiVO4 is critical for its performance. The most active cobalt phase for water oxidation in neutral pH is Co(OH)2 deposited on BiVO4 by ALD. Co(OH)2 boosts the water oxidation photocurrent of BiVO4 by 95% at 0.6 VRHE . Co(OH)2 facilitates the hole transfer from BiVO4 to the electrolyte more than CoO. Abstract: The local structures of the water oxidation catalysts play an important role in reaction kinetics and the performance of the photoanodes. In this study, we deposited cobalt-based catalysts on nanoporous BiVO4 with controlled thicknesses by atomic layer deposition (ALD). Despite the similar oxidation states of cobalt in all depositions, different water oxidation activities in neutral pH conditions were observed. A dramatic photocurrent raise, lowered kinetic overpotential, and smaller charge transfer resistance across the photoanode/electrolyte interface were achieved when a uniform ultrathin Co(OH)2 layer was formed on BiVO4 . Photocurrent density for water oxidation showed a 95% enhancement at 0.6 V vs. RHE when the catalyst was in the form of Co(OH)2, while an 80% increase was obtained for CoO. Ideal coordination of Co(OH)2 on hydroxylated BiVO4 surface assists the charge transfer between the electrolyte and BiVO4 without increasing surface recombination. The results of this study emphasize the importance of controlling the local structure of the catalysts in the performance of the water splitting photoanodes. Graphical abstract: Image, graphical abstract