Özlem Budak

Bio: Özlem Budak is an academic researcher from Marmara University. The author has contributed to research in topics: Graphene & Materials science. The author has co-authored 4 publications.

Simultaneous electrochemical deposition of nickel cobalt oxide-reduced graphene oxide composites for high performance asymmetric supercapacitors

Abstract: In this work, a one-step electrodeposition approach was applied for nanosheets fabrication of binder free nickel cobalt oxide (NCO) and NCO-reduced graphene oxide (NCO-rGO) composites on the nickel-foam substrate by repetitive cyclic voltammetry (rCV). The NCO-rGO hybrids were firstly fabricated on Ni foam surface with the reduction of GO and electrodeposition of NCO simultaneously. Interaction of NCO particles with rGO sheets increased the conductivity of the composite and consequently facilitated the electron transfer rate. Electrochemical measurements proved that specific capacitance and cyclic performance of as-prepared materials were improved with the synergistic effect of rGO in the hybrid structure. The optimized NCO-rGO electrode exhibited a specific capacitance of 1916.5 F g−1 at 1 A g−1 with superior stability of 95.6% at a high current density of 10 A g−1 even after 3000 cycles. To explore its practical applications, an asymmetric supercapacitor (ASC) based on NCO-rGO as a positive electrode and rGO as a negative electrode was constructed, which exhibited a prominent specific energy of 45.22 Wh kg−1 at 400 W kg−1. As a result, NCO-rGO hybrid structure as the functional electrode material for the supercapacitors with remarkable electrochemical performance were obtained, thanks to the increased conductivity and decreased mass by removing binders.

Zinc(ii) phthalocyanine–viologen dyads: synthesis, electrochemistry, spectroelectrochemistry, electrodeposition, and electrochromism

Abstract: Electrochromic properties have been enriched by combining the anodic colorant zinc phthalocyanine and cathodic colorant viologen moieties into a dyad system via a flexible chain.

Recent advances in solution assisted synthesis of transition metal chalcogenides for photo-electrocatalytic hydrogen evolution.

Abstract: Hydrogen evolution from water splitting is considered to be an important renewable clean energy source and alternative to fossil fuels for future energy sustainability. Photocatalytic and electrocatalytic water splitting is considered to be an effective method for the sustainable production of clean energy, H2. This perspective especially emphasizes research advances in the solution-assisted synthesis of transition metal chalcogenides for both photo and electrocatalytic hydrogen evolution applications. Transition metal chalcogenides (CdS, MoS2, WS2, TiS2, TaS2, ReS2, MoSe2, and WSe2) have received intensified research interest over the past two decades on account of their unique properties and great potential across a wide range of applications. The photocatalytic activity of transition metal chalcogenides can further be improved by elemental doping, heterojunction formation with noble metals (Au, Pt, etc.), non-chalcogenides (MoS2, In2S3, NiS1-X), morphological tuning, through various solution-assisted synthesis processes, including liquid-phase exfoliation, heat-up, hot-injection methods, hydrothermal/solvothermal routes and template-mediated synthesis processes. In this review we will discuss recent developments in transition metal chalcogenides (TMCs), the role of TMCs for hydrogen production and various strategies for surface functionalization to increase their activity, different synthesis methods, and prospects of TMCs for hydrogen evolution. We have included a brief discussion on the effect of surface hydrogen binding energy and Gibbs free energy change for HER in electrocatalytic hydrogen evolution.

Electrical and photoelectrical properties of a vacuum-deposited MnClPc/n-Si heterojunction for photodiode application

Abstract: Thin films of MnClPc/n-Si heterojunctions were performed by the thermal evaporating technique. The C–V and G-V characteristics of the diode under the effect of frequency were investigated. It was found that the capacitance and the conductance spectra are significantly affected by AC-signal at the low-frequency range due to the presence of the interfacial states (Nss) and the series resistance (Rs) in the depletion region. The I–V characteristics of MnClPc/n-Si under the dark and illumination in the reverse and forward bias were studied. Under the assumption of thermionic emission theory, the rectification ratio (RR = IF/IR), the shunted and series resistances, and the ideality factor of the diode were calculated. The evaluated height potential barrier (φb) values from the I–V characteristic and by Cheung and Cheung method were 0.84 and 0.57 eV, respectively. Regarding the power-law (I ∼ Vm) relation, the charge transport mechanism is described by the space charge limited current associated with a single trap level. Moreover, the I–V characteristics under the illumination intensity were investigated. Whereas the photosensitivity readings under dark and illumination intensity reveal the probability of using MnClPc/n-Si heterojunctions as a performance photodiode sensor.