Research Project: Günes Enerjisini Kullanarak Bütünlesik Su Ayrısması Yoluyla Yesil Hidrojen Üretimi Için Aktif Fotoelektrotların Gelistirilmesi
Loading...
Contributors
Funders
ID
TB.00648
Authors
Kaya, Sarp
Faculty Member
Publications
Hybrid cufe-cofe Prussian blue catalysts on BIVO4 for enhanced charge separation and injection for photoelectrochemical water oxidation
(American Chemical Society (ACS), 2022) Barzgarvishlaghi, Mahsa; Kaya, Sarp; Usman, Emre; Vishlaghi, Mahsa Barzgar; Akbari, Sina Sadigh; Karadas, Ferdi; Department of Chemistry; Graduate School of Sciences and Engineering; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
The utilization of cocatalysts on the photoelectrode surface is a feasible strategy to achieve a high photocurrent density in the photoelectrochemical water oxidation process. The catalysts can enhance the activity by improving the reaction kinetics, retarding charge carrier recombination, or accumulating charge carriers. In this work, we have utilized a CuFe-CoFe Prussian blue (PB) catalyst layer on the BiVO4 photoanode surface to enhance its water oxidation activity. The hybrid catalyst, in which the semiprecious cobalt ions are partially substituted with earth-abundant copper ions, exhibits 56% higher photocurrent density than the CoFe PB-modified BiVO4. We show that photogenerated hole accumulation is present in the CuFe PB layer, which results in higher charge extraction from the BiVO4 surface. The CoFe PB layer on top of the CuFe one facilitates the charge transfer due to its catalytic activity toward the oxygen evolution reaction (OER).
Cation vacancy-mediated ultrafast hole transport in CuBi2O4 photocathodes
(John Wiley and Sons, 2024) Ardalı, Emir; Jahangiri, Hadi; Kaya, Sarp; Sennaroğlu, Alphan; Solati, Navid; Yahsi, Ugur; Tav, Cumali; Department of Physics; Department of Chemistry; KUYTAM (Koç University Surface Science and Technology Center); Graduate School of Sciences and Engineering; KUTEM (Koç University Tüpraş Energy Center); Department of Electrical and Electronics Engineering; Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center; College of Engineering
As a promising photocathode candidate, tetragonal CuBi2O4 (CBO) has been studied extensively in recent years. As an intrinsically p-type material, its acceptor sites originate from the cation vacancies, which are also a potential cause of hindered hole utilization in photocathodes. In this study, the ultrafast transport dynamics of the valence band hole states in CBO photocathodes were investigated by varying their atomic composition and manipulating the p-type character. As a comprehensive ultrafast optical transient absorption spectroscopy (TAS) investigation of compositionally manipulated CBO that combines both ex situ and in situ TAS experiments with photoelectrochemical (PEC) performance tests, the study reveals the polaron formation tendencies of the valence band (VB) holes at cationic vacancy sites. Therefore, it draws a complete picture of the ultrafast hole transport dynamics and provides valuable insights into the hindrance of the photocurrent generated in CBO.
Accelerating water oxidation on BiVO4 photoanodes via surface modification with Co dopants
(Royal Soc Chemistry, 2023) Barzgarvishlaghi, Mahsa; Kahraman, Abdullah; Kaya, Sarp; Sennaroğlu, Alphan; Usman, Emre; Osterbacka, Nicklas; Erdem, Emre; Wiktor, Julia; Department of Physics; Department of Chemistry; KUTEM (Koç University Tüpraş Energy Center); KUYTAM (Koç University Surface Science and Technology Center); Graduate School of Sciences and Engineering; Yes; College of Sciences; Research Center; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Despite the vast investigations on improving the photoelectrochemical performance of BiVO4 for water splitting, charge recombination in the near-surface region remains a challenge. In this study, we showed that the diffusion of Co2+ ions into the BiVO4 subsurface boosted the water oxidation activity and charge injection efficiency remarkably. The increase in the concentration of oxygen vacancies upon the incorporation of cobalt ions was shown by electron paramagnetic resonance (EPR) spectroscopy and confirmed by density functional theory (DFT) calculations. DFT calculations revealed that vanadium sites in the subsurface region were the most favorable sites for substitution with cobalt ions. Charge localization at surface oxygen vacancies was found less favorable in the presence of cobalt in the subsurface layer, eliminating surface recombination. This resulted in 4.25 times larger charge injection efficiency and 6.2 times higher photocurrent density at the potential of & SIM;0.6 V, as compared to pristine BiVO4. This enhancement was significantly larger as compared to CoOx-loaded BiVO4, indicating that the suppressed recombination at the surface and improved charge transfer kinetics obtained solely by CoOx deposition are not sufficient for enhanced activity of BiVO4. A longer charge carrier lifetime obtained upon cobalt incorporation was observed by transient absorption spectroscopy and verified the reduced rate of recombination.
