Low Tafel Slope Research Articles

Construction of δ-FeOOH/NiMn2S4 heterointerface for efficient alkaline oxygen evolution reaction

Alkaline water electrolysis driven by sustainable energy is a viable approach for large-scale green hydrogen production. The development of non-precious metal-based electrocatalysts that combine high activity and stability for the alkaline oxygen evolution reaction (OER) is of great importance. In this work, we design and construct a δ-FeOOH/NiMn2S4/NF heterointerface using a solvothermal/calcination process followed by a facile successive ionic layer adsorption reaction (SILAR) treatment. Experimental tests indicate that the formation of the heterogeneous interface between the δ-FeOOH and the NiMn2S4 creates a good electron transport channel for an efficient electrocatalytic process and improves the charge transfer kinetics. As a result, the prepared δ-FeOOH/NiMn2S4/NF exhibits a low overpotential of 210 mV at 10 mA cm−2 and a low Tafel slope value of 46.6 mV dec−1, and satisfactory stability with a 92.9 % retention after 72 h of OER operation at around 100 mA cm−2. In situ Raman and in-situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) tests show that the introduction of δ-FeOOH inhibits the oxidation of Ni2+ to Ni3+ and stabilizes the Ni-S bond to prevent its auto-oxidation, leads to an increase in the electrocatalytic OER activity.

Vacancy-Activated Surface Reconstruction of Perovskite Nanofibers for Efficient Lattice Oxygen Evolution.

Inducing the surface reconstruction of perovskites to promote the oxygen evolution reaction (OER) has garnered increasing attention due to the enhanced catalytic activities caused by the self-reconstructed electroactive species. However, the high reconstruction potential, limited electrolyte penetration, and accessibility to the perovskite surface greatly hindered the formation of self-reconstructed electroactive species. Herein, trace Ce-doped La0.95Ce0.05Ni0.8Fe0.2O3-δ nanofibers (LCNF-NFs) were synthesized via electrospinning and postcalcination to boost surface reconstruction. The upshift of the O 2p band center induced by the rich oxygen vacancies lowered the reconstruction potential, and the specific one-dimensional nanostructure effectively enabled enhanced electrolyte accessibility and permeation to the LCNF-NFs. These collectively caused massive in situ generation of self-reconstructed electroactive Ni/FeO(OH) species on the surface. As a result, the surface-reconstructed LCNF-NFs exhibited accelerated lattice kinetics with a comparatively lower Tafel slope of 50.12 mV dec-1, together with an overpotential of only 342.3 mV to afford a current density of 10 mA cm-2 in 0.1 M KOH, which is superior to that of pristine LaNi0.8Fe0.2O3-δ nanoparticles (NPs) and the same stoichiometric La0.95Ce0.05Ni0.8Fe0.2O3-δ NPs, commercial IrO2, and most of the state-of-the-art OER electrocatalysts. This study provided deep insights into the surface reconstruction behaviors induced by oxygen defects and an intellectual approach for constructing electroactive species in situ on perovskites for various energy storage and conversion devices.

Orange peel derived activated carbon supported Ni–Co3O4 as an efficient electrocatalyst for oxygen evolution and reduction reaction in alkaline media

This study focuses on the development of a cost-effective electrocatalyst with excellent activity and stability for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), which is crucial for water electrolysis and fuel cell technologies. Waste orange peel is utilized as a carbon precursor to synthesize biomass-derived activated carbon (OPAC) with a unique three-dimensional sheet-like microstructure. Subsequently, a simple hydrothermal method is employed to modify the OPAC by introducing Ni-doped Co3O4, leading to the formation of a Ni–Co3O4/OPAC hybrid. We propose the Ni–Co3O4/OPAC hybrid as a highly efficient bifunctional electrocatalyst for both OER and ORR. Co3O4/OPAC and Co3O4 catalysts are also prepared for comparison. Remarkably, the Ni–Co3O4/OPAC hybrid exhibits significantly enhanced OER activity compared to Co3O4/OPAC and Co3O4 catalysts. It demonstrates a lower overpotential of 360 mV and a lower Tafel slope of 55.47 mV/dec, indicative of more efficient electrochemical performance. Moreover, in the ORR analysis, the Ni–Co3O4/OPAC hybrid displays a two-step pathway and achieves a higher ORR limiting current density compared to the Co3O4/OPAC and Co3O4 catalysts. These results highlight the synergistic effects of Ni and Co species, along with the unique properties of the OPAC support, which contribute to the enhanced activity, stability, and electron transfer characteristics of the Ni–Co3O4/OPAC hybrid. Furthermore, the improved electrical conductivity of the Ni–Co3O4/OPAC hybrid makes it a promising candidate for applications in metal-air batteries and other energy conversion devices. The utilization of waste orange peel as a carbon precursor and the facile synthesis method demonstrate the potential for cost-effective and sustainable electrocatalyst production. Overall, the Ni–Co3O4/OPAC hybrid represents a significant advancement in electrocatalyst design and holds promise for advancing the field of energy conversion and storage.

Efficient nano-size ZnM/rGO (M = Ni, Cu, and Fe) electrocatalysts for oxygen electrode reactions in alkaline media

Herein, zinc with nickel, copper, and iron was deposited on reduced graphene oxide (rGO) (ZnM/rGO, M = Cu, Ni, Fe) and examined as novel bifunctional electrocatalysts for oxygen evolution (OER) and oxygen reduction (ORR) reaction in alkaline media. Fourier-transform infrared and X-ray photoelectron spectroscopy, X-ray powder diffraction analysis, transmission, and scanning electron microscopy with energy-dispersive X-ray spectroscopy were used for the examination of structural and morphological properties of ZnM/rGO. ZnFe/rGO showed the lowest OER overpotential and Tafel slope, the highest OER current density with the lowest charge-transfer resistance. Furthermore, ORR at ZnFe/rGO proceeds by mixed 2e/4e mechanism, and by 2e mechanism at the other materials. Still, ZnCu/rGO showed the most positive onset potential and low Tafel slope during ORR. Hence, ZnFe/rGO presents the best OER activity with further improvements needed in terms of its ORR performance to reach full potential for rechargeable metal-air batteries and unitized regenerative fuel cells.

Enhancement of the urea oxidation reaction by constructing hierarchical CoFe-PBA@S/NiFe-LDH nanoboxes with strengthened built-in electric fields

The slow kinetics of the oxygen evolution reaction (OER) present a major obstacle for efficient hydrogen production via water electrolysis. In contrast, the urea oxidation reaction (UOR), with its lower thermodynamic barrier, presents a promising alternative to OER. In this study, we designed and synthesized hierarchical CoFe- PBA@S/NiFe-LDH nanoboxes. Sulfur doping in nickel–iron layered double hydroxides (S/NiFe-LDH) introduces a weak built-in electric field (BIEF), which is further strengthened when combined with cobalt-iron Prussian blue analogue (CoFe-PBA) to form a heterojunction. This heterojunction created localized charge polarization at the interface, facilitating efficient electron transfer and reducing the adsorption energy of reaction intermediates, thereby significantly improving intrinsic catalytic activity. Under conditions of 1 M KOH and 0.33 M urea, the CoFe-PBA@S/NiFe-LDH catalyst achieved a current density of 50 mA cm−2 at a relatively low potential of 1.321 V, accompanied by a low Tafel slope (53 mV dec−1). Additionally, it maintained stability at 30 mA cm−2 for 40 h. This work provides vital insights for the strategic design of highly effective heterojunction catalysts for the UOR.

Enhancing electrochemical performance of Co3O4/ZnO composite nanostructures through interface engineering for oxygen evolution reaction

Co3O4/ZnO composite nanostructures were successfully synthesized via a simple hydrothermal method followed by air-based calcination at 500°C. The resulting hexagonal heterostructure composite with a large interfacial area demonstrates exceptional oxygen evolution electrocatalytic activity with an overpotential of 288 mV at 10 mA cm-², and a low Tafel slope (80 mV dec⁻¹). This enhanced activity is attributed to the Co3O4/ZnO p-n junction, where ZnO (an n-type semiconductor) and Co3O4 (a p-type semiconductor) meet, which is crucial for boosting catalytic activity. This interface enables swift electron movement between the two materials, resulting in better charge separation and decreased charge recombination. Additionally, the high active surface area, confirmed by cyclic voltammetry measurements, further contributes to the improved OER performance. The well-defined interfaces within the Co3O4/ZnO heterostructures provide abundant active sites, facilitating efficient charge transfer kinetics. This research highlights the potential of composite heterostructures as promising electrocatalysts for water-splitting applications.

Ordered Pt3Ni intermetallic compound: A high-performance oxygen reduction reaction catalyst for Zn-air batteries

The development of advanced catalysts for oxygen reduction reaction (ORR) is crucial for Zinc-air batteries (ZABs). In this study, we focus on the controlled synthesis of ordered Pt3Ni intermetallic compounds through impregnation and high-temperature annealing, aiming to enhance the ORR performance for ZABs. The ordered Pt3Ni (denoted as Pt3Ni) and conventional alloy Pt3Ni (denoted as A-Pt3Ni) are synthesized at 600 ℃ and 200 ℃, respectively. Detailed structural characterizations confirm the formation of both ordered and disordered structures. Pt3Ni demonstrates superior ORR catalytic activity and stability compared to A-Pt3Ni and commercial Pt/C catalyst, as evidenced by higher half-wave potentials, lower Tafel slopes, and enhanced electrochemical stability. Furthermore, Pt3Ni exhibits exceptional performance in ZABs, with higher power density, specific capacity, and longer cycle life than its counterparts. These findings highlight the potential of ordered Pt3Ni intermetallic compounds as efficient ORR catalysts in ZABs, offering a promising route for the development of advanced energy conversion and storage systems.

Subnanometric Pt-W Bimetallic Clusters for Efficient Alkaline Hydrogen Evolution Electrocatalysis.

Rational design and synthesis of subnanometric bimetallic clusters (SBCs) within a narrow size distribution, along with achieving full SBCs exposure on supporting materials, are formidable challenges that must be overcome to realize potential applications. This work details a facile strategy to synthesize fully exposed PtW SBCs with an average size of 0.81 nm on the surface of spherical N-doped carbon (PtW/NC), which is underpinned by the electrostatic interactions between the negatively charged [H3PtW6O24]5- polyanions and the positively charged closed-pore metal-organic framework (MOF) [Zn5(OH)2(AmTRZ)6]2+. The PtW/NC exhibits significant electrocatalytic performance and stability for the alkaline hydrogen evolution reaction with an ultralow overpotential of 4 mV at 10 mA cm-2, a low Tafel slope of 29 mV dec-1, and a long-term electrolysis stability exceeding 140 h. The Pt mass activity of PtW/NC is 34 times higher than that of commercial 20 wt % Pt/C at the 100 mV overpotential. Both theoretical calculations and electrochemical measurements indicate that a synergistic effect between Pt and W is responsible for this notable catalytic performance. The synthetic approach outlined in this work can be applied to other MOFs and coordination networks that lack pores or have limited porosity.

FeCoNi-Based Alloy Coatings as Low Overpotential Electrocatalysts for Alkaline Water Electrolysis.

Developing efficient, stable and low-cost electrocatalysts is a viable approach to solve the current energy crisis. It is found that increasing the surface area of the electrodes can effectively promote the electrocatalytic efficiency. Herein, the atmospheric plasma spraying (APS) technology was used to prepare FeCoNi-Ni3C alloy coating by adding Ni3C powder to FeCoNi powder with an equal molar ratio. After mechanical mixing, the atomic ratios of Ni3C in the powder are 25 %, 50 %, and 75 %, respectively. The results prove that the pores on the surface of the coating have increased after Ni3C doping, which can provide more active sites in the electrocatalytic process to promote the electrocatalytic reaction. By controlling the proportion of Ni3C, the porosity of the coating surface can be effectively regulated. The results suggested that in 1.0 M KOH electrolyte and 10 mA cm-2, the FeCoNi coating shows an overpotential of 191 and 277 mV for HER and OER, respectively, the HER overpotential of 50 at % Ni3C FeCoNi-Ni3C coating is 105 mV, and the OER overpotential is 212 mV. It is worth noting that the 50 at % Ni3C FeCoNi-Ni3C coating has a low Tafel slope of 45.78 mV dec-1 (HER) and 44 mV dec-1 (OER). Meanwhile, the attenuation of the overpotential of the 50 at % Ni3C FeCoNi-Ni3C coating after the stability test is almost negligible, indicating that the prepared catalyst has excellent electrocatalytic stability. Furthermore, the 50 at.% Ni3C FeCoNi-Ni3C coating catalyst has a low potential of 1.664 V at 10 mA cm-2 in a water-splitting system. This work provids a new idea for designing inexpensive electrocatalysts.

Cation‐Modified Co‐Based Borophosphates for Efficient and Robust Oxygen Evolution Reaction

AbstractThe development of cost‐effective electrocatalysts for oxygen evolution reaction (OER) is critical and challenging in the field of electrocatalytic water splitting for industrial applications. Herein, a series of cations (Fe, Ni, and Zn)‐doped Co‐based borophosphates with an anion skeleton (Na2CoB3P2O11(OH)·nH2O are prepared by a simple hydrothermal method, in which the cation dopants could be easily achieved via a simple cation exchange during the hydrothermal reaction process. Especially, the Fe dopant increases active sites, improves charge‐mass transfer, and tunes the electronic structures of the Co‐based borophosphate electrode. The optimal Fe‐doped NaCBPO (NaC3FBPO), with the cobalt to iron molar ratio of 3, shows a low overpotential of 289 mV at the current density of 10 mA cm−2, and it can be stable for 16 h at this current density. Above all, it has a fast reaction rate with a low Tafel slope of 84.25 mV·dec−1. This work provides a promising transition metal‐based borophosphates materials with high efficiency and durability toward water splitting.

Electrochemical self-construction to fabricate NiFeCoMnSn electrocatalysts: Enhanced lattice distortion effect induced by Sn incorporation for superior hydrogen evolution performance

High-entropy alloy electrocatalysts can better regulate the electronic structure and provide opportunities for catalytic reactions to a greater extent due to the synergistic effect between its multi-metal components. In this paper, Ni-Fe-Co-Mn-Sn high-entropy alloy (NFCMS-HEA) electrocatalysts were successfully prepared by one-step electrodeposition method on nickel foam substrate. The introduction of Sn atoms, which have significantly different atomic sizes compared to other elements, results in an increased degree of lattice distortion in the HEA and a highly open multi-level nanostructured surface, thereby endowing the catalyst with exceptionally high hydrogen evolution performance. The optimized NFCMS-HEA electrocatalyst exhibits a low overpotential of 4.3 mV at a current density of 10 mA cm−2 and a low Tafel slope of 59.7 mV dec−1 in 1 M KOH solution. In addition, it maintains a superior stability of electrolysis for more than 100 h in 1 M KOH solution. In conclusion, the present study offers prospects for the preparation of HER high-entropy catalysts by one-step electrodeposition.

Fabrication of MXene-TiO2 nanotube composite and their electrochemical study in acidic and alkaline medium

MXenes, a novel class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, have emerged as promising electrocatalysts for the hydrogen evolution reaction (HER) due to their remarkable electrical conductivity, exceptional structural and chemical stability, and large active surface area. In this study, we synthesized a 1D/2D Ti3C2 MXene-TiO2 nanotube (TNT) composite via electrostatic self-assembly method. Field emission scanning electron microscopy (FE-SEM) confirmed the distinctive accordion-like, multilayered morphology of Ti3C2Tx MXene, while X-ray diffraction (XRD) provided the crystalline phase of the composite. High-resolution transmission electron microscopy (HR-TEM) revealed an average particle size of 38.41 nm for the MXene-TNT nanocomposite. Additionally, X-ray photoelectron spectroscopy (XPS) confirmed the composite composition, highlighting the synergistic integration of MXene and TiO2 nanotube that enhances electrical interactions and contributes to superior catalytic performance. Electrochemical performance was assessed using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) in both acidic and alkaline media. Among the composites, the MXene-TNT (1:10) loading demonstrated a low Tafel slope of 65 mV/dec in acidic media, indicative of enhanced mass transfer properties. In alkaline media, the MXene-TNT (1:5) composite exhibited a Tafel slope of 160 mV/dec for HER, with kinetic performance proving more favorable in the acidic environment. Additionally, the composite displayed a Tafel slope of 149 mV/dec for the oxygen evolution reaction (OER) in acidic media. This study demonstrates a feasible approach for developing high-performance, cost-effective electrocatalytic materials for efficient hydrogen production, utilizing MXene as a co-catalyst.

In-Situ Sulfuration of Ni(OH)2 to Heterostructured Ni3S2/Ni(OH)2@Ni Catalyst for Efficient Water Splitting.

The exploring and developing non-precious transition metal-based catalysts for practical water electrolysis with the low cost, high efficiency and easy macroscopic preparation was still a challenge. Herein, Ni3S2/Ni(OH)2 heterojunction with different sulfuration time was proposed and hydrothermally synthesized using a simple two-step approach, which served as a bifunctional electrocatalyst for water splitting in alkaline solution at industrial temperature. Among these catalysts, Ni3S2/Ni(OH)2-5h displayed the smallest overpotentials (237 mV@100 mA cm-2 and 360 mV@100 mA cm-2) for OER and HER at room temperature, along with low Tafel slopes of 62.0 mV dec-1 and 80.8 mV dec-1 respectively. Furthermore, working at high temperature Ni3S2/Ni(OH)2-5h exhibited even lower overpotential of 82 mV@100 mA cm-2 at 70 °C for OER and 325 mV@100 mA cm-2 at 60 °C for HER. The excellent performance was ascribed to the heterojunction accelerating the charge transfer, hierarchical interconnected structure promoting the mass transfer and the synergistic effect between the components of Ni3S2 and Ni(OH)2. This work could provide a promising route for promoting the electrocatalytic performance of Ni-based catalyst with a simple sulfuration method for industrial water splitting, which could expand to other non-noble metal-based materials for enhancing the electrocatalytic activities.

Construction of bifunctional MOF-based composite electrocatalysts promoting oxygen evolution reaction and glucose oxidation reaction and its kinetic deciphering

The climate crisis and the need for green and sustainable energy drive the rapid development of hydrogen production from water electrolysis. Improvements in the kinetics of the anode reaction, which governs the efficiency of water electrolysis, are essential for efficient hydrogen production and key to effectively addressing global environmental and energy challenges. Hence, we focus on improving the kinetics of the anode oxidation reaction. The multi-walled carbon nanotubes coupled with bimetallic organic framework (CoFe-MOF-74) composite electrocatalysts (CoFe-MOF-74@MWCNT) were fabricated for OER and the kinetically more favorable glucose oxidation reaction (GOR). Compared to commercial RuO2, CoFe-MOF-74@MWCNT showed superior OER catalytic performance, exhibiting a lower overpotential (273 mV) and a lower Tafel slope (55 mV dec−1) at a current density of 10 mA cm−2. Moreover, after adding glucose to the anode, the potential required of 10 mA cm−2 was only 1.291 V (vs. RHE), a reduction of 212 mV compared to the OER potential. This reduction in potential demonstrates the efficiency of our catalysts and signifies significant energy savings. The characterization results and theoretical calculations indicated that the superior OER/GOR performance of CoFe-MOF-74@MWCNT can be ascribed to the synergistic effect between MWCNT and the mixed metal nodes of the bimetallic organic framework. The doping of MWCNT promoted the catalyst charge transfer efficiency (Rct was only 5.56 Ω) in the OER process. The mixed metal nodes of CoFe-MOF-74@MWCNT provided more active sites for the electrocatalytic reaction, and promoted the bond-breaking of critical intermediates in the oxidation process, significantly reducing the free energy of catalytic intermediates and accelerating reaction kinetics. This work provides a strategy for designing multifunctional electrocatalysts for OER and biomass small molecule oxidation and highlights the potential for significant energy savings in practical applications.

Effective Improvement of Thermodynamics and Kinetics of BiVO4 Photoanode via CuI for Photoelectrochemical Water Oxidation.

The preparation of durable and efficient photoanodes for photoelectrochemical water oxidation is of great importance in promoting the development of green hydrogen production and artificial photosynthesis. Here, n-type BiVO4 was combined with p-type CuI to construct a CuI/BiVO4 (CIB-1) p-n heterojunction photoanode. The composite photoanode effectively overcame the drawbacks of BiVO4, such as low separation and injection efficiency of photogenerated electron-hole pairs. As a result, the CIB-1 had the highest photocurrent density of 1.98 mA cm-2, which was 2.5 times higher than pure BiVO4 with 0.79 mA cm-2 at 1.23 V (vs RHE) under AM 1.5G light irradiation. The CIB-1 had a lower Tafel slope of 23.2 mV decade-1 compared to 47.9 mV decade-1 for BiVO4, so the water oxidation kinetics was remarkably advanced over CuI/BiVO4. Based on DFT calculations, the OER overpotential of 0.480 V for CuI/BiVO4 was significantly lower than that of 1.546 V for BiVO4 due to the lower free energy from OH- to oxygen over CuI/BiVO4 compared to BiVO4.

Biomass Electrocatalysts: Exploiting Haemoglobin-derived Fe Sites Supported by Waste-derived, S and N-enriched Carbon for Efficient Oxygen Electro-reduction

Abstract Biomass resources offer a diverse array of low-cost feedstocks having interesting functional properties for the manufacture of electrocatalysts for the energy sector. In this study, haemoglobin (Hb), lignin, tannic acid and urea were used to make high surface area N, S-codoped carbon electrodes rich in highly dispersed heme-like (Fe-Nx) sites. By pyrolyzing precursor mixtures containing un-purified Hb, lignin, tannic acid and urea, in appropriate mass ratios, a high surface-area S, N-codoped carbon nanostructured electrocatalyst was obtained. The electrocatalyst had surface pyridinic and pyrrolic species together with highly dispersed N-coordinated Fe sites. The developed FeSN/C electrocatalyst exhibited an ORR onset potential of 0.98 V vs. RHE in 0.1 M KOH, a half-wave potential of 0.87 V and a low Tafel slope of 54 mV/dec. This work encourages the design of biomass-derived electrocatalysts for ORR, in particular showing that haemoglobin in bovine blood is suitable for use as an iron source when making Fe-N-C electrocatalysts.

Multifunctional benzoselenadiazole-capped organic molecule-based nanohybrid for efficient asymmetric supercapacitor and oxygen evolution reaction

Nanostructured hybrid materials have attracted significant interest in the field of energy storage and conversion. To investigate the effect of all nanohybrids on electrochemical properties, we have synthesized organic-inorganic nanohybrids through in situ galvanostatic electrodeposition using a monometallic and bimetallic composition of nickel, cobalt salts and an organic molecule. The electrochemical studies reveal that BSeFY/NCDH (20:20) (BSe = benzo[2,1,3]selenadiazole, F = L-phenylalanine and Y = L-tyrosine; NCDH = nickel‑cobalt double hydroxide) hybrid electrode performs more efficiently than 40:0, 0:40, 10:30, 30:10 and nickel‑cobalt double hydroxide-20:20 (NCDH-20:20) electrodes. The specific capacitance of the 20:20 hybrid electrode is measured to be 1338.46 F/g at 2 A/g current density. The AC/NF negative electrode was made using activated carbon, carbon black and polyvinylidene fluoride (PVDF) in a ratio of 80:15:5. The fabricated asymmetric device reveals the energy density of 35.48 Wh/kg at a power density 751.36 W/kg. Furthermore, the device exhibits a capacitance retention of 91.24 % after 5000 cycles at 7 A/g current density. This fabricated device has the ability to illuminate a red LED and operate a small fan. Furthermore, the designed and fabricated hybrid materials are highly efficient for the oxygen evolution reaction (OER). Among the fabricated materials, the 20:20 hybrid electrode is highly active and achieves a lower overpotential of 240 mV with a low Tafel slope of 62 mV/dec at a current density of 10 mA/cm2. Furthermore, the BSeFY/NCDH (20,20) hybrid is highly robust and shows negligible activity loss after 55 h of chronopotentiometry measurement at 10 mA/cm2 current density. Furthermore, multistep chronopotentiometry was performed in the current density range of 4 to 40 mA/cm2 and the results exhibit that the potential rapidly levels off in the next 400 s due to the robust electrochemical stability, rapid mass and electron transportation ability of 20:20 nanohybrid. Therefore, the electrochemical investigations demonstrate that the bimetallic organic-inorganic nanohybrid is highly active in supercapacitor and OER due to its abundant electrochemical active sites, high conductivity, enhanced Faradaic redox properties, multiple valence transitions and the easy synergistic effect between metal ions and organic moiety.

Microwave-Assisted synthesis of CuxFe100-x/Carbon aerogel (x = 0, 30, 50, 70) with enhanced Electrocatalytic activity towards oxygen evolution reaction

A simple and efficient microwave-assisted synthesis route was adopted for carbon aerogel (CA)-supported Cu and Fe catalysts for OER in alkaline media. Catalysts were characterized physically by ICP-MS, XRD, TEM, XPS, SEM, and EDX and electrochemically by CV, chronoamperometry, and EIS. The catalyst having the composition of Cu30Fe70/CA showed excellent activity towards OER with low overpotential (345 mV) and Tafel slope (92.5 mV dec−1). Diffusion coefficient (D° = 2.1 × 10−8 cm2 s−1), mass transport coefficient (mT = 2.8 × 10−4 cm s−1), heterogeneous rate constant (k° = 5.7 × 10−4 cm s−1), and electrochemically active surface area (0.0167 cm2) were obtained for Cu30Fe70/CA modified glassy carbon electrode. CV response in the non-faradic region showed that Cdl and electrochemical surface area (ECSA) of Cu30Fe70/CA increased ∼ 34 times compared to Fe/CA. This work suggests that adding up an optimum amount of Cu to the Fe/CA nanocomposite offers a cost-effective and efficient electrocatalyst for OER.

Controlled synthesis of Mn\\M-doped NiP3/Cu3P (M=Cr, Ce, Bi and Co) as electrocatalysts for urea splitting reactions in alkaline solutions

Urea is generally used in agricultural fertilization to provide nutrients they need with the crops, however overuse of urea for fertilization can pollute the environment. Electrolysis urea is a greener way of treating urea, and in recent years electrolysis urea has been studied as a hot topic. It is mainly due to the fact that the potential of urea electrolysis is 0.37 V, which is smaller than the potential of traditional water splitting of 1.23 V. In this paper, a series of synthetic experiments were carried out by doping with the same content of Cr, Ce, Bi and Co into Mn-NiP3/Cu3P. It is found that Cr-doped Mn-NiP3/Cu3P possesses excellent electrochemical properties compared to nickel foam doped with the other three elements. At an iR compensation value of 70 %, Mn\\Cr-doped NiP3/Cu3P has strong catalytic activity and durability for urea oxidation reaction (UOR). At an ultra-low voltage of 1.352 V, the Mn\\Cr-doped NiP3/Cu3P catalyst had a catalytic current of 10 mA cm−2, a low Tafel slope (102.03 mV dec−1), a high Cdl (9.35 mF cm−2), and catalytic stability of more than 50 hours. The enhanced activity of Mn\\Cr-doped NiP3/Cu3P is attributed to rapid charge transfer, improved electrical conductivity, and increased electrochemical area. Density Functional Theory (DFT) calculations showed that synergic catalytic effect of Mn-Cr-NiP3 and Mn-Cr-Cu3P in the catalysts can effectively improve the adsorption capacity of the catalysts, this provides a new ideas of exploration for the electrolysis of urea with cheap and relatively low toxicity catalysts, which can effectively reduce the cost.

Fluorine-Induced Lattice Oxygen Participation in 2D Layered Double Hydroxide/MXene Hybrids for Efficient Oxygen Evolution.

In oxygen evolution reaction (OER), the participation of lattice oxygen can break the limitation of adsorption evolution mechanism, but the activation of lattice oxygen remains a critical challenge. Herein, a surface fluorinated highly active 2D/2D FeNi layered double hydroxide/MXene (F-LDH/MX) is demonstrated, boosting OER with the enhanced lattice-oxygen-mediated path. The introduction of fluorine promotes the self-evolution of catalyst in an alkaline environment, even without an external current. It further accelerates the formation of active metal oxyhydroxides with abundant oxygen vacancies under the operating potential. The introduced oxygen vacancy activates the lattice oxygen, increasing the proportion of lattice oxygen mechanism in OER. Owing to the synergistic effects of the 2D/2D hierarchical structure and the modulated active surface, F-LDH/MX possesses excellent electrochemical performances, including a low overpotential of 251 mV at 10 mA cm-2, a low Tafel slope of 40.28 mV dec-1, and robust stability. The water electrolyzer system with F-LDH/MX as the anode offers the benchmark current density at a low cell voltage of 1.53 V, while the Zn-air battery with F-LDH/MX as the air electrode exhibits a higher power density of 75.43 mW cm-2. This study presents a promising strategy to design highly active electrocatalysts for energy conversion and storage.