Research Project: Karbondioksitin Elektrokimyasal İndirgenmesi İçin Ayarlanabilir Seçiciliğe Sahip Bakır Tabanlı Katalızörlerin İleri Sentez ve Karakt erizasyon Yöntemleri İle Tasarlanması
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Contributors
Funders
ID
TB.00450
Authors
Zarenezhad, Hamaneh
Researcher
Publications
Enhancement in CO selectivity by modification of ZnO with CuxO for electrochemical reduction of CO2
(Wiley-V C H Verlag Gmbh, 2023) Balkan, Timuçin; Kaya, Sarp; Tafazoli, Saeede; Yusufoğlu, Muhammed; 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 electrochemical reduction reaction of carbon dioxide (CO2RR) has garnered significant attention due to its potential for the formation of carbon monoxide, which has industrial relevance. Herein, an oxide-derived Cu-Zn electrocatalyst with an optimized CuxO layer that shows high selectivity toward CO with a faradic efficiency of 75% at a low overpotential (-0.8 V vs reversible hydrogen electrode) is reported. Various structural characterizations and activity tests are conducted to understand the origin of this improvement depending on the CuxO amount. Electrochemical surface area and electrochemical impedance spectroscopy measurements suggest that the addition of CuxO increases double-layer capacitance and decreases charge transfer resistance. Scanning electron microscopy images indicate that the electrodes undergo a severe reconstruction process, which is further confirmed by X-ray diffraction that shows the formation of CuZn4 alloy during the reduction reaction. Furthermore, X-ray photoelectron spectroscopy depth profile analysis shows that after CO2RR at -0.8 V, the Cu/Zn ratio is higher than that after -1.2 V, which suggests that applied potential plays a significant role in the reconstruction process and hence the difference in selectivity. The presence of copper in the surface layer has a significant impact on the improvement of selectivity toward CO.
In-situ surface enhanced Raman spectroscopy investigations on surface transformations of oxide derived copper electrodes during CO2RR
(Academic Press Inc Elsevier Science, 2023) Balkan, Timuçin; Kaya, Sarp; Tafazoli, Saeede; Yusufoğlu, Muhammed; 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
We investigated the catalytic activity and C2 selectivity in electrochemical carbon dioxide reduction reac-tion (CO2RR) on two distinguished electrodeposited Cu oxides with distinct morphologies and structures. The electrode with a compact structure exhibited two times higher faradaic efficiencies of C2 products (40%). Through utilizing electrochemical surface-enhanced Raman spectroscopy (SERS), it was realized that the formation of a metastable phase (malachite) on electrode surfaces by consumption of HCO3- could cause a shift in local pH. The analysis of SERS indicated a strong correlation between the presence of the malachite phase and strongly-adsorbed CO on electrode surfaces, preventing dimerization and fur-ther reduction. This malachite phase terminating the surface can hinder the charge exchange and inter-fere with further reductions in C2 products.
ALD-engineered CuxO overlayers transform ZnO nanorods for selective production of CO in electrochemical CO2 reduction
(American Chemical Society, 2024) Balkan, Timuçin; Jahangiri, Hadi; Kaya, Sarp; Tafazoli, Saeede; Yağcı, Mustafa Barış; Yusufoğlu, Muhammed; Department of Chemistry; Graduate School of Sciences and Engineering; KUTEM (Koç University Tüpraş Energy Center); KUYTAM (Koç University Surface Science and Technology Center); Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
The electrochemical CO2 reduction reaction (CO2RR) holds tremendous promise as a strategy for lowering atmospheric CO2 levels and creating new clean energy sources. The conversion of CO2RR to CO, in particular, has garnered significant scientific interest due to its industrial feasibility. Within this context, the CuZn-based electrocatalyst presents an attractive alternative to conventional CO-selective electrocatalysts, which are often costly and scarce. Nevertheless, the wide-range utilization of CuZn electrocatalysts requires a more comprehensive understanding of their performance and characteristics. In this study, we synthesized ZnO nanorods through electrodeposition and subsequently coated them with CuxO overlayers prepared by atomic layer deposition (ALD). CuxO significantly enhanced CO selectivity, and 88% CO selectivity at a relatively low potential of -0.8 V was obtained on an optimized CuxO overlayer thickness (CuxO-250/ZnO). The addition of CuxO on ZnO was found to dramatically increase the electrochemical surface area (ESCA), lower the charge-transfer resistance (R-ct), and introduce new active sites in the epsilon-CuZn4 phase. Furthermore, electrochemical Raman spectroscopy results showed that the CuxO-250/ALD electrode developed a ZnO layer on the surface during the CO2RR, while the bare ZnO electrode showed no evidence of ZnO during the reaction. These results suggest that the addition of CuxO by ALD played a crucial role in stabilizing ZnO on the surface. The initial amount of CuxO was shown to further affect the redeposition of the ZnO layer and hence affect the final composition of the surface. We attribute the improvement in CO selectivity to the introduction of both epsilon-CuZn4 and ZnO that developed during the CO2RR. Overall, our study provides new insights into the dynamic behavior and surface composition of CuZn electrocatalysts during CO2RR.
Alkali metal cations at work: Enhancing CO2 electroreduction to CO on ZnO nanorods
(Elsevier, 2024) Balkan, Timuçin; Kaya, Sarp; Şekercioğlu, Azra; Tafazoli, Saeede; Yusufoğlu, Muhammed; Department of Chemistry; KUTEM (Koç University Tüpraş Energy Center); Graduate School of Sciences and Engineering; Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
Oxide-derived zinc, an abundant and cost-effective electrode material alternative to gold and silver, has exhibited high activity for the electroreduction of CO2 to CO (CO2RR). However, the impact of cations on the CO2RR activity remains unexplored. In this study, we investigated the effect of three alkali metal cations (Cs+, K+, and Li+) on the CO2RR over a ZnO nanorod electrode, using a rotating ring disk electrode (RRDE) technique. Cyclic voltammetry of the Pt ring in the RRDE tip reveals a consistent trend in the buffering capacity of these cations (Cs+ > K+ > Li+), as evidenced by the availability of OH- ions for CO electrooxidation and hydrogen oxidation reactions (HOR). Cs+ showed a pronounced effect on the activity of the CO2RR to CO since it can regulate OH- concentration and maintain the local pH. This study addresses the ongoing debate concerning the effects of cations;interfacial electric field and buffering capacity;and elucidates the relationship among electrolyte/cation, local pH dynamics, and the CO2RR activity towards CO over the active oxide-derived Zn electrodes, all derived from the fast and facile RRDE technique.
