Tafel Value Research Articles

Rational Design of the CdS/Fe-MOF Hybrid for Enhanced Hydrogen Evolution Reaction Catalysis

Electrochemical water-splitting is a promising method for producing sustainable and eco-friendly hydrogen as an energy source. However, it is imperative to create a durable and exceptionally effective catalyst to guarantee an optimal process efficiency. Studies have shown that transition metal sulfides and metal–organic frameworks can be effective electrocatalysts for hydrogen production. Herein, the focus is on synthesizing and investigating hybrids composed of cadmium sulfide and MIL-101(Fe) (a metal–organic framework) for hydrogen evolution reaction (HER) in an alkaline environment. The results of the study indicate that these hybrids exhibit improved activity for HER compared to pure compounds. The optimized hybrid of CdS/MIL-101(Fe) (3:1) showed a small overpotential of 108 mV to achieve a 10 mA/cm2 current density and a low Tafel value of 47 mV/dec in alkaline media. Additionally, it remained stable for 1000 cyclic voltammetry cycles and 24 h with only a minimum shift in performance. The synergistic interaction between the two functional materials is the probable cause for the improved activity of hybrids over pure compounds. The presence of MIL-101(Fe) provides increased active sites and porosity, while CdS enhances the electrical properties of the hybrid. These properties add up in the hybrid and result in an enhancement in activity. This development presents an appealing strategy for fabricating non-noble-metal electrocatalysts for hydrogen synthesis, thereby marking a noteworthy milestone in the pursuit of sustainable and eco-friendly energy production.

Silver nanoparticles embedded in phosphorus and nitrogen-doped hierarchical hollow porous carbon for efficient supercapacitor and electrocatalytic water oxidation

Supercapacitor (SC) and oxygen evolution reaction (OER) require highly efficient multifunctional catalysts prepared from non-noble metals and heteroatoms. In this work, we have developed silver (Ag) decorated on phosphorus (P), nitrogen (N) -doped hollow porous carbon (HPC) prepared through hydrothermal followed by pyrolysis method. The prepared bifunctional electrocatalyst was studied through different characterization techniques. As-prepared HPC-UD, P-HPC-UD, and [email protected] integrate high-level P-doping, large specific surface areas (up to 1452, 1247, and 528 m2 g−1), and hierarchical multipores of cross-linked micro and mesopore channels. As a result, the Ag and P modified the active sites and electronic structure of the HPC bifunctional catalyst, which is beneficial for the electrocatalytic process. As a result, the [email protected] catalyst provides an outstanding specific capacitance value of 388 F g−1 at 0.5 A g−1 when used as a SC electrode. Furthermore, the [email protected] electrocatalyst exhibited efficient OER behavior with a lower overpotential of 165 mV at 10 mA cm−2 current density and a lower Tafel value of 55.46 mV dec−1, which is remarkably superior to commercial RuO2 electrocatalyst. Therefore, the [email protected] electrocatalyst pathway for a new revolution in developing a highly impressive carbon-based electrode towards both SC and electrocatalytic OER performance.

Electrocatalytic behavior of Ni-Co-Fe3O4 nanospheres for efficient oxygen evolution reaction

Electrocatalytic behavior of Ni-Co-Fe3O4 nanospheres for efficient oxygen evolution reaction

Insight into the Co/Fe intrinsically assembled structure in cobalt-iron-layered double hydroxides on catalytic oxygen evolution reaction

Insight into the Co/Fe intrinsically assembled structure in cobalt-iron-layered double hydroxides on catalytic oxygen evolution reaction

TiO2 nanotubes modified with cobalt oxyphosphide spheres for efficient electrocatalytic hydrogen evolution reaction in alkaline medium

TiO2 nanotubes modified with cobalt oxyphosphide spheres for efficient electrocatalytic hydrogen evolution reaction in alkaline medium

Synergistic Germanium-Decorated h-BN/MoS2 Heterostructure Nanosheets: An Advanced Electrocatalyst for Energy Storage Applications

Increasing concerns about the vulnerability of the world’s energy supply and the necessity to implement sustainable technologies have prompted researchers to develop high-performance electrocatalysts that are affordable and efficient for converting and storing renewable energy. This article reports a facile approach to fabricating two-dimensional (2D) Ge-decorated h-BN/MoS2 heterostructure nanosheets by self-assembly for multiple electrochemical applications such as supercapacitor and hydrogen evolution reactions. The organization of the physical and chemical links between the germanium modulations on the heterostructure of boron nitride/molybdenum sulphide (Ge/h-BN/MoS2) were facilitated to generate more active sites. Furthermore, the asymmetric supercapacitor of Ge-decorated h-BN/MoS2 amplified the capacitance to 558.53 F g−1 at 1 A g−1 current density and 159.19 F g−1 at 10 A g−1, in addition to a retention rate of 85.69% after 2000 cycles. Moreover, the Ge-decorated h-BN/MoS2 catalyst realized a low over-potential value, with an RHE of 0.57 (HER) at 5 mA/cm2, a Tafel value of ∼204 mV/dec, and long-term electrolysis stability of 10 h. This work may open the door for further investigations on metal-decorated heterostructures, which have a significant potential for both supercapacitor and water-splitting applications.

Nitrogen doped carbon fiber supported nickel phosphide for efficient electrocatalytic overall urea splitting

Nitrogen doped carbon fiber supported nickel phosphide for efficient electrocatalytic overall urea splitting

Cl-doped CuO for electrochemical hydrogen evolution reaction and tetracycline photocatalytic degradation

Cl-doped CuO for electrochemical hydrogen evolution reaction and tetracycline photocatalytic degradation

Ultralow Fe instigated defect engineering of hierarchical N–Porous carbon for highly efficient electrocatalysis

Ultralow Fe instigated defect engineering of hierarchical N–Porous carbon for highly efficient electrocatalysis

Decorating Cu2O with Ni-doped metal organic frameworks as efficient photocathodes for solar water splitting

Decorating Cu2O with Ni-doped metal organic frameworks as efficient photocathodes for solar water splitting

Co0.75Mo3S3.75/CoS2@2D-MoS2 nanosheets on carbon cloth: A progressive binder-free electrocatalyst for hydrogen evolution reaction

The development of ultrathin non-noble metal dichalcogenide electrocatalysts with tunable physical properties such as phase transformations, defect engineering, and activating plane edges is essential in order to enhance their electrocatalytic performance for water splitting applications. In this present work, we account to report a facile approach to cationic modulations through a single-step hydrothermal approach for the fabrication of a two-dimensional (2D) self-assembled ultrathin Co0.75Mo3S3.75/CoS2 (Co–Mo–S) @MoS2 nanoflowers directly grown on carbon fibre cloth. The systematic physicochemical relationship of cobalt ion modulations into MoS2 nanoflowers (Co/Mo/S) enabled the formation of flower-like Co–Mo–[email protected]2 ultrathin nanosheets with enhanced active sites, resulting in enhanced electrocatalytic contribution for hydrogen evolution reaction. The synthesised catalyst exhibited an ultralow overpotential value of 43 mV (RHE) at 20 mA/cm2, very small Tafel value of ∼36.6 mV/dec, and long durability/stability of 51 h of electrolysis. As a whole, these presented results demonstrate a rational construction of 2D ion modulated MoS2 ultrathin nanosheet electrodes that are beneficial for sustainable energy storage devices, which could be potentially extended to other dimensional MoS2 based materials.

Vanadium-induced synthesis of amorphous V-Co-P nanoparticles for an enhanced hydrogen evolution reaction.

The hydrogen evolution reaction (HER) plays a vital role for the production of pure hydrogen with zero carbon release. Developing high efficiency non-noble metal electrocatalysts could reduce its cost. Here, vanadium doped cobalt phosphide grown on carbon cloth (CC) was synthesized by the low temperature electrodeposition-phosphorization method. The influence of V dopants on the structural, morphological, and electrocatalytic performance of Vx-Co1-x-P composites was also investigated in-depth. Impressively, the optimized amorphous V0.1-Co0.9-P nano-electrocatalyst exhibits outstanding catalytic activity with a low overpotential of 50 mV at a current density of 10 mA cm-2 and a small Tafel value of 48.5 mV dec-1 in alkaline media. The results showed that V dopants in the composite change its crystal structure from the crystalline phase to the amorphous phase, resulting in the introduction of V-O sites, which regulate the electron density of the active sites and the exposure of surface active sites and thus promote the electrocatalytic HER process. This work provides a novel idea for the fabrication of high-efficiency metal phosphide based electrocatalysts.

Stabilization of Ru NPs over 3D LaCrO3 Nanostructures for High-Performance HER Catalysts in Acidic Media.

Hydrogen is considered as one of the best alternatives to carbon-based fossil fuels as energy sources. Electrocatalytic water splitting is one of the finest and eco-friendly methods for the production of hydrogen as compared to all other methods such as stream reforming carbon, hydrolysis of metal hydrides, etc. However, the sluggish kinetics on both the half-cell reactions limits the large-scale production of hydrogen. Hence, to overcome such kind of kinetic issues, designing a catalyst with characteristics of low overpotential and high stability is a matter of prime importance for the research community. Perovskite oxides are one of the well-documented materials for their excellent electrocatalytic water oxidation activity. But because of the lack of a proper proton adsorption site, these materials are unable to show proper hydrogen evolution reaction (HER) activity. Several strategies have been adopted for improving the HER activity of perovskite materials like cation doping, nanostructuring, etc. Here in this work, we prepared a shape-selective LaCrO3 (LCO) material. To enhance the electrocatalytic activity, we decorated the LCO with Ru nanoparticles via a hydrothermal method with different concentrations of Ru (Ru@LaCrO3), coined LCOn (n = 1-2.5). The as-synthesized RLCO2.5 showed the highest HER activity by demanding a low overpotential of 150 mV, whereas bare LCO demanded a higher overpotential of 364 mV to reach the benchmark current density of 10 mA/cm2. Also, RLCO2.5 showed a very low Rct value of 15.8 Ω and followed the facile kinetics with a lower Tafel value of 101 mV/dec. It also showed excellent stability over 55 h at a current density of 10 mA/cm2 in chronoamperometry studies. Acceleration degradation studies of RLCO2.5 showed comparably good activity with a small hike in overpotential toward HER. Hence, RLCO-based materials are highly helpful to develop efficient electrocatalysts to produce hydrogen in a large scale.

Bio‐inspired NiO/ZrO2 mixed oxides (NZMO) for oxygen evolution reactions: from facile synthesis to electrochemical analysis

AbstractBackgroundEarth's abundant natural materials can be exploited for their potential in producing economically viable and sustainable electrocatalysts for clean energy generation. Herein, we employed a low cost and environmentally benign synthesis approach using plant extract as capping agent to synthesize bimetallic NiO/ZrO2 (nickel/Zirconiu mixed oxides; NZMO), and then studied their electrocatalytic properties.ResultsThe synthesized material was characterized for its elemental, compositional and morphological feature elucidation. The phytocapping agents were probed by Fourier transform infrared spectroscopy (FTIR) and gas chromatography–mass spectroscopy (GC–MS) which confirmed the active contribution of phytocompounds in synthesis as capping and stabilizing agents. Elemental and X‐ray photoelectron spectroscopic (XPS) analysis manifested the presence of Ni, Zr and O content with morphological elucidations representing well‐defined structures. The synthesized material was systematically investigated for electrocatalytic performance towards an oxygen evolution reaction (OER). Electrochemical testing showed that the NZMO exhibits remarkable enhanced catalytic activity with 0.39 V overpotential value and 72 mV dec−1 Tafel value at an existing density of 10 mA cm−2, which is comparable to that of precious metal catalysts.ConclusionExperimental investigation demonstrates that the remarkable OER performance of NZMO could be attributed to intrinsic catalytic properties originating as a result of binary materials. Moreover, the organic compounds involved in the synthesis mechanism also could be the major contributors in terms of provision of active sites due to protons. Thus, the present work presents a promising electrocatalytic material using mixed metal oxides and paves a novel path toward the green synthesis of binary oxides with improved electrocatalytic performance. © 2022 Society of Chemical Industry (SCI).

Promising water splitting applications of synergistically assembled robust orthorhombic CoSe2 and 2D Ti3C2Tx MXene hybrid

In prospect to the unrelenting energy demand, the hunt for clean,green, sustainable and renewable energy sources has been the focal research area in the fast few decades. Hydrogen energy can be an impeccable substitute for non-renewable fossil fuels and the concern of energy crunch can be circumvented. The production of oxygen and hydrogen from water electrolysis (otherwise known as hydrogen evolution reaction-HER and oxygen evolution reaction-OER, the half-cell reactions) is one of the most clean and green energy productions. Cost-effective, noble metal free, efficient and robust electrocatalysts are needed to address the aforementioned stumbling. Herein, we have synergistically designed a robust-interface involving orthorhombic CoSe2 nanorods and two dimensional Ti3C2Tx MXene sheets for promising overall water splitting application. The above-mentioned catalyst was characterized comprehensively through XRD, FESEM, EDAX, HRTEM, XPS and BET surface area analysis. In terms of electrocatalytic activity, the catalyst performance was incredible in both HER and OER. The amalgamated catalyst exhibited a rapid charge transfer kinetic metrics and attained an overpotential of 230 mV and 65 mV/dec of Tafel value for effectual HER application whereas for OER, the catalyst revealed 270 mV of overpotential and 71 mV/dec of Tafel slope at 10 mA/cm2. In both cases the catalyst withstands a long-term stability test for more than 12 h and the after-stability polarization curves just matched with the before stability LSV curves conveying the idea of the robustness of the material. We hope this catalyst can be turned out to be a frontier in the field of energy conversion owing to its better charge transfer characteristics, lager surface area, ample electrochemical active sites and high hydrogen binding along with high dissociations which can be ascribed to the synergistic effect.

Electrocatalytic hydrogenation of nitrogenous heterocyclics using Co-based nanoparticles-embedded N-doped carbon derived from ZIF-67

Electrocatalytic hydrogenation (ECH) has been used as a novel approach for the synthesis of organic compounds. Hence, ZIF-67 was selected as a precursor in this study to synthesize a series of electrodes. The ECH effects were assessed on pyridine and diazines. The results showed a significant influence of carbonization temperature and time on the electrocatalyst activity. A temperature of 400 °C was found not high enough for the synthesis of the electrocatalysts, and a long time of 4 h at 800 °C resulted in damage to the spatial structure of the electrocatalyst. The optimal electrocatalyst was obtained under 800 °C and 2 h (Co/NC-800–2). The polyhedral Co/NC-800–2 (20–200 nm) had the N-doped graphitic-carbon shell with embedded Co/CoN/Co 3 O 4 nanoparticles. The onset potential and overpotential (at 10 mA cm −2 ) were estimated to respectively 64 and 155 mV versus hydrogen evolution reaction (HER), with a Tafel value of 62 mV dec −1 . The ECH on pyridine and diazines revealed a positive correlation between ECH effect and HER activity. Co/NC-800–2 possessed excellent ECH activity toward pyridine and pyrazine at − 0.3 V (vs. RHE). N–Co, pyridinic-N, and graphitic-N acted as active sites during electrocatalysis. The N-doped graphitic-carbon promoted the charge transfer during ECH processes. • The carbonation conditions significantly affected ZIF-67-derived electrodes activity. • The optimal HER activity electrocatalyst was obtained at 800 °C and 2 h. • The hydrogenation behavior of electrode for pyridine was similar to the HER activity. • Co/NC-800–2 showed admirable electrocatalytic hydrogenation of pyridine and diazines. • The efficient catalytic mechanism of Co/NC-800–2 was proposed.

Growth of ultrathin nanosheets of nickel iron layered double hydroxide for the oxygen evolution reaction

Because of low cost and abundance, nickel-iron double layered hydroxide (NiFe LDH) is seen as a viable substitute for noble-metal-based electrodes for the oxygen evolution reaction (OER). Herein, we report the growth of NiFe LDH in the form of fine nanosheets in a single step using benzyl alcohol-mediated chemistry. The electrochemical studies clearly suggest that benzyl alcohol is capable of inducing effective chemical interaction between Ni and Fe in the NiFe LDH. The overpotential to produce benchmark 10 mA cm −2 ( η 10 ) for the NiFe LDH electrode is only ∼270 mV RHE , which is much smaller than those of benchmark IrO 2 ( η 10 = 318 mV RHE ), nickel hydroxide ( η 10 = 370 mV RHE ) and iron hydroxide ( η 10 = 410 mV RHE ) for the OER. The difference of the overpotential requirement increases further with increasing current density, indicating faster kinetics of the OER at the catalytic interface of the NiFe LDH. Estimation of Tafel values verifies this notion – the Tafel slopes of NiFe LDH, Ni(OH) 2 , and FeOOH are calculated to be 48.6, 55.8, and 59.3 mV dec −1 , respectively. At η = 270 mV, the turnover frequency (TOF) of the NiFe LDH is 0.48 s −1 , which is ∼8 and ∼11 folds higher than those of Ni(OH) 2 (0.059 s −1 ) and FeOOH (0.042 s −1 ). In addition to Tafel and TOF, the NiFe LDH electrode has favorable electrochemically active surface area and electrochemical impedance. The electrochemical stability of the NiFe LDH electrode is assessed by conducting potentiostatic measurements at η = 270 mV RHE (∼10 mA cm −2 ) and at η = 355 mV RHE (∼30 mA cm −2 ) for 24 h of continuous oxygen production. • Growth of highly uniform and thin nanosheets of NiFe LDH in benzyl alcohol solvent. • The NiFe LDH exhibits much higher OER activity than those of Ni(OH) 2 and FeOOH. • The NiFe LDH exhibits better OER activity than the benchmark IrO 2 . • The activity of the NiFe LDH is correlated to Tafel slope, ECSA, EIS, charge transfer. • The TOF of the NiFe LDH was ∼8 and ∼11 folds higher than those of Ni(OH) 2 and FeOOH.

High-performance CoNb phosphide water splitting electrocatalyst on plasma-defect-engineered carbon cloth

Drum-shaped CoP 3 -Nb 2 P water splitting electrocatalyst is synthesized in situ on plasma-defect engineered carbon cloth. Excellent electrocatalytic stability and activity are achieved, highlighted by the low overpotentials to generate j 10 , j 500 and j 1000 of 111, 317 and 375 mV, respectively, as well as over 50h stable operation. • Plasma defect engineering enhances electrocatalyst binding with flexible carbon support. • Plasma-modified carbon cloth supports drum-like Co-Nb phosphide catalyst. • Granular Co-Nb phosphide structure with huge electrochemically active area. • Superior electrocatalytic performance achieved with high current density. • In-situ Raman and DFT results confirm synergistic effect between Co and Nb phosphide. Herein, an efficient and stable Co-Nb bimetallic phosphide electrocatalyst for HER is successfully engineered on the dielectric barrier discharge (DBD) plasma modified carbon cloth (PCC) at ambient conditions. The resulting microsized drum-like CoP 3 -Nb 2 P catalysts supported by the PCC show high electrocatalytic activity, which only needs overpotentials of 111, 317 and 375 mV to generate current densities of 10, 500 and 1000 mA cm −2 ( j 10 , j 500 and j 1000 ) respectively. A small Tafel value of 72.8 mV dec −1 is achieved. When the current density is over j 202 , the performance of the CoP 3 -Nb 2 P/PCC surpasses commercial noble metal-based Pt/C/PCC catalysts. The current density drops only 6.4 % after 50 h I-t testing at j 100 , indicating a good electrochemical stability. Theory calculations and in-situ Raman spectra results reveal the synergistic effect between Co and Nb phosphide causes a remarkable HER performance, and the Nb-Nb vibration weakens the P-H ads bond, leading to the effective H 2 generation.

Insertion of carbon skeleton in Ni/MoO2 heterojunction with porous hollow sphere for efficient alkaline electrochemical hydrogen production

The catalyst morphology has a strong impact on the activity of electrocatalytic hydrogen production. Considering the effect, we design and fabricate hollow spherical Ni/MoO2 heterojunction. In addition, an amorphous carbon skeleton is inserted into the hollow sphere, which makes the structure more stable and porous. Compared with other morphological Ni/MoO2, the porous hollow spherical Ni/MoO2 (H-Ni/MoO2) with an internal carbon skeleton shows better hydrogen evolution reaction (HER) activity with a small overpotential of 58mV to reach 10mAcm-2 and a tafel value of 44.8mV dec-1 in alkaline media. The developed HER performance of H-Ni/MoO2 can be attributed to the larger active surface area of porous hollow spherical structure and the faster electron transfer and better stability of carbon skeleton. Undoubtedly, the urea plays a crucial role to construct the hollow spherical morphology and being decomposed to form holes and amorphous carbon in the synthesized steps. The soft-template strategy using urea as the addition for forming the porous hollow structure with carbon skeleton can be extended to explore superior non-noble metal for hydrogen production.

Spectroscopy and Cyclic Voltammetry Properties of SPEEK/CuO Nanocomposite at Screen-Printed Gold Electrodes.

A successful electrochemical study of copper oxide nanoparticles (CuO NPs), sulfonated poly (ether ether ketone) polymer (SPEEK), and sulfonated polyether ether ketone-copper oxide (SPEEK/CuO) nanocomposite on bare gold electrodes was conducted. The synthesized CuO NPs and SPEEK/CuO nanocomposite were characterized using X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS). The XRD showed that the diameter of the CuO NPs synthesized was 20.44 nm. The cyclic voltammetry properties of bare screen-print gold, SPEEK and SPEEK/CuO-modified electrodes were assessed in a 5 mM K3[Fe(CN)6] solution. The electrochemical performance of the fabricated electrodes investigated revealed that CuO NPs improved the electrochemical properties of SPEEK, and the quantum size effect indicated good adsorption by the SPEEK/CuO nanocomposite compared to the SPEEK polymer and the CuO NPs alone. Moreover, the Tafel values indicated the enhanced electrochemical performance of the other electrodes as compared with the SPEEK/CuO nanocomposite. This, therefore, confirmed the successful incorporation of CuO NPs into the SPEEK polymer, as the increased surface area and the interactions between the polymer matrix and CuO fillers improved the electrochemical performance of the electrode.