Two-electrode System Research Articles

Crystalline Ni5P4/amorphous CePO4 core/shell heterostructure arrays for highly-efficient electrocatalytic overall water splitting

Exploring low-cost and highly efficient bifunctional electrocatalysts for overall water splitting has become a research focus recently. Crystalline/amorphous core/shell heterostructures have great potential for applications in the field of electrocatalytic overall water splitting. However, related research is still challenging. Herein, crystalline Ni5P4 nanosheets/amorphous CePO4 nanocrystals core/shell heterostructure arrays were developed for electrocatalytic overall water splitting. It is shown that the heterostructure array required competitive HER and OER overpotentials of 94 and 191 mV in alkaline environment (10 mA/cm2), respectively. Encouragingly, the symmetrical two-electrode system constructed with the heterostructure array only required an ultra-low cell voltage of 1.535 V to achieve a current density of 10 mA/cm2. This indicates the system has huge potential in overall water splitting. The electrocatalytic mechanism was studied systematically by combining theoretical calculation and experimental characterization. It was found that the surface coating of amorphous CePO4 could not only significantly increase the electrochemical active surface area and improve the charge transfer of crystalline Ni5P4 nanosheets, but could also regulate d-band center of Ni5P4 and optimize the adsorption towards reaction intermediates in water splitting. The results not only provide an excellent crystalline/amorphous core/shell heterostructure bifunctional electrocatalyst for overall water splitting but also greatly expand the application of rare earth metal phosphate CePO4.

Conducting polymer wrapped SnO2/RGO nanocomposite: An efficient high-performance supercapacitor material

This study describes a ternary poly (3,4-ethylenedioxythiophene)-poly-(styrenesulfonate) (PEDOT:PSS)-wrapped tin oxide/reduced graphene oxide (SnO2/RGO/PEDOT: PSS) (SGP) nanocomposite electrode as a supercapacitor electrode. The properties of the SGP nanocomposites were studied using various characterization techniques such as X-ray Diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), Raman spectroscopy, and electrochemical impedance spectroscopy. The XRD results demonstrated the reduction of graphene oxide during the synthesis. TEM analysis confirmed the presence of PEDOT: PSS and graphene layers adorned with minuscule SnO2 particles. Standard three-electrode geometry was used to investigate the electrochemical properties of the samples. For comparison, a two-electrode system was used to investigate the electrochemical properties. The as-prepared SGP nanocomposite electrode exhibited specific capacitance of 252.0 F/g and 124 F/g at a scan rate of 1 mV/s for the three-electrode and two-electrode systems, respectively. Furthermore, the electrode retained approximately 97.8 % of its capacitance even after 5000 cycles. However, the SGP electrode when operated to wide voltage window -0.6 V to +0.6 V exhibited the maximum specific capacitance of 285.0 F/g at scan rate 1 mV/sec and shows 114 % enhancement in the capacitance retention after the 5000 cycles at current density of 10 A/g which gives a protocol for future energy storage device application with high operating voltage. The SGP-based supercapacitor exhibited a high energy density (17.7 Wh kg −1) and power density (1220 W kg −1).

Iron-doped cobalt nitride as an efficient electrocatalyst towards energy saving hydrazine assisted seawater splitting in near neutral to highly alkaline pH achieving industry level current density

Replacing sluggish anodic oxygen evolution reaction by hydrazine oxidation reaction in seawater electrolysis is one of the smartest ways of getting multiple benefits as it offers an energy saving route for hydrogen production keeping the cell voltage way smaller than responsible voltage for corrosive chloride oxidation. Here, we report iron-doped Co3N as highly active electrocatalyst towards hydrazine oxidation reaction and hydrogen evolution reaction in wide pH range of 7–14. The two-electrode electrolyser system reached industry scale current density of 1000 mA cm−2 at ultralow cell voltage of 0.65 V, and found sustainable at 500 mA cm−2 over 95 h in hydrazine assisted alkaline seawater splitting. The electrolyser system also achieved 200 mA cm−2 current density at 0.75 V in hydrazine assisted neutral seawater medium. Interestingly, a thin amorphous iron oxide layer formed in Fe-doped Co3N provided much needed protection during electrocatalysis offering long term stability at industry level current density.

Synthesis of water-soluble nitrogen doped carbon quantum dots-polypyrrole nanocomposite via in-situ polymerization for high performance supercapacitor application

In this work, water-soluble nitrogen doped carbon quantum dots (NCQDs) were synthesized via a hydrothermal approach, and nitrogen doped carbon quantum dots-polypyrrole nanocomposites (NCQDs/PPy) were synthesized using In-Situ chemical polymerization methods. The synthesized pure NCQDs, PPy, and NCQDs/PPy nanocomposites are characterized with help of X-ray diffractometry (XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscope (FESEM), Ultraviolet-Visible (UV–Vis) spectroscopy, and Raman spectroscopy techniques to study their chemical changes, structural phase, morphology, and optical properties. The electrochemical performance is investigated through a two-electrode system, and the NCQDs/PPy-2 nanocomposite shows a high specific capacitance (Csp) of 750 Fg−1 at a current density (CD) of 1 Ag−1 with a wide operating potential window from −0.8 V to 0.8 V. In addition, the fabricated symmetrical device shows an energy density (ED) of 43.47 Whkg−1 and a high-power density (PD) of 3129.84 Wkg−1. Besides, the NCQDs/PPy-2 shows a higher cycle life span with 77.82 % of capacitance retention and 97.04 % of coulombic efficiency even after 8000 charging and discharging cycles. These findings demonstrate that NCQDs/PPy-2 nanocomposite material is a highly prominent electrode material for supercapacitor applications.

Nanostructured Pt@RuOx catalyst for boosting overall acidic seawater splitting

In the domain of acidic water splitting, designing bifunctional catalysts that marry high activity with enduring stability is a formidable challenge. Herein, we have constructed platinum-containing ruthenium oxide nanoparticles (Pt@RuOx NPs) to achieve excellent overall water splitting performance in acidic electrolytes. Pt@RuOx NPs demonstrate exceptional catalytic activity for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acidic seawater, requiring overpotentials of only 20 and 157 mV, respectively to achieve a current density of 10 mA cm−2. Furthermore, in 0.5 M H2SO4, this catalyst exhibits high HER (19 mV) and OER (236 mV) catalytic activities. The two-electrode water splitting system composed of bifunctional Pt@RuOx NPs requires cell voltages of only 1.442 and 1.465 V to deliver a current density of 10 mA cm−2 in acidic seawater and 0.5 M H2SO4. Remarkably, this catalyst displays remarkable stability in the water splitting process. It is shown that the introduction of Pt could augment oxygen vacancies and enhance catalytic activity significantly. The synergy between Pt and Ru further contributes to the improved performance. Additionally, we have observed that acidic seawater holds distinct advantages for acidic water splitting, along with a thorough exploration of the relationship between Cl− concentration and catalytic performance. This study not only provides a strategy to improve the catalytic activity and stability of ruthenium-based catalysts for water splitting in acidic environments, but also unveils the promoting effect of Cl− on the catalytic activity in acidic water splitting.

Enhanced hydrogen production via urea electrolysis over Ni-NiO electrodeposited on Ti mesh

The sluggish kinetics of anodic oxygen evolution reaction (OER) is regarded as the main bottleneck for ineffective hydrogen production efficiency, limiting the industrial application of electrochemical water splitting. Substituting the OER by urea electrooxidation reaction (UOR) and simultaneously developing highly active and economical bifunctional electrocatalyst for UOR and hydrogen evolution reaction (HER) is a promising method to realize energy-saving hydrogen production and urea-rich wastewater abatement. Herein, self-supporting Ni-NiO film grown on Ti mesh (Ni-NiO/TM) was successfully prepared by a facile cathodic electrodeposition method with using nickel acetate as the only raw material. Electrodeposition process was optimized by modulating the electrodeposition time and potential. x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and Raman characterization revealed the optimized Ni-NiO/TM was comprised of crystalline Ni and amorphous NiO and its morphology exhibited nanosphere structure, assembled by nanosheets. Ni-NiO/TM sample prepared under the potential of −1.5 V and deposition time of 10 min illustrated the lowest UOR potential of 1.34 V at 50 mA cm−2 and robust stability, superior to the recently reported literatures. Furthermore, the HER potential was only −0.235 V to drive the current density of 50 mA cm−2. The cell voltage of urea-assisted electrolysis for hydrogen production in Ni-NiO/TM||Ni-NiO/TM two-electrode system only required 1.56 V to deliver 50 mA cm−2, obviously lower than that (>1.72 V) for overall water splitting. This work demonstrated the potential of Ni-based material as bifunctional electrocatalyst for energy-saving H2 production by urea-rich wastewater electrolysis.

Double active sites promoting hydrogen evolution activity and stability of CoRuOH/Co2P by rapid hydrolysis

Cobalt-based phosphides show excellent hydrogen evolution reaction (HER) performance, however, improving the intrinsic activity and stability of it in alkaline electrolyte still remains a challenge. Herein, CoRuOH/Co2P/CF with heterojunction structure was developed by means of molten salt and rapid hydrolysis (30 s). The OH− from rapid surface hydrolysis of Co2P as a hydrogen adsorption site can facilitate the formation of thin CoRuOH layer as a water dissociation site, which may bring out better synergistic effect for alkaline HER. Moreover, the covering of CoRuOH can improve the stability of Co2P for HER. When drives at 100 mA/cm2, it only requires overpotential of 81 mV in 1.0 mol/L KOH (25 °C). Even at higher current density (1000 mA/cm2), CoRuOH/Co2P/CF can also operate stability for at least 100 h. When coupling with NiFe-LDH/IF in a two-electrode system, the voltage of NiFe-LDH/IF(+) || CoRuOH/Co2P/CF(−) at 1000 mA/cm2 is merely 1.77 V with 100 h, demonstrating great potential for water splitting. The implementation of this work provides a new strategy and reference for the further improvement of transition metal phosphides as HER electrocatalysts.

One-step fabrication of N/O self-doped porous carbon derived from 2-MeIM for high-performance supercapacitor electrode

Doping engineering is a high-efficiency strategy to introduce heteroatom species and modify the surface electronic structures of porous carbon materials. However, the conventional doping strategies for porous carbons usually involve with either complicated fabrication processes or difficulty in quality control. Herein, nitrogen‑oxygen self-doped porous carbons (NOPCs) with adjustable structure are prepared by a facile one-step process of direct carbonization/activation the mixture of 2-methylimidazole (2-MeIM) and KOH. The as-prepared NOPCs possess hierarchical porous structure with interconnected micro-/meso-/macropores, high specific surface area (2900 m2 g−1), large pore volume (1.2 cm3 g−1) and high N,O heteroatoms level (26.8 at.% in total), which exhibit ultra-high specific capacitance of 424.2 F g−1 at 1.0 A g−1 in a three-electrode system in 2 M KOH electrolyte and 173.4 F g−1 at 1.0 A g−1 in a two-electrode system in EMIMBF4 ionic liquid electrolyte. Impressively, the symmetric supercapacitor based on NOPC exhibits a wide operating voltage window up to 3 V, a high energy density of 56.4 Wh kg−1 at a power density of 373.6 W kg−1, excellent rate performance with the retention of ~76.2 % from 1.0 to 100 A g−1, and splendid cycling stability with only 0.0011 % capacity fading per cycle within 10,000 loops. Consequently, the one-step carbonization/activation strategy with commercial-available 2-MeIM as raw material is promising for mass production of high performance NOPC materials.

Electrochemically Oxidized Carbon Nanotube Sheets for High-Performance and Flexible-Film Supercapacitors.

The development of flexible, high-performance supercapacitors has been a focal point in energy storage research. While carbon nanotube (CNT) sheets offer promising mechanical and electrical properties, their low electrical double-layer capacitance significantly limits their practicability. Herein, we introduce a novel approach to address this challenge via the electrochemical oxidation treatment of CNT sheets stacked on a polyethylene terephthalate substrate. This introduces oxygen-containing functional groups onto the CNT surface, thereby dramatically enhancing the pseudocapacitive effect and improving ion adsorption. Consequently, using the material in a two-electrode system increased the capacitance by 54 times compared to pristine CNT. The results of electrochemical performance characterization, including cyclic voltammograms, galvanostatic charge/discharge curves, and capacitance retention testing data, confirm the efficacy of the electrochemical oxidation approach. Furthermore, the mechanical flexibility of the electrochemically wetted CNT sheets was validated through resistance and discharge retention testing under repetitive bending (98% capacitance retention after 1000 bending cycles). The results demonstrate that electrochemically wetted CNT sheets retain their intrinsic mechanical and electrical properties while significantly enhancing the electrochemical performance (0.59 mF/cm2 or 97.8 F/g). This work represents a significant advancement in the development of flexible, high-performance supercapacitors with potential applicability to wearable electronics, flexible displays, and next-generation energy storage solutions.

Activated carbon derived from Satureja seed biomass for improving the capacitive performance of composite based on Aprepitant functionalized graphene oxide and ionic liquid

In this work, three chemicals, including Aprepitant functionalized graphene oxide (APR-FGO), PhenmimCl ionic liquid (IL), and activated carbon derived from Satureja seed (AC-SS), were synthesized and used in a supercapacitor system as electrode materials. After the structural description of the synthesized materials, the electrochemical performance of APR-FGO, APR-FGO/AC-SS, and APR-FGO/AC-SS/IL electrodes was investigated in a three-electrode system. Based on the comparison of electrochemical results, the APR-FGO/AC-SS/IL electrode was able to provide the best performance compared to the other two electrodes. It was observed that the APR-FGO/AC-SS/IL electrode presented the specific capacitance (Cs) of 493.24 F g−1 at 1 A g−1. Also, the Cs retention value of the APR-FGO/AC-SS/IL electrode was 95.2 % at 8 A g−1 over 10,000 charge-discharge cycles. Furthermore, in a two-electrode system, the APR-FGO/AC-SS/IL electrode obtained a Cs of 214 F g−1, an energy density of 32.22 Wh kg−1, and a power density of 850 W kg−1 at 1 A g−1. These findings prove the ideal electrochemical performance of this composite as a supercapacitor electrode. The superior performance of the APR-FGO/AC-SS/IL electrode can be attributed to the presence of groups containing nitrogen and fluorine in the Aprepitant functionalized graphene oxide structure, the essential role of AC-SS as a substrate for performing electrochemical reactions, and the high conductivity of the PhenmimCl ionic liquid. Therefore, the proper synergy of these three materials shows that the APR-FGO/AC-SS/IL electrode has a high potential for energy storage systems.

Bifunctional Ni Foam Supported TiO2 @Ni3 S2 core@shell Nanorod Arrays for Boosting Electrocatalytic Biomass Upgrading and H2 Production Reactions.

Replacing traditional oxygen evoltion reaction(OER) with biomass oxidation reaction (BOR) is an advantageous alternative choice to obtain green hydrogen energy from electrocatalytic water splitting. Herein, a novel of extremely homogeneous Ni3 S2 nanosheets covered TiO2 nanorod arrays are in situ growth on conductive Ni foam (Ni/TiO2 @Ni3 S2 ). The Ni/TiO2 @Ni3 S2 electrode exhibits excellent electrocatalytic activity and long-term stability for both BOR and hydrogen evolution reaction (HER). Especially, taking glucose as a typical biomass, the average hydrogen production rate of the HER-glucose oxidation reaction (GOR) two-electrode system reached 984.74µmol h-1 , about 2.7 times higher than that of in a common HER//OER two-electrode water splitting system (365.50µmol h-1 ). The calculated power energy saving efficiency of the GOR//HER system is about 13% less than that of the OER//HER system. Meanwhile, the corresponding selectivity of the value-added formic acid produced by GORreaches about 80%. Moreover, the Ni/TiO2 @Ni3 S2 electrode also exhibits excellent electrocatalytic activity on a diverse range of typical biomass intermediates, such as urea, sucrose, fructose, furfuryl alcohol (FFA), 5-hydroxymethylfurfural (HMF), and alcohol (EtOH). These results show that Ni/TiO2 @Ni3 S2 has great potential in electrocatalysis, especially in replacing OER reaction with BOR reaction and promoting the sustainable development of hydrogen production.

Bifunctional carbon quantum dot-embedded metal-organic framework nanohybrid as a highly efficient electrocatalyst for water splitting and CO2 reduction

Bifunctional carbon quantum dot (CQD)-embedded metal-organic framework (MOF) (CQD@MOF) nanohybrid as an energy-efficient electrocatalyst is fabricated for electrochemical water splitting and CO2 reduction through a simple and environmentally friendly method using natural resources. Key parameters, such as synthesis temperature, deposition temperature and time, pH and type of electrolyte, and scan rate, are optimized to fabricate binder-free CQD@MOF/nickel foam (NF) electrodes. Excellent hydrogen and oxygen evolution reactions occur with a current density of 50 mA/cm2 at lower overpotentials of 48.00 and 135 mV in a 1 M potassium hydroxide (KOH) electrolyte at a scan rate of 5 mV/s, respectively. In a two-electrode system, the CQD@MOF/NF electrode exhibits a low overpotential of 1.36 V to achieve 10 mA/cm2, confirming the practical feasibility of overall water splitting. Furthermore, the electrode exhibits high chemical stability and robustness even after 4000 cycles and more than 17 h. These results are attributed to the effective combination of substantial adsorption sites and the improved conductivity of the MOF induced by the electron-accepting characteristics of the CQDs with high charge transfer rates during water splitting. Finally, electrochemical CO2 reduction of the CQD@MOF/NF electrode is demonstrated by continuously maintaining a specific current density for 12 h, which can extend the technological potential of carbon nanohybrid as an electrocatalyst for green energy applications.

Nano-casting synthesis of nanoporous carbons from biomass tar as sustainable electrode material for high-performance supercapacitor

Asphalt and coal tar, etc., as byproducts from fossil refinery featured with polycyclic carbon, are hot precursors for diverse advanced carbon functional materials. Herein, their bio-counterpart, namely biomass tar (BT), a notorious byproduct from biomass pyrolysis/gasification was successfully converted into O, N-co-doped carbon with interconnected porous structure via nano-casting with ZnO nano-rods. The optimal product obtained at 700 °C with mass ratio of 1:2:2 for biomass tar, nano-ZnO and KOH delivered specific capacitance up to 295F/g and 204F/g at current densities of 1 A/g and 20 A/g, respectively, and the specific capacitance was maintained at 86.3 % after 10,000 cycles of charging-discharging at 20 A/g. In the two-electrode system, a single electrode made of BTC-1Z-2K-700 still has a specific capacitance of 295.2 F/g at 0.2 A/g. Symmetrical supercapacitor device assembled with 1 M Na2SO4 as the electrolyte achieves the energy density of 27.19 Wh/kg at the power density of 640 W/kg. The impressive charge storage capacity and rating performance were attributed to its hierarchical porosity, large interface and low electric resistance. This work provides a novel out path for biomass tar valorization, as well as a sustainable and cost-effective candidate for electrode material for high-performance supercapacitor.

Fabrication of CH3NH3SnCl3 perovskite nanocrystal-based electrode for supercapacitor devices application

Lead-free halide perovskites nanocrystals (NCs) have been widely used not only in the field of optoelectronics but also in energy storage applications like electrochemical supercapacitors, which could replace electrochemical batteries due to their high power density and long cycle life. The low energy density of supercapacitors is one of the main reasons why they have limited commercial applications. Herein, we have reported synthesis of 3D methylammonium tin chloride perovskite (MASnCl3) nanocrystals (NCs) via a ligand-assisted re-precipitation process (LARP) and determined its performance as an electrochemical supercapacitor. The formation of MASnCl3 NCs is confirmed by different characterization tools. The supercapacitor performances of the synthesized NCs are studied by using three-electrode electrochemical measurements. The maximum specific capacitance, energy density, and power density are found to be 2050 Fg−1, 12 kWKg−1, and 102 WhKg−1, respectively. The charge storage mechanism is estimated from the power law equation by studying the diffusion-limited and capacitive processes and it has been found that the capacitance is 94.16 % capacitive to 5.84 % diffusive in nature. The supercapacitor performance of the synthesized MASnCl3 NCs are studied by fabricating a metal coin-based two-electrode system in which PVA-H2SO4 as solid state electrolyte and NCs act as an active material. The device has retained 80.7 % of its initial specific capacitance value even after 1000 GCD cycles. Interestingly, the developed device showed almost similar gravimetric capacitance value and is enabled to glow a light emitting diode (LED) smoothly.

Biomass-based porous carbon for high-performance supercapacitor electrode materials prepared from Canada goldenrod

Preparing activated carbon from biomass materials that can be used as electrode materials for supercapacitors is crucial for realizing new green energy storage and conversion technologies to fulfill environmental requirements. Herein, activated carbon was prepared via high-temperature carbonization and KOH activation using Canada goldenrod as a raw material, which is a serious threat to the ecological environment. Using this activated carbon as the active material and 6 M KOH and 1 M TEABF4/AN as the electrolytes, aqueous and organic coin-cell symmetrical supercapacitors were prepared, respectively. The specific capacitance of activated carbon was calculated to reach 320 and 123 F/g at a current density of 0.1 A/g during its testing in a two-electrode system, corresponding to energy densities of 40 and 112.1 Wh/kg, respectively. The power density of the aqueous supercapacitor was 9 KW/Kg at 10 A/g, while that of the organic supercapacitor was 12.2 KW/Kg at 5 A/g; after 10,000 cycles of the charge–discharge test, the capacity retention rate reached 93.6 % and 86.4 %, indicating the excellent electrochemical performance of the prepared supercapacitor. In addition, the specific capacitance reached 366 and 252 F/g at capacitance densities of 0.1 and 0.5 A/g, respectively, during its testing in a three-electrode system. The results of this study indicate that Canada goldenrod is a good biomass-based precursor material for preparing porous carbon for supercapacitors.

Hydrothermal synthesis of graphene oxide interspersed in non-uniform tungsten oxide nanorod and its performance towards highly efficient hybrid supercapacitor

In this study, hybrid graphene oxide/tungsten oxide nanostructures (GO/WO3 NSs) are synthesized using an eco-friendly and efficient hydrothermal method. Physicochemical analysis reveals the presence of a monoclinic phase with characteristic diffraction peaks, as indicated by the crystallinity degree. Using a field emission scanning electron microscope, heterogeneous non-uniform agglomerated nanosheets with non-uniform nanorods are observed in the GO/WO3 hybrid NSs. Results of transmission electron microscopy and X-ray photoelectron spectroscopy provide comprehensive details regarding the morphological, structural, and electronic state characteristics of the GO/WO3 hybrid NSs. Electrochemical data for GO/WO3 are obtained using an aqueous 2 M KOH electrolyte. The maximum specific capacity (Csp) and gravimetric capacitance (Cg) of the GO/WO3 are observed under 10% GO. The values of Csp and Cg are 123 mAh/g and 738 F/g, respectively, whereas the maximum energy (Ed) and power densities (Pd) are 37 Wh/kg and 500 W/kg at 5 mA/cm2, respectively. Furthermore, the optimized sample (GO-W2) shows superior capacitive retention of 88% over 7000 cyclic voltammetry cycles at a scan rate of 100 mV/s. A GO-W2-NF//GO-NF (where NF represents Ni-foam) asymmetrical hybrid liquid state device is fabricated using a two-electrode system, which demonstrates favorable electrochemical properties, i.e., Csp and Cg values of 94 mAh/g and 213 F/g at 5 mV/s respectively, and Ed and Pd values of 25 Wh/kg and 1000 W/kg at 4 mA/cm2, respectively. These findings indicate that GO/WO3 hybrid NSs are effective electrode materials for future research pertaining to energy storage systems.

1D/3D Heterogeneous Assembling Body of Cobalt Nitrides for Highly Efficient Overall Hydrazine Splitting and Supercapacitors.

Herein, the construction of a heterostructured 1D/3D CoN-Co2 N@NF (nickel foam) electrode used for thermodynamically favorable hydrazine oxidation reaction (HzOR), as an alternative to sluggish anodic oxygen evolution reaction (OER) in water splitting for hydrogen production, is reported. The electrode exhibits remarkable catalytic activities, with an onset potential of -0.11V in HzOR and -71mV for a current density of 10mA cm-2 in hydrogen evolution reaction (HER). Consequently, an extraordinary low cell voltage of 53mV is required to achieve 10mA cm-2 for overall hydrazine splitting in a two-electrode system, demonstrating significant energy-saving advantages over conventional water splitting. The HzOR proceeds through the 4e- reaction pathway to release N2 while the 1e- pathway to emit NH3 is uncompetitive, as evidenced by differential electrochemical mass spectrometric measurements. The X-ray absorption spectroscopy, in situ Raman spectroscopy, and theoretical calculations identify cobalt nitrides rather than corresponding oxides/(oxy)hydroxides as catalytic species for HzOR and illustrate advantages of heterostructured CoN-Co2 N in optimizing adsorption energies of intermediates/reagents and promoting catalytic activities toward both HzOR and HER. The CoN-Co2 N@NF is also an excellent supercapacitive material, exhibiting an increased specific capacity (938 F g-1 at 1 A g-1 ) with excellent cycling stability (95.8%, 5000 cycles).

Effect of deposition voltage on the properties of electrodeposited CdZrS thin films for solar cell application

The electrodeposition procedure was carried out utilizing a two-electrode system on fluorine-doped tin oxide (FTO) substrates, with the deposition voltage for CdS set at 1450 mV and for CdZrS at the range of 1450, 1550, and 1600 mV. The structural results show that both CdS and CdZrS thin films exhibit cubic structure. Surface image analysis shows that the FTO substrate was covered by film. The shape and grain size of the films is varied with deposition voltage. Elemental composition analysis confirmed the presence of desired elements Cd, Zr, and S on the deposited samples. CdS and CdZrS surfaces have an average surface roughness in the range of (3.2−19.6) nm. The optical properties of the films revealed a bandgap energy of 2.25 eV for CdS and (2.09−2.39) eV for CdZrS. The electrodeposited CdZrS thin films have potential applications as buffer layers in solar cell devices.

Triggering the high catalytic activity of Ni-based catalyst for urea and urine electrolysis by adding Fe and constructing the CoFeP@Ni3S2 heterostructure

For effective hydrogen production, urea oxidation reaction (UOR) with much lower potential has been used to replace the water oxidation reaction (OER), while fulfilling the wastewater treatment. Development of bifunctional electrocatalysts is the crucial link in urea-assistant water electrolysis. Here, a novel composite consisting of the bimetallic phosphide nanosheets and porous Ni3S2 nanospheres was prepared by a hydrothermal-electrodeposition method. It proves that the NF/CoFeP@Ni3S2 electrode exhibits an outstanding performance for HER/UOR (HER overpotential is 173 mV and EUOR is 1.358 V, 100 mA cm−2). As for a two-electrode system taking NF/CoFeP@Ni3S2 as cathode and anode in urea medium, the voltage at 100 mA cm−2 is just 1.454 V. Even in human urine electrolyte, just only a slight current decrease is observed. Both in urea and urine, the voltage of NF/CoFeP@Ni3S2 remain stable during a 50-hour continuous operation. The formation of heterostructures between the bimetallic phosphides and Ni3S2, and Fe addition realize the gradual improvement in activity from the pristine CoP to CoFeP and then to the CoFeP@Ni3S2. This strategy provides a practical hetero-structured catalyst design form considering the structure properties of urea molecule for the efficient water-hydrogen conversion synchronous sewage treatment.

A two-electrode frequency-scan system for gesture recognition

A two-electrode frequency-scan system for gesture recognition