Linear Sweep Voltammetry Measurements Research Articles

A new concept of ternary aqueous electrolytes based on lithium 4,5-dicyanoimidazolate hydrates

A new concept of aqueous electrolytes based on heterocyclic anions (hydrated anionic triplet electrolyte, HATE) has been presented. Structural studies showed that dimeric lithium 4,5-dicyanoimidazolate (LiTDI) dihydrate molecules, in the presence of acetonitrile, form an ionic system preserved in high concentrations and solid states. X-ray diffraction measurements show that electroneutral dihydrate units can coordinate additional lithium cations acting as charge carriers. The crystalline ionic phase was characterized using spectroscopic, thermal, and electrochemical methods and was used to prepare model electrolytes based on LiTDI hydrates. Linear sweep voltammetry and impedance spectroscopy measurements show, in this system, the depletion of water activity, high conductivity, and reversible cycling of full cells comprising examined electrolytes. We will prove that a concentrated triplet solution acts similarly to the anhydrous electrolyte; regardless of the concentration, it reaches high ionic conductivity values (12–16 mS/cm at room temperature) and is electrochemically stable.

Electrodeposition of Ru on Nanoscale Trench Patterns

Ru deposition in advanced technology nodes can improve performance by providing low resistance in nanoscale features. In this study, we reported the electrochemical reactions of Ru3+ on an Ru surface using multi-cyclic voltammetry (CV) and behavior of additives during Ru electrodeposition using linear sweep voltammetry (LSV) and potentiostatic measurements. Disodium 3,3’-dithiobis(1-propanesulfonate) (SPS), polyvinylpyrrolidone (PVP), and a bromide ion (Br−) were added for bottom-up filling. We investigated the suppression behavior of PVP. The current density and the onset potential of suppressor breakdown were affected by the suppressor concentration. PVP interacted synergistically with Br− and showed additional suppression. PVP formed a suppressing layer with Br− after formation of a bromide layer. SPS could reduce roughness during electrodeposition of Ru. Based on these results, nano-trenches were filled with Ru using the optimized additive condition.

Co-Ni co-sputter deposited bimetallic thin film catalysts for alkaline hydrogen and oxygen evolution reactions

Co-Ni bi-metallic thin films with different stoichiometries have been deposited by magnetron co-sputtering technique on Ni foam (NF), Si and carbon paper substrates. The structural and morphological characterisations of these films have been done by X-ray diffraction, X-ray absorption spectroscopy and Field Emission Scanning Electron Microscope measurements. The performances of these films for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been evaluated through electrochemical measurements like Linear Sweep Voltammetry, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy measurements. Operando X ray absorption near edge spectroscopy measurements have also been carried out during HER and OER to decipher the redox reaction mechanisms. It has been observed that the HER and OER performance of all the Co Ni bi-metallic thin films on NF are found to be better than that of bare NF. The CoNi sample with composition of 58.7 % Co and 41.3 % Ni shows the best catalytic activity and stability towards HER and OER reactions. Though the HER activity is not the best but is comparable to many results reported in the literature, however the catalyst shows excellent OER activity with overpotential of 214 mV for 10 mA/cm2 current density. This is much better than that of the OER benchmark catalyst RuO2 and most of those reported in the literature. The OER is kinetically slower than HER and requires more overpotential, hence a significant improvement in the catalytic OER activity will definitely enhance the overall water splitting activity and hydrogen production efficiency. Thus the Co-Ni bi-metallic catalyst prepared by an easily scalable and highly reproducible magnetron co-sputtering technique has significant potential to emerge out as a technologically viable water splitting catalyst.

Eco-Sustainable Aluminum-Air Batteries

Aluminum-air batteries are energy conversion devices considered to be promising alternative to lithium-ion batteries due to their high theoretical energy density as well as the easy availability and recyclability of the anode material. The use of neutral water-based electrolytes and raw materials of natural or synthetic but biodegradable origin in the battery components, mainly electrolytes and cathodes, adds further advantages of safety, affordable costs and eco-friendliness. In this work, the electrochemical performance of aluminum-air batteries assembled with gel polymer electrolytes, made of natural polysaccharides and saline aqueous solutions, was investigated and discussed, through comparing the results obtained using cathodes based on platinum catalyst with respect to those based on a cheaper wood-derived activated carbon. Three-electrodes discharge measurements, rate performance tests, polarization and power density curves, and linear sweep voltammetry measurements were used to critically compare different cathodic materials used in combination with neutral electrolytes. The results show that the best electrochemical performances were obtained for aluminum-air cells assembled with wooden biomass-derived air cathodes.

Corrosion behavior of high- and low-chromium steel grinding balls in chloride solution

The corrosion behaviour of three types of alloys (two low-alloy carbon steel and one stainless iron with ~15 wt.% Cr), in a solution which simulates seawater (3% NaCl solution, pH 8.1) was tested. Tested samples are used to make steel (iron) balls applied in mils for grinding copper and other ore. The corrosion tests were performed using three electrochemical methods, at room temperature in the presence of atmospheric oxygen. The linear polarization resistance (LPR) method, electrochemical impedance spectroscopy (EIS) method, and linear sweep voltammetry (LSV) method were applied. Based on measurements by LPR and EIS methods (as non-destructive methods), the value of polarization resistance (Rp) was determined and the general corrosion rate (vcorr) of the examined samples was calculated. The obtained values of the general corrosion rate can be used to calculate the service life of steel (iron) balls under exploitation conditions (seawater). The appearance of the surface after linear sweep voltammetry (LSV) measurement showed the presence of localized corrosion (pits were formed) of the tested samples, especially stainless iron, and the LSV method is not suitable for the determination of the general corrosion rate of tested samples in seawater. This form of corrosion occurs at high anodic polarizations, during performing LSV measurements.

Boosting nitrate electroreduction reactivity with a 3D Cu-Pd bimetallic flow-through electrode

NO3− pollution in water and wastewater is a pressing global environmental issue, leading to the deterioration of water quality and an increased risk to human health. Herein, we present a three-dimensional (3D) flow-through electrode composed of electrodeposited Cu-Pd bimetallic catalysts on a nickel foam. The Cu-Pd bimetallic particles exhibited cluster-like shapes on the surface of the nickel foam. This electrode design enhanced the electrochemical activity of the NF/Cu63Pd37 electrode for NO3− reduction, as evidenced by linear sweep voltammetry (LSV) measurements. By tailoring the Cu-Pd ratio (Cu:Pd 0.63:0.37), the NF/Cu63Pd37 electrode showed the highest reactivity of NO3− reduction and selectivity (43.1 %) toward N2. Importantly, the NF/Cu63Pd37 electrode not only achieved over 99 % NO3− removal but also exhibited a higher kinetic rate constant of 1.44 h−1 in the flow-through mode. In contrast, in the flow-by mode, NO3− removal was 67.5 % with a lower reaction rate constant of 0.30 h−1. Furthermore, the NF/Cu63Pd37 electrode exhibited a reduced energy consumption (EEO) of 6.86 kWh m−3 order−1 in the flow-through mode, contrasting with 13.66 kWh m−3 order−1 in the flow-by mode. Moreover, the results also demonstrated successful NO3− remediation across various initial pH values (pH 3, 6, 9, and 11) and NO3− concentrations (100, 200, and 300 mg L−1). The results of this study highlight that the 3D Cu-Pd bimetallic flow-through electrode, with its high reactivity in reducing NO3−, marks a significant advancement in efficiently treating nitrate-contaminated water.

Exploring the Potential of α-MnO<sub>2</sub>/ Carbon Nanotubes for Improved Oxygen Reduction Reaction Performance at the Cathode of Alkaline Fuel Cells

In the field of fuel cell technology, the development of cost-effective catalysts is crucial for the commercialization of Alkaline Membrane Fuel Cells (AMFCs). Platinum (Pt) has traditionally been employed as the catalyst in AMFCs, but its high cost poses a major barrier to widespread adoption. In this study, a new catalyst material was developed by incorporating Manganese Dioxide (α-MnO2) into Carbon Nanotubes (CNTs) using hydrothermal synthesis techniques. The synthesized catalyst was characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), and its electrocatalytic activity was evaluated through Linear Sweep Voltammetry (LSV) and CV through Rotating Disc Electrode (RDE) experiments. The results showed that the α-MnO2-CNT composite displayed strong durability in the alkaline environment and high electrocatalytic activity for oxygen reduction reaction (ORR). The LSV measurements revealed a current density of -4.1 mA/cm2 and an overpotential of -0.3V relative to Standard Calomel Electrode (SCE) in a 0.1M KOH electrolyte. Additionally, the α-MnO2-CNT composite displayed high methanol tolerance and long-term stability compared to commercial Pt/C catalysts. This study demonstrates that the use of α-MnO2-CNT as a cost-effective alternative to Pt has the potential to facilitate the commercialization of AMFC technology.

Lithium Dendrite Propagation in Ta-Doped Li7La3Zr2O12 (LLZTO): Comparison of Reactively Sintered Pyrochlore-to-Garnet vs LLZTO by Solid-State Reaction and Conventional Sintering.

Ta-doped Li7La3Zr2O12 (LLZTO) garnet is a promising Li-ion-conducting ceramic electrolyte for solid-state batteries. However, it is still challenging to use LLZTO in Li metal batteries operating at high current densities because of the tendency for Li metal to nucleate and propagate along the grain boundaries. In this study, we carry out a detailed investigation to elucidate the effect of microstructure and grain size on the electrochemical properties and short circuit behavior in LLZTO. Pellets were prepared using reactive sintering from pyrochlore precursors (a method called pyrochlore-to-garnet, P2G) and compared with LLZTO synthesized using solid-state reaction (SSR) followed by conventional pressureless sintering. Both preparation methods were controlled to keep the phase and elemental composition, ionic and electronic conductivity, relative density, and area-specific resistance of the pellets constant. Reflection electron energy loss spectroscopy and X-ray photoelectron spectroscopy confirm that both types of LLZTO have similar band gaps and chemical states. Microstructure analysis shows that the P2G method results in LLZTO with an average grain size of around 3 μm, which is much smaller than the grain sizes (as large as 20 μm) seen in SSR LLZTO. Galvanostatic Li stripping/plating and linear sweep voltammetry measurements show that P2G LLZTO can withstand higher critical current densities (up to 0.4 mA/cm2 in bidirectional cycling and >1 mA/cm2 for unidirectional) than those seen in SSR LLZTO. Post-mortem examination reveals much less Li deposition along the grain boundaries of P2G LLZTO, particularly in the bulk of the pellet, compared to SSR LLZTO after cycling. The improved cycling behavior in P2G LLZTO despite the higher grain boundary area could be from more homogeneous current density at the interfaces and different grain boundary properties arising from the liquid-phase, reactive sintering method. These results suggest that the effect of grain size on Li dendrite propagation in LLZO may be highly dependent on the synthesis and sintering method employed.

Low-Pressure Plasma-Processed NiCo Metal–Organic Framework for Oxygen Evolution Reaction and Its Application in Alkaline Water Electrolysis Module

Ar, Ar/H2 (95:5), and Ar/O2 (95:5) plasmas are used for treating the NiCo metal–organic framework (MOF), and the plasma-processed NiCo MOF is applied for catalyzing the oxygen evolution reaction (OER) in a 1 M KOH electrolyte. Linear sweep voltammetry measurements show that after plasma treatment with Ar/H2 (95:5) and Ar gases, the overpotential reaches 552 and 540 mV, respectively, at a current density of 100 mA/cm2. The increase in the double-layer capacitance further confirms the enhanced oxygen production activity. We test the Ar plasma-treated NiCo MOF as an electrocatalyst at the OER electrode and Ru as an electrocatalyst at the hydrogen evolution reaction (HER) electrode in the alkaline water electrolysis module. The energy efficiency of the electrolyzer with the Ar plasma-processed NiCo-MOF catalyst increases from 54.7% to 62.5% at a current density of 500 mA/cm2 at 25 °C. The alkaline water electrolysis module with the Ar plasma-processed catalyst also exhibits a specific energy consumption of 5.20 kWh/m3 and 4.69 kWh/m3 at 25 °C and 70 °C, respectively. The alkaline water electrolysis module performance parameters such as the hydrogen production rate, specific energy consumption, and energy efficiency are characterized at temperatures between 25 °C and 70 °C. Our experimental results show that the NiCo MOF is an efficient OER electrocatalyst for the alkaline water electrolysis module.

3D TiO2 modified with reduced graphene embed into polyvinyl alcohol: photoanode electrode for oxygen evolution reaction

The photocatalytic hydrogen production from water splitting using solar energy is one of the promising trend research topics within the scope of green energy production. A photoelectrochemical set up consists of photoelectrode materials that directly uses photon energy convers water to hydrogen and oxygen. The photoelectrodes are photoanode and photocathode materials n-type and p-type semiconductor, respectively. In this study, the 3D TiO2 photoanode surface was modified by coating it with reduced graphene (rG) added polyvinyl alcohol (PVA) gel. PVA synthetic polymer with thermal stability, mechanical stability and low cost was preferred to provide distribution of rG material on 3D TiO2 active surfaces. In this context, different amounts of rG (2.5, 5, 10 and 20%, based on polymer weight) impregnated with PVA gel coated on the 3D TiO2 semiconductor surface were investigated. The solar light absorption behaviour and molecular interactions of the different amounts of rG in PVA on 3D TiO2 semiconductor were monitored by UV-vis and Raman spectrometer. A photocatalytic performance of photoelectrodes were conducted by Electrochemical Impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and chronoamperometric measurement under 100 mW cm-2 solar light. Raman spectrum showed dispersion of RG in PVA. EIS measurement showed that the polarization resistance (Rp) increased in 3D TiO2 with only PVA coating, while the addition of rG to PVA caused a decrease in Rp at the semiconductor/electrolyte interface under sunlight. Furthermore, LSV and chronoamperometric measurement concluded that the increased amount of rG added to PVA increased the photoresponse of 3D TiO2 up to the limit rG value.

Polycarbonate-Based Solid-Polymer Electrolytes for Solid-State Sodium Batteries.

Solid-polymer electrolytes comprised of polypropylene carbonate (PPC) and varied sodium bis(fluorosulfonyl)imide (NaFSI) salt concentrations are investigated for implementation as a conductive solid polymer electrolyte into solid-state cathode composites utilizing a sodium-layered oxide active material. The ionic conductivity generally increases with NaFSI salt content, reaching ≈1mScm-1 at 80°C at the highest salt concentration (PPC:NaFSI = 0.5:1). Through an all-in-one slurry casting method, Na2/3Ni1/3Mn2/3O2 cathode composites are fabricated in which the dispersed PPC electrolyte acts as the primary binder. Enabled by a bilayer polymer electrolyte system, cycling performance with the PPC cathode electrolyte is optimized with respect to salt concentration and anode material. The best cyclability is achieved with a moderate salt concentration electrolyte (PPC:NaFSI = 5:1), showcasing an initial capacity of 83mAhg-1 with a remarkable 80% capacity retention after 150 cycles at C/5 rate and 60°C. The superior performance of the lower salt concentration electrolyte is attributed to better electrochemical stability, as confirmed by linear sweep voltammetry and online electrochemical mass spectrometry measurements. These results underscore the potential of carbonate-based polymer electrolytes and the importance of balancing electrolyte conductivity and stability in cell design.

Investigation of NiCoOx catalysts for anion exchange membrane water electrolysis: Performance, durability, and efficiency analysis

Anion exchange membrane (AEM) water electrolysis is a promising method for hydrogen production using inexpensive metal oxide catalysts. This study investigates the catalytic activity and performance of nickel cobalt oxide (NiCoOx) catalysts in AEM water electrolysis for hydrogen production. The catalysts were synthesized with varying ratios of Ni to Co. The NiCoOx catalysts were coated on nickel foam gas diffusion layer (GDL) at the anode. Scanning electron microscopy (SEM) analysis revealed a distinct flaky structure of the NiCoOx catalyst. X-ray diffraction (XRD) studies confirmed the presence of NiCo2O4 spinel crystal structure in the catalysts. Linear sweep voltammetry (LSV) measurements for Oxygen evolution reaction (OER) in three electrode systems showed that NiCoOx (1:3) exhibited the highest catalytic activity, with a current density of 238 mA cm−2 at 1.8 V. Tafel analysis indicated that NiCoOx (1:3) had the lowest Tafel slope, suggesting faster reaction kinetics and lower overpotential for higher current density. Chronoamperometry tests demonstrated the stability of the catalysts at various current densities, and long-term stability testing of NiCoOx (1:3) for 500 h revealed minimal voltage increase during OER, demonstrating its stability in prolonged operation. NiCoOx (1:3) displayed the highest activity among the catalysts at different temperatures, with current densities reaching 1700 mA cm−2 at 2.2 V and 70 °C for single-cell electrolysis. The Nyquist plots and equivalent circuit analysis reveal that the NiCoOx (1:3) catalyst exhibits lower activation resistance and higher efficiency in oxygen evolution reaction compared to other catalyst compositions. Temperature-dependent measurements demonstrate decreased resistances (ohmic, activation, and membrane) with increasing temperature, indicating improved reaction kinetics and ion conductivity. Long-term durability tests reveal the stable operation of the catalyst, while short-term tests confirm its effectiveness at higher current densities for single-cell electrolyzer operation. These findings highlight the importance of electrochemical Impedance Spectroscopy (EIS) and equivalent circuit fitting in optimizing AEM water electrolysis performance, aiding the development of efficient and durable electrolyzers for hydrogen production.

New Insights and Strategies for the Efficient Use of Conjugated Porous Polymers in Photoelectrochemical Solar Fuel Production

Solar energy conversion into fuels such as hydrogen through photoelectrochemical (PEC) cells is an attractive way to solve the problems present in the actual energetic system. (1) Despite the advances that have been made in this line, it is still necessary to develop new materials and cell configurations to take this technology to a higher scientific level. The application of organic polymers in PEC is a hot topic that continues to grow due to the promising optoelectronic properties of this class of semiconductors. Conjugated polymers exhibit advanced properties because of it particular conjugation that confers it a huge conductivity through the whole structure. (2) In particular, Conjugate Porous Polymers (CPP) offers a higher photostability and robustness that is fundamental for long term application, but their synthesis often leads to a large-particle powder, unsuitable for preparing thin films, key to preparing high-quality thin films, limiting its applicability in PEC.(3)In this work, we present two innovative strategies that allow the efficient use of these materials in photoelectrochemical cells. The first consists of a synthetic route through mini or ultra-mini emulsion synthesis that provides particles from 500 nm to 20 nm, adequate for thin film preparation. The second consists in the design of suitable monomers to be electropolymerised, obtaining high quality thin films and highly controlled thickness. These strategies allow the complete characterization of the optoelectronic properties of the CPPs, since the thin films obtained are of high quality and stable over time. In this way, several polymers have been prepared and the electronic structure was determined by a combination different techniques such as XPS, electrochemistry and UV-VIS spectroscopy, revealing the suitability to be used as photoelectrodes.The photoelectrochemical properties were analyses by means of linear sweep voltammetry, chronoamperometry, and Photopotential measurements suggesting its potentiality for solar energy conversion. In addition, attending o the conductivity type and electronic properties, both photoelectrodes and tandem cells have been designed by combining them with different materials such as TiO2. The formed hybrid photoelectrodes have been characterized by X-ray diffraction, SEM, EDX and AFM. A series of photoelectrochemical measurements have been performed in a three electrode cell configuration, using the hybrid materials as working electrodes. (4)Hybrid photoelectrodes present improved photovoltages and photocurrents compared to TiO2 and CPP alone, confirming adequate light absorption and charge transfer between them. Besides, Electrochemical Impedance Spectroscopy (EIS) was performed to confirm the improved charge transfer observed when illuminating the hybrid photoelectrodes. Furthermore, the designed tandem cells were connected to a gas chromatograph and the hydrogen evolution was confirmed and quantified. Keywords: Photoelectrochemistry, Solar fuels, Organic materials, Conjugate Porous Polymers, References M. Grätzel, Photoelectrochemical cells. Nature. 414, 338–344 (2001).M. Liras, M. Barawi, V. A. de la P. O’Shea. Chem. Soc. Rev. 48, 5454–5487 (2019).M. Barawi, L. Collado, M. Gomez-Mendoza, F. E. Oropeza, M. Liras, V. A. de la P. O’Shea, C. Adv. Energy Mater. 18, 2101530 (2021).M. Barawi, E. Alfonso-González, C.G. López-Calixto, A. García, A. García-Sánchez, I. J. Villar-García, M. Liras, V.A. de la Peña O'Shea. Small, 18, 37. 2201351 (2022). Acknowledgements This work was supported by the Spanish national project NovaCO2 (PID2020-118593RB-C22) and ERC POC (NanoCPP). M.B thanks the Juan de la Cierva Incorporación grant (IJC2019 – 042430 –I).

Zirconium (Oxy)Nitrides for (Photo)Electrochemical Applications

Transition metal (TM) nitrides are an emerging class of (photo)electrocatalytic materials that have recently received growing research interest.1,2 In general, nitrogen-poor TM nitrides are usually refractory materials with metallic character while nitrogen-rich nitrides often possess semiconducting character.3 Hence, while the former are potential electrocatalyst candidates, the latter may qualify as photoelectrode absorber materials. For example, ZrN has recently been proposed as an electrocatalyst for both the electrochemical nitrogen4 and oxygen5 reduction reactions (ORR and NRR), while Zr3N4 and also Zr2N2O have been suggested as potential photoanode materials in photoelectrochemical water oxidation.2 In this contribution, we test these hypotheses regarding the (photo)electrochemical characteristics of Zr-based (oxy)nitrides by experiment. To this end, we investigate reactively sputtered thin films for the electrochemical NRR/ORR and the photoelectrochemical oxygen evolution reaction (OER). Previous experiments on Ta-based nitrides have shown that addition of oxygen during the reactive sputter process is necessary to access higher metal oxidation states.6 As we introduce controlled amounts of oxygen at otherwise fixed deposition conditions, we observe a transition from metallic ZrN to a disordered nitrogen-rich ZrxNy to a crystalline bixbyite-type Zr2N2O to nitrogen-doped cubic ZrO2. Crystalline Zr3N4 was not accessible under the used experimental conditions. In our experiments, we observe a lack of electrocatalytic activity for ZrN in NRR and ORR and instabilities of the disordered nitrogen-rich ZrxNy in the photoelectrochemical OER. Introducing more oxygen into the structure, however, leads to a more stable crystalline structure (Zr2N2O), the opening of a band gap in the visible range, and the emergence of photoelectrochemical activity for oxidation reactions. Based on chopped linear sweep voltammetry measurements, we show that Zr2N2O films are photoactive for the OER in alkaline electrolyte with low onset potentials, indicating an overall favorable band alignment of the material with respect to the water oxidation and reduction potentials. While the observed photocurrents are still about one order of magnitude lower than for the benchmark oxynitride photoanode TaON, further material optimization could potentially close this gap and provide a materials system functioning as sustainable photoanode.References 1 W. Sun, C.J. Bartel, E. Arca, S.R. Bauers, B. Matthews, B. Orvañanos, B.R. Chen, M.F. Toney, L.T. Schelhas, W. Tumas, J. Tate, A. Zakutayev, S. Lany, A.M. Holder, and G. Ceder, Nat. Mater. 18, 732 (2019). 2 Y. Wu, P. Lazic, G. Hautier, K. Persson, and G. Ceder, Energy Environ. Sci. 6, 157 (2013). 3 A. Salamat, A.L. Hector, P. Kroll, and P.F. McMillan, Coord. Chem. Rev. 257, 2063 (2013). 4 Y. Abghoui, A.L. Garden, J.G. Howalt, T. Vegge, and E. Skúlason, ACS Catal. 6, 635 (2016). 5 Y. Yuan, J. Wang, S. Adimi, H. Shen, T. Thomas, R. Ma, J.P. Attfield, and M. Yang, Nat. Mater. 19, (2019). 6 C.M. Jiang, L.I. Wagner, M.K. Horton, J. Eichhorn, T. Rieth, V.F. Kunzelmann, M. Kraut, Y. Li, K.A. Persson, and I.D. Sharp, Mater. Horizons 8, 1744 (2021).

Unraveling the Synergistic Mechanism of Boosted Photocatalytic H2O2 Production over Cyano-g-C3N4/In2S3/Ppy Heterostructure and Enhanced Photocatalysis-Self-Fenton Degradation Performance.

In this work, cyano contained g-C3N4 comodified by In2S3 and polypyrrole (C≡N─CN/IS/Ppy) materials are synthesized for the photocatalytic production of H2O2 and photocatalysis-self-Fenton reaction for highly efficient degradation of metronidazole. The results from UV-vis spectrophotometry, surface photovoltage, and Kelvin probe measurements reveal the promoted transport and separation efficiency of photoinduced charges after the introduction of In2S3 and Ppy in the heterojunction. The existence of a built-in electric field accelerates the photoinduced charge separation and preserves the stronger oxidation ability of holes at the valence band of C≡N─CN. Linear sweep voltammetry measurements, zeta potential analyzations, nitroblue tetrazolium determination, and other measurements show that Ppy improves the conversion ratio of •O2 - to H2O2 and the utilization ratio of •O2 -, as well as suppresses decomposition of H2O2. Accordingly, the H2O2 evolution rate produced via a two-step single-electron reduction reaction reaches almost 895µmol L-1 h-1, a value 80% and 7.2-fold higher than those obtained with C≡N─CN/IS and C≡N─CN, respectively. The metronidazole removal rate obtained via photocatalysis-self-Fenton reaction attains 83.7% within 120 minutes, a value much higher than that recorded by the traditional Fenton method. Overall, the proposed synthesis materials and route look promising for the H2O2 production and organic pollutants degradation.

Architecture design of TiO2 with Co-doped CdS quantum dots photoelectrode for water splitting.

Photoelectrochemical hydrogen production is a critical key to solving the carbon-zero goal of countries due to renewable sources of solar light and combustion products of hydrogen-only water. Here, an architecture design for an n-type nano rosettes-rod TiO2 (RT) surface using CdS and Co-doped CdS quantum dots (QDs) is carried out utilizing the SILAR (simple ionic layer adsorption and reaction) method. Furthermore, the photocatalytic behaviour of Co-doped CdS QDs SILAR cycles deposition is investigated in various cycles, including 5, 8, 10, and 12. The FESEM, Raman XRD, Uv-Vis spectrometer, and vibration modes are used to evaluate the photoelectrode surface structure, crystal structure, and solar light absorption, respectively. FESEM images and XRD pattern revealed successive CdS QDS and Co-doped CdS QDs deposition on the RT boundary and rising SILAR cycles of Co-doped CdS QDs lead to further coverage of RT surface. UV-vis spectrometer indicated shifting solar light absorption to the visible region by applying more SILAR cycles of Co-doped CdS QDs deposition. The electrochemical parameters obtained from EIS showed total polarization resistance (Rp) of the RT electrode dramatically decreased with 10 SILAR cycle Co-doped CdS QDs deposition (5093 Ω cm2 and 617 Ω cm2). Linear sweep voltammetry (LSV) and chronoamperometric photocatalytic performance measurements indicated Co-doped CdS QDs on RT extremely enhanced photoresponse under solar irradiation and 10 SILAR cycle Co-doped CdS QDs improved photocurrent density about fourfold according to blank RT electrode.

Fabrications of the Flexible Non-Enzymatic Glucose Sensors Using Au-CuO-rGO and Au-CuO-rGO-MWCNTs Nanocomposites as Carriers.

A flexible, non-enzymatic glucose sensor was developed and tested on a polyethylene terephthalate (PET) substrate. The sensor's design involved printing Ag (silver) as the electrode and utilizing mixtures of either gold-copper oxide-modified reduced graphene oxide (Au-CuO-rGO) or gold-copper oxide-modified reduced graphene oxide-multi-walled carbon nanotubes (Au-CuO-rGO-MWCNTs) as the carrier materials. A one-pot synthesis method was employed to create a nanocomposite material, consisting of Au-CuO-rGO mixtures, which was then printed onto pre-prepared flexible electrodes. The impact of different weight ratios of MWCNTs (0~75 wt%) as a substitute for rGO was also investigated on the sensing characteristics of Au-CuO-rGO-MWCNTs glucose sensors. The fabricated electrodes underwent various material analyses, and their sensing properties for glucose in a glucose solution were measured using linear sweep voltammetry (LSV). The LSV measurement results showed that increasing the proportion of MWCNTs improved the sensor's sensitivity for detecting low concentrations of glucose. However, it also led to a significant decrease in the upper detection limit for high-glucose concentrations. Remarkably, the research findings revealed that the electrode containing 60 wt% MWCNTs demonstrated excellent sensitivity and stability in detecting low concentrations of glucose. At the lowest concentration of 0.1 μM glucose, the nanocomposites with 75 wt% MWCNTs showed the highest oxidation peak current, approximately 5.9 μA. On the other hand, the electrode without addition of MWCNTs displayed the highest detection limit (approximately 1 mM) and an oxidation peak current of about 8.1 μA at 1 mM of glucose concentration.

Electrochemical Characterization of Pd-Based Catalysts Deposited on Yittria Stabilized Zirconia Solid Electrolyte for Methane Oxidation Reaction

Methane, the main constituent of natural gas, has received increased attention since it has a higher energy density than other fossil fuels while producing less particulates containing sulphur and nitrogen. However, although methane emits less CO2 than other fossil fuels, it has 28 times more global warming potential [1]. Therefore, complete methane oxidation via heterogeneous catalysis that prevents escaping unburned methane from the engine exhaust is a key solution to this issue.Palladium is the most effective conventional noble metal for methane catalytic oxidation, which is susceptible to deactivation, especially in the presence of water. The stability and activity of a monometallic Pd catalyst could be improved upon adding a second less expensive and more abundant non-noble metal or metal oxide[2]. The interaction of Pd nanoparticles and the second metal can be characterized using electrochemical means to understand the catalytic and electrocatalytic activity of catalysts[3,4].In this work, the electrochemical behaviour of PdM (M= Co, Sn, Fe and ZnO) nanoparticles deposited on YSZ solid electrolyte was evaluated for complete methane oxidation and compared to free-standing Pd catalyst. To this end, the nanoparticles were synthesized via the polyol method and tested for their open circuit catalytic oxidation and electrochemical performance in a temperature range from 320 to 400 °C under reducing, stoichiometric and oxidizing reaction conditions.The light-off experiments in open circuit condition revealed that the presence of Sn increased the catalytic rate of the reaction more than two other metals, Co and Fe, which resulted in lowering the reaction rate per unit mass of active catalyst. Furthermore, ZnO-supported Pd demonstrated the highest catalytic reactivity due to metal-support interactions. Lastly, the results demonstrate a higher level of catalytic reactivity with higher temperatures and oxygen partial pressures (pO2).Using Tafel plot calculations from the linear sweep voltammetry measurements, the exchange current density (io) was obtained for each catalyst, as well as the apparent activation energy of the reaction in the individual condition. It was found that higher exchange current density corresponds to lower open circuit catalytic rates.The catalyst was characterized thoroughly by several physicochemical techniques, such as TEM, SEM, XRD and ICP-MS.

(Invited) Dilute Anion Alloyed III-Nitride Nanowires for Photoelectrochemical Water Splitting

The record efficiencies in photovoltaic devices and hydrogen production via photoelectrochemical water splitting have been achieved in both cases by employing complex architectures of III-V alloys 1, which has been enabled by the outstanding charge carrier transport properties, band gap and band edge engineering flexibility, as well as highly mismatch growth that can be achieved in III-V alloys by controlling their chemical composition.It has been extensively demonstrated that Molecular Beam Epitaxy (MBE) and Metal-Organic Physical Vapor Deposition (MOPVD) techniques can produce III-V multinary alloys with compositions beyond miscibility gaps due to their “far from equilibrium” nature. And although great progress has been made towards improving the growth rate in these techniques, III-V device synthesis cost is still significantly higher (one order of magnitude) than Si solar cells manufacturing technologies 2. In this context, it is necessary to develop novel synthesis methods that yield high crystalline quality III-V alloys, higher throughput, and lower operational cost. For instance, Hydride/Halide Vapor Phase Epitaxy HVPE-grown GaAs top cell incorporated in a GaAs/Si tandem cell is an example of an optimized photovoltaic device with 31.4% efficiency, showcasing the uttermost potential of this growth method 2.More recently, Halide Vapor Phase Epitaxy growth of GaSbzP1-z polycrystalline free-standing films with up to 6.7% antimony incorporation and growth rates around 500 µm/h has been reported3. Linear sweep voltammetry measurements in 1M H2SO4 using GaSbzP1-z photoanodes showed lower onset potentials and higher fill factors compared to single crystal GaP. These results have been attributed to the visible light absorbing capabilities (direct band gaps between 2.2 and 2.5 eV), and lower charge transfer resistance at the semiconductor/electrolyte interface.On the other hand, a novel method for gallium nitridation involving plasma-activated nitrogen species dissolution into molten gallium has enabled the growth of single crystal GaN4. Furthermore, dilute anion Ga-Nitride alloys have been synthesized with the same technique but including other V-group species ions, i.e., Sb+ and Bi+, that can substitute nitrogen forming ternary GaSbxN1-x and GaBiyN1-y.In this presentation, we show the progress with dilute anion alloyed III-Nitride nanowires, GaSbxN1-x and GaBiyN1-y, synthesized by dissolving gallium, antimony or bismuth and plasma-activated nitrogen species into copper or gold droplets. Antimony and bismuth incorporation levels determined through x-ray diffraction c-plane peak shift, x and y, reached levels as high as 5.6 and 8.8 at%, respectively, resulting in direct band gap energies around 2.0 eV, determined through diffuse reflectance and photocurrent spectroscopy measurements. The visible light absorbing nanowire films exhibited photocurrent onset potentials around 0.0 V vs RHE when tested in 1 M sulfuric acid solution and 3-electrode setup with Ag/AgCl reference and Pt counter electrodes. 2-electrode chronoamperometry measurements with p-Si and n-type dilute alloys showed stable photocurrent densities up to 8.5 mA*cm-2 in 30 h. These results show the promising potential of dilute anion alloyed III-Nitrides as stable photoanodes for water splitting applications, and demonstrate the advantage of this novel synthesis technique over MOCVD that in previous studies has enabled the obtention of 0-D or 1-D GaSbxN1-x structures with up to 7% anion incorporation, while compromising crystalline quality.5

Dependence of deposition bath temperature for p-electrodeposited-Cu2O onto n-TiO2/ZnO bilayer thin films

The synthesis of semiconductor materials is crucial to produce the best properties of heterojunction thin films solar cell. Titanium dioxide (TiO2) is coupled with zinc oxide (ZnO) to promote high transmittance due to low utilization of the solar spectrum. In this project, p-Cu2O as absorbing layer was deposited onto n-TiO2/ZnO bilayer thin film which acts as window layer in order to complete the device. Several bath temperatures of 30, 40, 50 and 60 °C were manipulated during Linear Sweep Voltammetry (LSV) measurement and electrodeposition process for p-Cu2O thin film. The LSV measurement was employed to determine the potential value and electrochemical properties of p-Cu2O thin film. Based on findings, the suitable deposition potential chosen is − 0.4 V vs Ag/AgCl. The p-Cu2O thin film deposited at bath temperature of 40 °C exhibited the highest diffraction peak intensity in the (111)-preferred plane orientation showing high crystallinity. The surface morphology of homogeneous and well-defined triangular shape with thickness of 4.93μm was observed. The estimated bandgap energy of 1.92 eV acquired indicated to p-Cu2O thin film. The n-TiO2/ZnO bilayer/p-Cu2O heterojunction thin film was successfully fabricated and showed significant electrical rectification properties. Here in, bath temperature influenced to the enhancement of heterointerface growth development in several properties.