Nickel Cobalt Oxide Research Articles

3D-stacked electrospun iron-doped nickel cobalt oxide nanofibers as integrated electrodes for anion exchange membrane water electrolysis

The commercialization of anion-exchange membrane water electrolysis (AEMWE) requires the development of highly active, stable, and cheap anode catalysts for the oxygen evolution reaction (OER). In this study, we proposed electrospun iron-doped NiCo2O4 (NCO) nanofibers on nickel foam (NF) and evaluated the performances of the resulting samples (FeX-NCO/NF; X = iron loading in NCO (0, 5, 10, and 15 at %)) as unitized anodes for the OER. Among the fabricated electrodes, Fe10-NCO/NF exhibited the lowest overpotential of 352 mV at a current density of 50 mA cm−2 in a half-cell test owing to its improved intrinsic activity. In an AEMWE single-cell test, Fe10-NCO/NF as anode showed high current density (932 mA cm-2 at 1.8 V) and long-term stability for 150 h The improved AEMWE performance of Fe10-NCO/NF was attributed to efficient mass transport enabled by superhydrophilic three-dimensional porous structure featuring stacked nanofibers.

Role of synthetic process parameters of nano-sized cobalt/nickel oxide in controlling their structural characteristics and electrochemical energy performance as supercapacitor electrodes

The synthesis of nano-sized bimetallic Cobalt/Nickel oxides (Ni1.5Co1.5O4) with a 1:1 Co/Ni atomic ratio has been achieved using a surfactant-free co-precipitation/hydrothermal process. The growth mechanism of Cobalt/Nickel oxides Ni1.5Co1.5O4 is elucidated by tuning the synthesis process parameters, including co-precipitation pH and hydrothermal time. The formation of Cobalt/Nickel oxides Ni1.5Co1.5O4 oxide began with the nucleation of cobalt nickel hydroxide nanoplates through the co-precipitation process, followed by dissolution-recrystallization, stacked hexagonal nano-flakes, and a flower-like microstructure. The electrochemical performances of the oxides were evaluated, with the largest surface area observed at pH 9 being the main factor for the best super-capacitive performance. As hydrothermal time increased, the structural directing growth forward, resulted in the formation of a nano-flower structure with a larger surface area. The as-prepared cobalt nickel oxide exhibited a maximum specific capacitance value of 525.5 F g-1 at a current density of 1 A g-1 and energy and power densities of 88.2 WhKg-1 and 606 WKg-1, respectively.

Palladium-Functionalized Nanostructured Nickel-Cobalt Oxide as Alternative Catalyst for Hydrogen Sensing Using Pellistors.

To meet today's requirements, new active catalysts with reduced noble metal content are needed for hydrogen sensing. A palladium-functionalized nanostructured Ni0.5Co2.5O4 catalyst with a total Pd content of 4.2 wt% was synthesized by coprecipitation to obtain catalysts with an advantageous sheet-like morphology and surface defects. Due to the synthesis method and the reducible nature of Ni0.5Co2.5O4 enabling strong metal-metal oxide interactions, the palladium was highly distributed over the metal oxide surface, as determined using scanning transmission electron microscopy and energy-dispersive X-ray investigations. The catalyst tested in planar pellistor sensors showed high sensitivity to hydrogen in the concentration range below the lower flammability limit (LFL). At 400 °C and in dry air, a sensor response of 109 mV/10,000 ppm hydrogen (25% of LFL) was achieved. The sensor signal was 4.6-times higher than the signal of pristine Ni0.5Co2.5O4 (24.6 mV/10,000 ppm). Under humid conditions, the sensor responses were reduced by ~10% for Pd-functionalized Ni0.5Co2.5O4 and by ~27% for Ni0.5Co2.5O4. The different cross-sensitivities of both catalysts to water are attributed to different activation mechanisms of hydrogen. The combination of high sensor sensitivity to hydrogen and high signal stability over time, as well as low cross-sensitivity to humidity, make the catalyst promising for further development steps.

Water oxidation through electrocatalytic process using cobalt and nickel complexes of thiazole Schiff-base ligands

Ni(OAc)2.4H2O and CoCl2.6H2O reacted with thiazole ligands, HL and HL' (where HL= (E)-2-(((4-phenylthiazol-2-yl)imino)methyl)phenol and HL'= (Z)-2-(2-benzylidenehydrazinyl)-4-phenylthiazole, in ethanol to create new mononuclear Co(II) and Ni(II) complexes, CoL2, NiL2, CoL'2, and NiL'2 (1-4). X-ray diffraction analysis, spectroscopic, and electrochemical methods were used to study the complexes. A carbon paste electrode that had been modified by complexes 1-4 was used as the working electrode in a three-electrode setup to test the complexes' ability in water oxidation reaction at pH 13. The linear sweep voltammetry (LSV) curves showed that complexes 3 and 2 have much greater activity and only require the overpotential of 570 and 690 mV ʋs. RHE at a current density of 10 mA/cm2 with Tafel slopes of 86.92 and 94.19 mVdec−1 respectively in an alkaline solution. In addition, the amperometry tests exhibited brilliant stability for water oxidation by CPE-complex 3 and CPE-complex 2 under electrochemical conditions at pH 13. Although X-ray diffraction patterns did not display a crystalline structure, the scanning electron microscopy images displayed that cobalt oxide and nickel oxide in an alkaline condition are proper catalysts for water oxidation reaction on the surface of the modified electrode.

Non-enzymatic detection of versatile anti-oxidant in diverse media using 3D spinel nickel cobalt oxide with 2D tungsten carbide nanohybrid heterostructure electrocatalyst

Diphenylamine (DPA), an organic amine derivative compound widely used in agriculture and polymer industries as an anti-scaling and anti-oxidising agent. The excessive and prolonged usage of DPA in agricultural products would result in the accumulation of it. The poor degradation ability and associated health hazards marked it as a “contaminant of emerging concern”. Since DPA is not completely banned in many countries, measuring the trace levels of DPA is essential to ensure the safety of the ecosystem. Therefore, the electrochemical sensing method was applied for the precise detection of an infinitesimal concentration of this component. In this work, we have prepared a spinel nickel cobalt oxide with a tungsten carbide (NCO/WC) electrocatalyst-based electrochemical sensor for the accurate detection of DPA. The structural, and morphological details were examined with Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analyses. The electrochemical properties were evaluated with impedance and voltammetric measurements. Various voltammetric techniques were utilized to assess the efficiency of NCO/WC towards DPA. Significantly, our sensor displayed a low detection (0.001 µM), and low quantification (0.0048 µM) limits, good linear range (0.01 to 147 µM), optimal sensitivity (1.716 µA µM−1 cm−2), remarkable selectivity, appreciable repeatability, reproducibility, and stability performance outcomes. Then, the sensor was employed to monitor the DPA in various matrices like agricultural, environmental, and human samples and conquered astonishing results. These findings suggest that our NCO/WC-based electrochemical sensor is a promising platform for the enhanced detection of DPA.

A facile route derived solar selective nickel-cobalt oxide thin films via spraying process

Abstract This work focuses on understanding the role of annealing temperature on the solar selective performance of nickel-cobalt oxide thin films successfully sprayed onto Al substrates using the spray pyrolysis technique. The synthesized nickel-cobalt oxide thin films (~ 725± 20 nm thick) were post annealed at (400, 500 and 600) °C. The XRD and FESEM outcomes appeared high crystalline quality with crystal grains in the range of (27 – 52) nm and improved surface morphology for the sprayed thin films. The optical properties reflect solar absorptance ~ (85.2 %) and the thermal emittance ~ (4.45 %). The hardness and the Young’s modulus were (19.1 GPa) and (104 GPa) respectively. The aforementioned results are for the film annealed at 600 °C. The prepared and post annealed nickel-cobalt oxide thin films show band gap energies in the range of (1.15 – 1.38) eV. The nickel-cobalt oxide thin films also possess excellent thermal stability at higher temperature which makes them interesting candidate for solar absorbing and thermal collector applications.

P-type nickel cobalt oxide synthetized by chemical bath deposition to applications on thin film transistors

This work studies nickel-cobalt oxide (NiCo2O4) thin films synthesized via chemical bath deposition for potential application as p-type active layers in electronic devices. X-ray photoemission electron spectroscopy (XPS) confirms the synthesis of a ternary compound with a stoichiometry of Ni1.04Co1.96O4. The thin film sample exhibiting the closest stoichiometry to the ternary compound has a thickness of approximately 50 nm. Scanning Electron Microscopy (SEM) micrographs indicate an increase in surface porous size corresponding to higher nickel concentrations in the ternary compound. All synthesized NiCo2O4 thin films demonstrate p-type behavior. The lowest resistivity film had a majority carrier concentration of 1×1020 1/cm3, a mobility value of 0.1 cm2/V·s, and a resistivity of 0.1 Ω cm. X-ray diffraction (XRD) studies reveal that the thin films have a type of spinel cubic structure for the phase NiCo2O4. Characteristic spinel bands are observed in the UV–Vis transmittance spectra, and the energy bandgaps of the Ni1.04Co1.96O4 film are estimated to be approximately 3.41 and 2.19 eV using the Tauc method. The thin film with the lowest resistivity was used as an active layer to fabricate a thin-film transistor, displaying typical output curves of a p-channel transistor.

Synthesis of LiCo1-XNiXO2 nanomaterial by hydrothermal method as cathode for lithium ion battery

The compounds of LiCoO2 (LCO) and LiCo1-xNixO2 (LCNO), with (x=0,0.25,0.5,0.75,1) were synthesized as cathode active material for lithium–ion batteries using hydrothermal technique in this study. Structure and morphology characterization were conducted for all prepared samples. The crystalline results indicate that both LCO and LCNO possess a rhombohedral structure, while the morphology results show irregular shapes. Electrochemical tests were carried out for LiCoO2 and LiCo0.25 Ni0.75O2 samples only. From the electrochemical measurements, the LiCo0.25 Ni0.75O2 demonstrate higher charge and discharge capacities compared to the LiCoO2 electrode, findings which are consistent with the electrochemical impedance spectroscopy (EIS) results. The X-ray diffraction (XRD) results of both the prepared Lithium Cobalt Oxide (LCO) and Lithium Cobalt Nickel Oxide (LCNO) samples reveal characteristic peaks at specific angles (2θ) indicating crystallographic planes. For LCO, peaks were observed at 18.96°, 37.40°, 38.35°, 39.07°, 45.29°, 49.45°, and 59.62° corresponding to crystallographic planes (003), (101), (006), (012), (104), (015), and (107) respectively. These peaks confirm the formation of a rhombohedral LiCoO2 nanostructure with space group (R-3m no.166), consistent with standard data (JCPDS 00-016-0427). The EDX spectra of the synthesized Lithium Cobalt Oxide (LCO) and Lithium Cobalt Nickel Oxide (LCNO) were analyzed. The results showed the presence of oxygen (O), cobalt (Co), and nickel (Ni) elements. However, the peak corresponding to lithium (Li) was not visible due to its low activation energy. Finally, the synthesis and characterization of LiCoO2 (LCO) and LiCo1-xNixO2 (LCNO) compounds were conducted, with electrochemical tests indicating superior performance of LiCo0.25 Ni0.75O2 over LiCoO2

Unraveling the Role of the Stoichiometry of Atomic Layer Deposited Nickel Cobalt Oxides on the Oxygen Evolution Reaction.

Nickel cobalt oxides (NCOs) are promising, non-precious oxygen evolution reaction (OER) electrocatalysts. However, the stoichiometry-dependent electrochemical behavior makes it crucial to understand the structure-OER relationship. In this work, NCO thin film model systems are prepared using atomic layer deposition. In-depth film characterization shows the phase transition from Ni-rich rock-salt films to Co-rich spinel films. Electrochemical analysis in 1m KOH reveals a synergistic effect between Co and Ni with optimal performance for the 30 at.% Co film after 500 CV cycles. Electrochemical activation correlates with film composition, specifically increasing activation is observed for more Ni-rich films as its bulk transitions to the active (oxy)hydroxide phase. In parallel to this transition, the electrochemical surface area (ECSA) increases up to a factor 8. Using an original approach, the changes in ECSA are decoupled from intrinsic OER activity, leading to the conclusion that 70 at.% Co spinel phase NCO films are intrinsically the most active. The studies point to a chemical composition dependent OER mechanism: Co-rich spinel films show instantly high activities, while the more sustainable Ni-rich rock-salt films require extended activation to increase the ECSA and OER performance. The results highlight the added value of working with model systems to disclose structure-performance mechanisms.

Constructing an Interlaced Catalytic Surface via Fluorine-Doped Bimetallic Oxides for Oxygen Electrode Processes in Li-O2 Batteries.

Lithium-oxygen (Li-O2) batteries, renowned for their high theoretical energy density, have garnered significant interest as prime candidates for future electric device development. However, their actual capacity is often unsatisfactory due to the passivation of active sites by solid-phase discharge products. Optimizing the growth and storage of these products is a crucial step in advancing Li-O2 batteries. Here, a fluorine-doped bimetallic cobalt-nickel oxide (CoNiO2- xFx/CC) with an interlaced catalytic surface (ICS) and a corncob-like structure is proposed as an oxygen electrode. Unlike conventional oxide electrodes with a "single adsorption catalytic mechanism," the ICS of CoNiO2- xFx/CC offers a "competitive adsorption catalytic mechanism," where oxygen sites facilitate oxygen conversion while fluorine sites contribute to the growth of Li2O2. This results in a change in Li2O2 morphology from a surface film to toroidal particles, effectively preventingthe burial of active sites. Additionally, the unique open architecture aids in the capture and release of oxygen and the formation of well-contacted Li2O2/electrode interfaces, which benefits the complete decomposition of Li2O2 products. Consequently, the Li-O2 battery with a CoNiO2- xFx/CC cathode demonstrates a high specific capacity of up to 30923 mAh g-1 and a lifespan exceeding 580 cycles, surpassing most reported metal oxide-based cathodes.

Facile fabrication of nickel-cobalt oxide for efficient oxygen evolution reaction from ammonia leaching solution of spent lithium-ion batteries

Ammonia leaching has been gained considerable attention for its ability to selectively extract nickel and cobalt from spent ternary cathode material. Despite its efficacy, the subsequent recovery of ammonia leachate remains challenging. Herein, a short-process and sustainable method for the synthesis of nickel-cobalt oxide via ammonia evaporation of ammonia leachate and heat treatment of the resultant precursor has been proposed. The ammonia evaporation process, conducted at an evaporation temperature of 130 °C with hydrazine hydrate as a reducing agent, facilitated the precipitation of ∼95% Ni and ∼99% Co as a precursor. Subsequently, the effect of precursor roasting temperature on electrode material synthesis was systematically studied. The precursor was roasted at 300 °C to successfully synthesize nickel-cobalt oxide. Physical and electrochemical characterizations revealed that the nickel-cobalt oxide possesses a significant specific surface area of 161.150 m2/g, and exhibits excellent oxygen evolution reaction performance, evidenced by an overpotential of 350.7 mV at 10 mA/cm2 and a Tafel slope of 159.8 mV/dec. Overall, the proposed method not only promotes the recycling and utilization of ammonia reagents and mother liquor, but also introduces an innovative approach for the synthesis of nickel-cobalt oxide as an electrode material.

Rapid fabrication of binder free nickel cobalt oxide electrodes with dendritic nanostructure for electrochemical energy storage applications

A rapid and facile technique to synthesize nickel cobalt oxide electrodes by photothermal treatment of mixed organometallic precursor solution is reported. Using short and intense pulses of light from a xenon flash lamp, spray coated films are converted into porous nickel cobalt oxide electrodes with dendritic nanostructure. The electrode films fabricated in a few seconds show excellent energy storage properties as supercapacitor electrodes. Specific capacitance of up to 116 Fg−1 and capacitance retention of up to 75 % were observed in samples with low mass loading. Analysis of the cyclic voltammetry (CV) curves shows that capacitance is the dominating charge storage mechanism in these films. To study the effect of varying the mass loading in electrodes, double and triple layered electrodes were also studied. In films with high mass loading, the specific capacitance of the films decreased but areal capacitance continued to increase. A high areal capacitance of up to 243 mFcm−2 is observed in films with high mass loading. CV curve analysis of high mass loading electrodes further shows that in films with higher mass loading, the charge storage mechanism is a mix of capacitance and diffusion processes. The contribution of diffusion increased with increase in the mass loading of the electrodes. This study sheds light into the mechanism of charge storage in electrodes prepared by large-scale-amenable single step process of photonic curing which could be utilized to fabricate electrodes in industrial scale.

Electrochromic Durability and Color Variation of Thickness-Controlled Nanosheet-Structured Nickel–Cobalt Oxide Thin Films

Electrochromic Durability and Color Variation of Thickness-Controlled Nanosheet-Structured Nickel–Cobalt Oxide Thin Films

Phosphorus-doped nickel cobalt oxide (NiCo2O4) wrapped in 3D hierarchical hollow N-doped carbon nanoflowers as highly efficient bifunctional electrocatalysts for overall water splitting

Properly design and fabricate capable electrocatalysts with 3D hierarchical hollow framework to realize cost-effective and efficacious overall water splitting (OWS) are particularly meaningful for the large-scale arrangement of pivotal energy technology. In this study, P-doped NiCo2O4 nanoparticles encapsulated in N-doped carbon hierarchical hollow nanoflowers (P-NiCo2O4@NCHHNFs) were constructed using the hydrothermal-pyrolysis-phosphorization approach. This fascinating architecture can not merely serve as a conductive pathway for electron transfer, but at the same time effectively inhibited the aggregation and corrosion of the NiCo2O4 nanoparticles. Additionally, the P doping not only regulates electronic structure configuration to boost the intrinsic activity of the catalyst, but also enhance electrochemical surface areas to reveal more accessible active sites. Attributing to these characteristics, the as-prepared P-NiCo2O4@NCHHNFs exhibit preeminent electrocatalytic performance with low overpotentials of 283 mV and 162 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) (at 10 mA cm−2), respectively. Specifically, by using the P-NiCo2O4@NCHHNFs as bifunctional catalysts, a low potential of 1.56 V (at 10 mA cm−2) is sufficient to drive overall water splitting with splendid durability. This study proposed an innovative strategy for the conceiving and fabricating high-performance catalysts via heteroatom-doping.

Hierarchically Structured Graphene Aerogel Supported Nickel-Cobalt Oxide Nanowires as an Efficient Electrocatalyst for Oxygen Evolution Reaction.

The rational design of a heterostructure electrocatalyst is an attractive strategy to produce hydrogen energy by electrochemical water splitting. Herein, we have constructed hierarchically structured architectures by immobilizing nickel-cobalt oxide nanowires on/beneath the surface of reduced graphene aerogels (NiCoO2/rGAs) through solvent-thermal and activation treatments. The morphological structure of NiCoO2/rGAs was characterized by microscopic analysis, and the porous structure not only accelerates the electrolyte ion diffusion but also prevents the agglomeration of NiCoO2 nanowires, which is favorable to expose the large surface area and active sites. As further confirmed by the spectroscopic analysis, the tuned surface chemical state can boost the catalytic active sites to show the improved oxygen evolution reaction performance in alkaline electrolytes. Due to the synergistic effect of morphology and composition effect, NiCoO2/rGAs show the overpotential of 258 mV at the current density of 10 mA cm-2. Meanwhile, the small values of the Tafel slope and charge transfer resistance imply that NiCoO2/rGAs own fast kinetic behavior during the OER test. The overlap of CV curves at the initial and 1001st cycles and almost no change in current density after the chronoamperometric (CA) test for 10 h confirm that NiCoO2/rGAs own exceptional catalytic stability in a 1 M KOH electrolyte. This work provides a promising way to fabricate the hierarchically structured nanomaterials as efficient electrocatalysts for hydrogen production.

Facile synthesis of cobalt-nickel oxide nanocomposites for trifunctional application towards antioxidant, anticancer and electrochemical performance

Transition metallic mixed oxides have received a lot of curiosity due to their exceptional electrochemical performance and incredibly low cost for hybrid supercapacitors. Herein, we report a facile synthetic approach of cobalt nickel oxide (CNC) composites from Carica papaya leaf extract. The synthesized mixed oxide composite was analyzed by various spectroscopic techniques (IR, UV–Vis, Powder XRD, SEM-EDAX, TEM and XPS). The electrochemical behavior of CNC was investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) method in 2 M KOH solution. The composites exhibit specific capacitance of 289.28 F g−1 at 1 A g−1 demonstrating improved charge storage. The electrode retains 81 % of its specific capacitance from the initial value after repeated charge–discharge processes for 2000 cycles. In addition to the electrochemical studies, biological activities such as anti-oxidant and anti-cancer activities of the CNC were examined. The radical scavenging activity of CNC was assessed with different radicals such as DPPH•, ABTS+., NO–, OH•, O2– and the acquired results showed that the composites possessed substantial activity. Anticancer activity of CNC was studied against HepG2 and MM2 cancer cells and the CNC possessed significant activity with the IC50 value of 45.8 and 38.3 µg/ml respectively compared with the standard drug cisplatin. Further apoptogenic nature of the CNC was confirmed with DAPI staining assay.

NiCo2O4 Nanowires Immobilized on Nitrogen-Doped Ti3C2Tx for High-Performance Wearable Magnesium-Air Batteries.

Flexible magnesium (Mg)-air batteries provide an ideal platform for developing efficient energy-storage devices toward wearable electronics and bio-integrated power sources. However, high-capacity bio-adaptable Mg-air batteries still face the challenges in low discharge potential and inefficient oxygen electrodes, with poor kinetics property toward oxygen reduction reaction (ORR). Herein, spinel nickel cobalt oxides (NiCo2O4) nanowires immobilized on nitrogen-doped Ti3C2Tx (NiCo2O4/N-Ti3C2Tx) are reported via surface chemical-bonded effect as oxygen electrodes, wherein surface-doped pyridinic-N-C and Co-pyridinic-N moieties accounted for efficient ORR owing to increased interlayer spacing and changed surrounding environment around Co metals in NiCo2O4. Importantly, in polyethylene glycol (PVA)-NaCl neutral gel electrolytes, the NiCo2O4/N-Ti3C2Tx-assembled quasi-solid wearable Mg-air batteries delivered high open-circuit potential of 1.5V, good flexibility under various bent angles, high power density of 9.8mW cm-2, and stable discharge duration to 12h without obvious voltage drop at 5mA cm-2, which can power a blue flexible light-emitting diode (LED) array and red smart rollable wearable device. The present study stimulates studies to investigate Mg-air batteries involving human-body adaptable neutral electrolytes, which will facilitate the application of Mg-air batteries in portable, flexible, and wearable power sources for electronic devices.

Coupling electrocatalytic CO2 reduction with glucose oxidation for concurrent production of formate with high efficiency

Electrocatalytic reduction of CO2 (CO2ER) coupled with the oxygen evolution reaction (OER) is an energy-intensive process that generates low-value oxygen, limiting its industrial application. To overcome this limitation, here we report a membrane electrode assembly (MEA) system that combines CO2ER with glucose electrooxidation (GEOR) to simultaneously produce formate using bismuth subcarbonate and carbon nanotube hybrid (BOC-CNT) and nickel cobalt oxide decorated on carbon fiber paper (NCO-CFP) as the cathode and anode catalysts, respectively. The BOC-CNT catalyst showed excellent electrocatalytic performance for CO2ER to formate, affording a high FEHCOO- of 97.9 % with current density of 360 mA cm−2 at −0.77 V vs. RHE (-580 mV overpotential), and the NCO-CFP catalyst achieved GEOR at 0.99 V (vs. RHE) with FEHCOO- >98 %. The coupled CO2ER//GEOR MEA exhibits a low onset cell voltage of 1.20 V and reaches ultrahigh apparent Faraday efficiency of formate (>190 %) in a wide range from 1.8 to 2.4 V, achieving ∼ 33.3 % energy savings compared to CO2ER//OER with a high formate yield of 0.92 mol g-1h−1 at 100 mA cm−2. Besides, all generated formate can be collected from the electrolyte on the anode side due to the spontaneous migration of formate under electric field, thus reducing cross-contamination from CO2 and alkaline electrolytes. In addition, the coupled CO2ER//GEOR system exhibited good electrocatalytic stability for at least 32 h. This strategy provides an innovative and promising approach for the co-electrolytic transformation of biomass derivatives and CO2 to formate.

Unravelling the catalytic activity of copper cobalt oxide - nickel cobalt oxide composites for efficient counter electrode performance in DSSCs

Undoubtedly, the counter electrode (CE) plays a dominant role on the power conversion efficiency (PCE) of Dye Sensitized Solar Cells (DSSCs), as it regenerates the redox couple and responsible for the continuous activity of the device. Yet, the conventional platinum CE is highly expensive and needs to be replaced with equivalent material to achieve low-cost devices. Aiming this, fabricated DSSCs with Cubic - Copper Cobalt Oxide (C-CCO), Cubic - Nickel Cobalt Oxide (C-NCO) and the composite of C-CCO and C-NCO [i.e C-(CCO/NCO)] as CEs. The Cyclic Voltammetry analysis shows that the minimum peak to peak separation (Epp) value of 0.34 V was obtained for C-(CCO/NCO), indicating that the composite shows excellent catalytic activity. Further, the charge diffusion coefficient and charge transfer resistance of C-(CCO/NCO) composites significantly favour the DSSCs performance. As our main result, we obtained a maximum PCE of 4.56% for C-(CCO/NCO), whereas the efficiency of C-CCO and C-NCO are 3.66% and 3.71%, respectively. The fabricated DSSCs show relatively better performance than contemporary spinel-oxide based DSSCs. The synergetic effect of the composite materials is analysed extensively to understand the improved performance.

Crystalline Structure and Optical Properties of Cobalt Nickel Oxide Thin Films Deposited with a Pulsed Hollow-Cathode Discharge in an Ar+O2 Gas Mixture

Cobalt nickel oxide films are deposited on Si(111) or fluorine-doped tin-oxide-coated (FTO) glass substrates employing a pulsed hollow-cathode discharge. The hollow cathode is operated with argon gas flowing through the nozzle and with O2 gas admitted to the vacuum chamber. Three different cathode compositions (Co20Ni80, Co50Ni50, and Co80Ni20) are investigated. Deposited and annealed thin films are characterized by X-ray diffraction, infrared (Raman) spectroscopy, and ellipsometry. As-deposited films consist of a single mixed cobalt nickel oxide phase. Upon annealing at 600 °C, the mixed cobalt nickel oxide phase separates into two cystalline sub-phases which consist of cubic NiO and cubic Co3O4. Annealed films are investigated by spectroscopic ellipsometry and the optical bandgaps are determined.