Enhancing electrocatalytic activity in metallic thin films through surface segregation of carbon

Kousar, Ayesha; Quliyeva, Ulviyya; Pande, Ishan; Sainio, Jani; Julin, Jaakko; Sajavaara, Timo; Karttunen, Antti J.; Laurila, Tomi

doi:10.1039/d3cp04316a

Cited by 2 publications

(5 citation statements)

References 51 publications

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“…As this is a diffusion-driven process, it will require time. As observed in our recent paper, Cr 2 O 3 serves as an effective diffusion barrier for carbon, which is not formed in the case of CrNi-5 due to the above-discussed delay. Consequently, carbon can infiltrate deeper into the layers, resulting in a more evenly distributed carbon concentration profile and a reduced tendency for surface segregation.…”

Section: Discussionsupporting

confidence: 58%

“…Therefore, in this study, we deposited Ni as a catalyst layer on top of commonly used Ti and Cr adhesion layers on silicon substrates to form CrNi (80 nm of Cr and 20 nm of Ni) and TiNi (20 nm of Ti and 20 nm of Ni) substrates commonly used for growing carbon nanofibers. , These metal layers were annealed at 600 °C for 5 (TiNi-5, CrNi-5) and 20 min (TiNi-20, CrNi-20) in a PECVD chamber (excluding the use of reactive gases and plasma) to mimic the typical ambient conditions during CNF growth. , We then studied the microstructural changes of these commonly used interfacial metal stacks as a result of annealing and attempted to correlate these with their electrochemical activity toward DA and AA. We found that the presence of Ni drastically modifies the microstructure, surface chemistry, and electrochemical activities of Ti and Cr adhesion layers in comparison to that observed in the previous study . Our findings provide a thorough examination of how the Ni catalyst layer alters the microstructure of the Ti and Cr adhesion layers, consequently affecting surface chemistry and electrochemical characteristics.…”

Section: Introductionsupporting

confidence: 50%

“…In contrast, the CrNi-5 surfaces lacked the presence of carbides or sp 2 -bonded carbon. This implies that in the case of TiNi, sp 2 carbon segregation to the surface occurs earlier compared to CrNi, which is completely opposite to that observed in plain systems Cr and Ti without Ni . Despite titanium’s known high carbon and oxygen solubility, the presence of nickel reduces their solubility, leading to carbon segregation on the surface.…”

Section: Discussionmentioning

confidence: 84%

“…Conversely, chromium appears to dissolve both carbon and oxygen because the presence of nickel significantly delays the formation of surface carbon layers. In a previous study, we demonstrated that annealing increases the solubility of carbon and oxygen in the titanium layer . Notably, nickel fundamentally alters titanium’s behavior, promoting the formation of carbides, silicides, and segregated carbon layers, indicating reduced carbon solubility, attributed to nickel acting as a known β-Ti stabilizer (see Ti–Ni binary phase diagram).…”

Section: Discussionmentioning

confidence: 85%

“…We have shown in the previous report that (i) in the case of Cr/Si thin layers, surface segregation of carbon induces electrochemical activity. This is a result of (a) the formation of Cr 2 O 3 , which inhibits the diffusion of carbon uniformly throughout the films and (b) the low solubility of graphite to Cr 2 O 3 .…”

Section: Introductionmentioning

confidence: 88%

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Ni Drastically Modifies the Microstructure and Electrochemistry of Thin Ti and Cr Layers

Kousar,

Quliyeva,

Pande

et al. 2024

J. Phys. Chem. C

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There is a significant lack of literature addressing changes in the microstructure of different interfacial metal layer combinations employed in fabricating electrochemical sensors based on carbon nanomaterials. This research gap extends to analyzing their influence on the electrochemical performance, which, in turn, impacts the understanding of the properties of materials incorporating these layers. In this study, microstructural variations and electrochemical activity of chromium and titanium adhesion layers, in combination with nickel catalyst layers (designated as TiNi and CrNi), on silicon wafers were analyzed post annealing. Interestingly, during a brief annealing period of 5 min, TiNi developed a surface layer comprising graphitic carbon, alongside the formation of TiO 2 , TiC, and NiSi, and exhibited electrochemical activity toward both dopamine (DA) and ascorbic acid (AA). Conversely, CrNi annealed for 5 min did not show the presence of such a carbon layer and displayed no discernible electrochemical activity toward the target molecules. Only after an extended annealing time of 20 min, signs of a carbon layer appear on CrNi, displaying a moderate electrochemical activity toward DA and AA. The formation of a carbon layer on CrNi is delayed due to the presence of Ni near the surface, which disrupts the local equilibrium. Consequently, the formation of the Cr 2 O 3 barrier layer is delayed, which in turn permits carbon diffusion into the underlying Cr layer. Conversely, Ni stabilizes the β-Ti form and markedly decreases the solubility of carbon and oxygen within the TiNi system. By providing a comprehensive analysis of microstructural changes and their impact on the surface chemistry and electrochemical responses of commonly used interfacial metal layers, this paper offers invaluable insights in selecting suitable adhesion and catalyst layer combinations for carbon nanomaterial fabrication.

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Section: Discussionsupporting

confidence: 58%