Research Project: Grafenin Hidrojenerasyon ve Nitrojenerasyon kapasitesinin Geliştirilmesi
Loading...
Contributors
Funders
ID
TB.00173
Authors
Kaya, Sarp
Faculty Member
Publications
Elementary steps of the oxygen reduction reaction on nitrogen-doped graphene revealed by Raman spectroelectrochemistry
(Wiley, 2025) Kaya, Sarp; Solati, Navid; Department of Chemistry; Graduate School of Sciences and Engineering; KUHyTech (Koç University Hydrogen Technologies Center); Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
Nitrogen-doped graphene (N-doped graphene) is a promising material for electrochemical applications, particularly as a catalyst in the oxygen reduction reaction (ORR). Despite numerous studies, the detailed mechanism of ORR on N-doped graphene remains unresolved. This study utilizes spectroelectrochemical Raman (SEC-Raman) spectroscopy to investigate the elementary steps of the ORR on graphene doped with pyridinic and graphitic nitrogen configurations. A comprehensive Raman spectral analysis reveals the evolution of adsorbed species and active sites during the reaction, suggesting an unconventional pathway involving outer-sphere electron transfer and unique adsorption dynamics. These insights clarify the interplay between nitrogen configurations and catalytic performance, offering a deeper understanding of the structure-activity relationship in N-doped graphene. The findings pave the way for improved design and optimization of metal-free ORR electrocatalysts.
Charge transfer controlled hydrogenation of graphene on an electronically modified Pt(111) surface
(Pergamon-Elsevier Science, 2020) Kahraman, Abdullah; Kaya, Sarp; Panahi, Mohammad; Solati, Navid; Balkan, Timuçin; Pis, Igor; Bondino, Federica; 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 interfaces of graphene and hydrogenated graphene with 3d atom embedded Pt(111) [Pt-3d-Pt(111), 3d: Fe, Co] substrates have comparatively been investigated utilizing X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and temperature-programmed XPS (TPXPS) and desorption (TPD). 3d atoms in the subsurface layer of Pt(111) change the electronic properties of graphene via modifying its p-doping level. Hydrogenation makes graphene pinned to the Pt(111) and Pt-3d-Pt(111) substrates and induces surface segregation of 3d atoms from the subsurface layer into the interface of HGr and Pt-3d-Pt(111). Such a mechanism changes the desorption energetics of hydrogen significantly.
Weakening the strength of CO binding on subsurface alloyed Pt(111)
(Elsevier, 2019) Kaya, Sarp; Panahi, Mohammad; Solati, Navid; Gürlek, Sezen; Ogasawara, Hirohito; 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 interaction of CO with Pt/3d/Pt(111) subsurface alloys (3d: Ni, Co, Fe) was investigated by combination of vibrational spectroscopy and temperature programmed desorption. The binding strength of CO is significantly reduced on Pt/Fe/Pt(111) and Pt/Co/Pt(111) and is sorted in the following order: Pt >Ni > Co approximate to Fe. Our analysis shows that the 3d admetal is stable in the subsurface region and CO is linearly bonded to the atop sites of the Pt(111) surface. At high CO coverage, compressed structures are obtained. At low CO coverage, the desorption activation energy of CO (similar to 143 kJ/mol for Pt(111)) drops to 124 kJ/mol for Pt/Ni/Pt(111), and goes further down to 111 and 110 kJ/mol for Pt/Co/Pt(111) and Pt/Fe/Pt(111), respectively. The enhancement in the surface activity is attributed to the modified backdonation to the antibonding states of adsorbed CO due to the downshifted 5d-band center of Pt upon embedding 3d metals in the subsurface region.
Easy hydrogenation and dehydrogenation of a hybrid graphene and hexagonal boron nitride monolayer on platinum
(Institute of Physics (IOP) Publishing, 2021) Kahraman, Abdullah; Kaya, Sarp; Panahi, Mohammad; Pis, Igor; Nappini, Silvia; Magnano, Elena; Bondino, Federica; 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
Understanding the fundamental steps of adsorption and controlled release of hydrogen in two-dimensional (2D) materials is of relevance for applications in nanoelectronics requiring tuning the physical properties or functionalization of the material, hydrogen storage and environmental sensors. Most applications demand that hydrogen adsorption and desorption can be controlled at room temperature. Here we report an element-specific study on the hydrogenation and dehydrogenation, in a low coverage regime, of a quasi-free standing 2D heterostructure (h-BNG) in the form of coexisting lateral domains of isostructural hexagonal boron nitride (h-BN) and graphene (Gr) on Pt(111). At very low hydrogen coverage a selective and partial hydrogenation of the Gr domains is observed in h-BNG. At the same time no changes are detected in the h-BN domains, indicating a preferential hydrogenation of Gr rather than h-BN domains. At higher coverage, hydrogenation of both Gr and h-BN domains is detected. A thermally facile hydrogen release from h-BN domains near room temperature is observed. Furthermore, the hybrid h-BNG 2D heterostructure enables also a much easier H-2 thermal release from Gr domains when compared with a full Gr monolayer grown on the same Pt(111) substrate. These results suggest that the presence of coexisting hydrogenated h-BN domains could destabilize C-H bonds in Gr.
Modifying hydrogen binding strength of graphene
(Elsevier, 2019) Kaya, Sarp; Panahi, Mohammad; Solati, Navid; N/A; 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 effect of the substrate on the binding strength of hydrogen on single layer graphene grown on Pt(111) surfaces has been investigated via determining its desorption activation energy. We showed that subsurface alloys on Pt(111) can dramatical modify the C-H bond strength in hydrogenated graphene. Various 3d metals, vanadium, iron, cobalt, and nickel were deposited in the subsurface layer to modify the chemical and electronical properties of the substrate. Analysis of the temperature programmed desorption data shows that subsurface alloys reduce the hydrogen desorption activation energy by weakening C-H bond energy in graphene, down to 57 kJ/mol in the case of Pt/Co/Pt(111) as compared to similar to 111 kJ/mol obtained from hydrogenated graphene grown on a bare Pt(111).
