Half-wave Potential Research Articles

High-Entropy Nitrides as Superior Electrocatalysts: Unveiling the Role of Entropy in Enhanced Performance.

High-entropy nitrides (HENs) are emerging as promising electrocatalysts due to their diverse elemental composition, tunable electrochemical properties, and a wide range of active sites that enhance adsorption and oxidation reactions. However, the unclear role of entropy has limited their full potential in electrocatalysis. In this study, we introduce a novel and straightforward method for synthesizing (CoNiCuVW)N with variable entropy levels using halite as a molten salt. By exploiting the synergistic effects of multiple metal components, we achieve robust bonding between the N-doped carbon substrate and HEN nanoparticles, resulting in a homogeneous elements distribution. This uniformity leads to exceptional catalytic performance for the oxygen reduction reaction (ORR) in alkaline electrolytes, with an onset potential of 0.96 V and a half-wave potential of 0.91 V. Additionally, HEN-based zinc-air batteries exhibit impressive performance, achieving 1.55 V and maintaining 60% roundtrip efficiency over approximately 400 cycles. Density functional theory (DFT) calculations suggest that the high-entropy, homogeneous distribution of elements enhances active site availability, modulates electronic structure, and optimizes kinetics, thereby lowering reaction barriers during the ORR. This work not only facilitates the development of structurally ordered HEN nanoparticles but also lays the foundation for further exploration in electrochemical applications.

Hot Injection Assisted Electronically Modulated Twin and Grain Boundary Rich Sub-2 nm Pt3Co Alloy Resistant to Phosphate Ion for PEMFCs.

Modulation of the electronic d-band center, structural defects (line defects), and particle size of Pt3Co alloy electrocatalyst have huge significance in elevating its electrochemical oxygen reduction reaction activity. Deviating from traditional high-temperature strategies, the current work focuses on ripening these benefits by implying a simple economically viable hot-injection-assisted modified polyol process. A conclusive control over decrementing particle size starting from 2.7 to 1.3nm, an increasing degree of strain (twin boundary), and shifting of the d-band center away from the Fermi level are obtained via varying the temperature to which the solution is injected. The catalyst prepared via the injection at 200 °C (Pt3Co(1.3 t,g-b)/fVC-200) has delivered an electrochemical surface area of 84 m2 with the onset and half-wave potentials of 0.980 and 0.858V, respectively, versus RHE and a limiting current of -6.0mA cm-2 with stability till 20k cycles. In the high-temperature proton exchange membrane fuel cell Pt3Co(1.3 t,g-b)/fVC-200-based cell has outperformed Pt/C rendering 600 mWcm-2 under H2-Air compared to 529 mWcm-2 of Pt/C with 20% lower Pt loading and double the stability due to enhanced resistance toward phosphoric acid for accelerated voltage cycling. A similar enhancement is seen while employing the catalyst for low-temperature fuel cells.

Achieving pH-universal oxygen electrolysis via synergistic density and coordination tuning over biomass-derived Fe single-atom catalyst

Renewable biomass serves as a cost-effective source of carbon matrix to carry single-atom catalysts (SACs). However, the natural abundant oxygen in these materials hinders the sufficient dispersion of element with high oxygen affinity such iron (Fe). The lowered-density and oxidized SACs greatly limits their catalytic applications. Here we develop a facile continuous activation (CA) approach for synthesizing robust biomass-derived Fe-SACs. Comparing to the traditional pyrolysis method, the CA approach significantly increases the Fe loading density from 1.13 atoms nm−2 to 4.70 atoms nm−2. Simultaneously, the CA approach induces a distinct coordination tuning from dominated Fe-O to Fe-N moieties. We observe a pH-universal oxygen reduction reaction (ORR) performance over the CA-derived Fe-SACs with a half-wave potential of 0.93 V and 0.78 V vs. RHE in alkaline and acidic electrolyte, respectively. Density functional theory calculations further reveal that the increased Fe-N coordination effectively reduces the energy barriers for the ORR, thus enhancing the catalytic activity. The Fe-SACs-based zinc-air batteries show a specific capacity of 792 mA·h·gZn−1 and ultra-long life span of over 650 h at 5 mA cm−2.

Modulating the Cavity Size of Carbon Nanobelts for Enhanced Oxygen Reduction Reaction.

The preactivation of reactants within the cavities of carbon nanotubular materials has remained largely unexplored due to the scarcity of materials with well-defined sizes and precisely engineered doping sites. Herein, we demonstrate that the catalytic activity toward the oxygen reduction reaction (ORR) is primarily governed by the cavity sizes of well-defined nanobelt materials with precisely doped sp2-nitrogen atoms. Our results show that the confinement effect induced by cavity size and the electron-rich chemical environment within the cavity are crucial for O2 adsorption and preactivation, leading to enhanced catalytic activity. Belt2, with its medium-sized cavity (6.3 Å), exhibits superior ORR catalytic performance compared to Belt1 with its narrower cavity and Belt3/Belt4 with its larger cavities. Notably, Belt2 achieves high half-wave and onset potentials of 0.84 and 0.97 V, respectively, along with an open-circuit voltage of 1.32 V and a peak power density of 181 mW cm-2 in a zinc-air battery. This work not only provides a deeper understanding of the geometric factors influencing the ORR electrocatalysis of nanocarbon materials but also offers insights into the future design of nanocarbon electrocatalysts for enhancing catalytic efficiency. These findings may also be beneficial for other energy conversion and catalytic materials.

Engineering Proton-Coupled Electron Transfer to Break Activity-Stability Trade-Off of Oxygen Electroreduction Catalysts for Temperature-Adaptive Zn-Air Battery.

Single-atom catalysts (SACs) are regarded as effective electrocatalysts for oxygen reduction reaction (ORR). However, integrating high active and long-term durability on SACs is still challenging due to the severe limitations of the activity-stability trade-off. Herein, we report an integrative electrocatalyst combining isolated Fe sites and MoC nanoparticles (MoC/Fe─NC). MoC nanoparticles accelerate ORR kinetics via the proton-feeding effect and optimize Fe site microstructure. Thus, MoC/Fe─NC exhibits a high alkaline ORR activity with half-wave potential (E1/2) of 0.916V versus the reversible hydrogen electrode, and exceptional durability of 50k cycles with 5mV E1/2 loss. The observed ORR performance is further verified in a zinc-air battery (ZAB) with a high peak power density of 316mW cm-2 and operational stability over 1000h. Moreover, the fabricated temperature-adaptive quasi-solid-state ZAB can cycle stably for 150h under alternating temperatures. Theoretical calculations and experiment characterizations, involving scanning electrochemical microscopy techniques and distribution of relaxation times analysis, reveal that the excellent capabilities of MoC/Fe─NC arise from accelerated proton-coupled electron transfer, weakened *OH adsorption, and strengthened Fe─N bonds fueled by MoC nanoparticles. This work sheds light on breaking the activity-stability trade-off barrier of SACs for energy-conversion applications.

Trimodal Hierarchical Porous Carbon Nanoplates with Edge Curvature for Faster Mass Transfer and Enhanced Oxygen Reduction.

Although hierarchical porous carbon materials have been widely used for electrocatalysis, the role of curvature in carbon nanostructures during electrochemical reactions remains poorly understood due to a lack of experimental models featuring clearly defined curved geometries and periodic structures. In this study, we fabricate hierarchical porous cobalt- and nitrogen-containing carbon nanoplates with trimodal porosity (macro-, meso-, and micropores) and continuous, homogeneous curved edges (Co/N-CNP-CURV) using a polystyrene-directed templating approach. The Co/N-CNP-CURV catalyst exhibits excellent catalytic activity and stability for the alkaline oxygen reduction reaction, with a half-wave potential of 0.82 V and a minimal potential shift of 8 mV after 5000 cycles. The enhanced electrocatalytic activity is attributed to synergistic combinations of the trimodal porosity, abundant Co-Nx active sites, a high density of curved edges, and graphitic carbon encapsulated with cobalt nanoparticles. Density functional theory calculations reveal that the presence of curvature in Co/N-CNP-CURV is beneficial for enhancing the charge transfer from the catalyst to O2, lowering the adsorption energy of O2, and reducing the activation free energy barrier for the rate-determining step (*O2 + (H+ + e-) → *OOH). The study provides compelling experimental evidence supporting the critical role of the curvature effect in enhancing the electrocatalytic performance of nanoporous metal-containing carbon materials.

Electron Donor-Acceptor Activated Anti-Fenton Property for the Ultradurable Oxygen Reduction Reaction.

Iron-nitrogen-carbon (Fe-N-C) materials are recognized as an effective category of catalysts that do not contain platinum (Pt) for the oxygen reduction reaction (ORR). Nonetheless, the long-term stability and effectiveness of these materials are significantly hindered by the dissolution and oxidation of Fe atoms. Microstructural engineering of Fe-N-C is a viable approach to enhancing ORR activity and stability. Herein, CuN5-single-atom nanozymes (SAzyme)-assisted Fe-N5 catalysts (SA-Fe-N5) were developed by introducing single-atom Cu to enhance Fe-N-C catalyst ORR performance. Electrochemical assessments indicated that SA-Fe-N5 exhibited excellent ORR activity in alkaline solutions, with a half-wave potential and a diffusion-limited current density similar to that of commercial Pt/C. Calculations based on density functional theory indicated that a single copper atom can function as an electron donor, enhancing the electron density at the iron sites. This modification improves the adsorption and desorption energies for intermediates involved in the ORR process, ultimately boosting the ORR performance of the single-atom Fe-N5 catalyst. Moreover, the introduction of the Cu site can be regarded as a catalase single-atom nanozyme (CAT-SAzyme), facilitating the decomposition of the byproduct H2O2 to H2O and thereby enhancing the anti-Fenton activity during the ORR process. Notably, as a cathode catalyst in a zinc-air battery, SA-Fe-N5 demonstrated an impressive power density of 217.8 mW cm-2 alongside a current density of 257.3 mA cm-2.

Integrating Electronic-Storage Piperazine into Covalent Organic Frameworks for Promoting Oxygen Reduction Reaction.

Metal-free covalent organic frameworks (COFs) have emerged as potential electrocatalysts for oxygen reduction reaction (ORR) in new environmental-friendly electrochemical energy conversion technologies. However, their catalytic activity is hindered by inefficient electron transfer from electrodes to catalytic sites along extended frameworks. To overcome this bottleneck, herein, we first incorporated redox-active piperazine units into the COFs to catalyze ORR. The redox-active piperazine units enable to storage electrons, and thus accelerate the electron transferring to the catalytic sites. Furthermore, the introduction of -OH group-containing building blocks induces keto-enol tautomerism (enabling reversible -OH / -C=O interconversion), improving framework polarity with a dipole moment of 6.87 Debye (5.8 times increase compared to non-hydroxylated COFs). This polarity enhancement strengthens the intermediates binding ability, thereby improving the catalytic activity. As a result, the optimized PD-COF-OH exhibits a high half-wave potential of 0.76 V, turnover frequency (TOF) of 0.045 s-1, and electrochemically active surface area of 9.4 mF cm-2, surpassing most reported metal-free COFs. Theoretical calculations further reveal synergistic roles of -OH and -C=O groups in stabilizing OOH* and OH* intermediates, contributing to the improved catalytic activity. This work establishes a novel design paradigm for catalytic COFs through rational integration of electron reservoir units and tautomerism-enabled polarity modulation.

Synergistic Catalysts with Fe Single Atoms and Fe3C Clusters for Accelerated Oxygen Adsorption Kinetics in Oxygen Reduction Reaction.

The design of cost-effective and efficient catalysts based on transition metal-based electrocatalysts for the oxygen reduction reaction (ORR) is crucial yet challenging for energy-conversion devices like metal-air batteries. In this work, we present a cost-effective strategy for preparing catalysts consisting of single-atomic Fe sites and Fe3C clusters encapsulated in nitrogen-doped carbon layers (FeSA-Fe3C/NC). The FeSA-Fe3C/NC electrocatalyst demonstrates outstanding ORR performance in alkaline electrolytes, achieving a high half-wave potential (E1/2=0.902V), 4e- ORR selectivity, and robust methanol tolerance. The exceptional ORR catalytic performance is credited to the relatively substantial specific surface area and the optimal arrangement of active sites, including atomically dispersed Fe-N sites and synergistic Fe3C clusters. In situ spectroelectrochemical characterization and theoretical calculations verify that Fe3C clusters disrupt the symmetric electronic structure of Fe-N4, optimizing 3d orbitals of Fe centers, thereby accelerating O─O bond cleavage in *OOH to boost ORR activity. Furthermore, a zinc-air battery constructed with FeSA-Fe3C/NC demonstrates excellent potential in energy storage application, yielding a maximum power density of 151.3mW cm-2 and robust cycling durability surpassing that of commercial Pt/C catalysts. This study establishes a cost-effective route for producing metal-based carbon electrocatalysts with exceptional performance using environmentally friendly raw materials.

Multifunctional High-Entropy Alloys and Oxides for Self-Powered Electrocatalytic Nitrate Reduction to Ammonia.

High-entropy alloys (HEAs) show high activities toward oxygen reduction reaction (ORR), Zn-air batteries (ZABs) and nitrate reduction reaction (NO3 -RR). In this work, FeNiCoMnRh HEA supported by N-doped carbon frameworks is prepared and showed excellent ORR performance with a half-wave potential (E1/2) of 0.89V versus RHE, limiting diffusion current (jL) of 5.6mA cm-2 and better current stability. The HEA-assembled ZAB exhibited a high-power density of 103.8mW cm-2 with a specific capacity of 790 mAh gZn -1. Also, its oxides presented 77% Faraday efficiency (FE) for ammonia production at -0.3V versus RHE. Accordingly, our designed ZAB was employed to drive NO3 -RR to construct a self-powered system, which provides an attractive route for low-energy sewage treatment and environmentally friendly preparation of ammonia.

NaCl-Assisted electrospinning of bifunctional carbon fibers for High-Performance flexible zinc-air batteries.

NaCl-Assisted electrospinning of bifunctional carbon fibers for High-Performance flexible zinc-air batteries.

Constructing Stable Bifunctional Electrocatalyst of Co─Co2Nb5O14 with Reversible Interface Reconstitution Ability for Sustainable Zn-Air Batteries.

Transition metal and metal oxide heterojunctions have been widely studied as bifunctional oxygen reduction/evolution reaction (ORR/OER) electrocatalysts for Zn-air batteries, but the dynamic changes of transition metal oxides and the interface during catalysis are still unclear. Here, bifunctional electrocatalyst of Co─Co2Nb5O14 is reported, containing lattice interlocked Co nanodots and Co2Nb5O14 nanorods, which construct a strong metal-support interaction (SMSI) interface. Unlike the recognition that transition metals mainly serve as ORR active sites and metal oxides as OER active sites, it is found that both ORR/OER sites originate from Co2Nb5O14, while Co acts as an electronic regulatory unit. The SMSI interface promotes dynamic electron transfer between Co/Co2Nb5O14, and the reversible active sites of Nb4+/Nb5+ realize bidirectional adsorption/migration of intermediates, thereby achieving dynamic reversible interface reconstitution. The electrocatalyst shows a high ORR half-wave potential of 0.84V, a low OER overpotential of 296.3mV, and great cycling stability over 30000 s. The ZAB shows a high capacity of 850.6mA h·gZn-1 and can stably run 2050 cycles at 10 mA·cm⁻2. Moreover, the constructed solid-state ZAB also shows leading cycling stability in comparison with the previous studies.

Enhanced Catalytic Activity of Pt Nanostructured Electrodes Deposited by Spark Ablation for Proton Exchange Membrane Fuel Cells.

Catalyst layers play a crucial role in determining the performance of proton exchange membrane fuel cells (PEMFCs). However, the deposition of catalyst layers poses challenges in PEMFC stack production due to the complexity of the fabrication steps. Herein, we present a simplified approach to synthesize Pt nanostructures via spark ablation and simultaneously deposit them onto gas diffusion layers (GDL). The in situ deposited catalyst layers on GDL serve as electrodes for membrane electrode assembly (MEA) fabrication. Moreover, the carrier gas in the spark ablation process significantly influences the nucleation and growth of the Pt nanostructures. Pt nanostructures produced in forming gas (Pt_FG, 95% nitrogen, and 5% hydrogen) exhibit dendritic morphology distinct from those obtained in pure N2 (Pt_N2). Investigating the catalytic activity of Pt synthesized in different carrier gases reveals that the Pt_FG catalyst demonstrates enhanced half-wave potential, mass activity, and durability compared to those of Pt_N2 and commercial Pt-black catalysts. Single-cell measurements evaluate the electrocatalytic activity of the ionomer-free, in situ deposited catalyst layers. The Pt_FG MEA (0.2 mgPt cm-2) achieves a power density of 1285 mW cm-2 at 70 °C, 200 kPa, approximately 1.8 and 2 times higher than Pt_N2 and Pt-black MEAs, respectively. Further reduction of the catalyst loading to 0.1 mgPt cm-2 results in the Pt_FG MEA delivering 961 mW cm-2, indicating enhanced catalytic activity and Pt utilization efficiency. This study provides insights into fabricating catalytic layers using a facile strategy, circumventing the need for catalyst synthesis, ink formation, and electrode coating techniques.

Cobalt-Doped MnFe2O4 Spinel Coupled with Nitrogen-Doped Reduced Graphene Oxide: Enhanced Oxygen Electrocatalytic Activity for Zinc-Air Batteries.

MFCO spinel anchored on N-rGO is synthesized by a two-step hydrothermal method as a bifunctional electrocatalyst. Its physicochemical properties have been characterized and tested, and it is applied to zinc-air batteries. The experimental and theoretical calculations show that the MFCO is uniformly distributed on the surface of N-rGO. When MFCO is anchored on the conducting N-rGO, a synergistic effect occurs between the Co-N bonds, which changes the arrangement of the C-N bonds from the sp2 orientation to the sp3 form. The ORR catalytic pathway of the MFCO/N-rGO electrocatalyst is dominated by 4-electron transfer, with a half-wave potential of 0.8003 V, an overpotential value of 352 mV, and a small potential difference (ΔE = 0.78 V). With a charge/discharge voltage difference of about 0.88 V, the voltage gap remains almost unchanged for a long period after 650 h, showing excellent stability. The improved catalytic performance is attributed to Co acting as an active site, and the doping of Co induces the Jahn-Teller effect, which alters the electronic structure of spinel, shifts the d-band center upward, enhances the adsorption of oxygen intermediates, and promotes the oxygen electrocatalytic reaction. This study provides a low-cost and promising bifunctional oxygen electrocatalyst for zinc-air batteries.

Static magnetic field-enhanced cathodic electrocatalysis of Fe3O4-based nitrogen-doped carbon for improving the performance of microbial fuel cells.

Static magnetic field-enhanced cathodic electrocatalysis of Fe3O4-based nitrogen-doped carbon for improving the performance of microbial fuel cells.

Co/CoO hetero-nanoparticles incorporated into lignin-derived carbon nanofibers as a self-supported bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries.

Co/CoO hetero-nanoparticles incorporated into lignin-derived carbon nanofibers as a self-supported bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries.

Spin polarization regulation of Fe-N4 by Fe3 atomic clusters for highly active oxygen reduction reaction.

Spin polarization regulation of Fe-N4 by Fe3 atomic clusters for highly active oxygen reduction reaction.

FePc coupled with FeNi/WxC embeded in leaf like multistage pore carbon as highly efficient bifunctional electrocatalyst for long life zinc-air battery

FePc coupled with FeNi/WxC embeded in leaf like multistage pore carbon as highly efficient bifunctional electrocatalyst for long life zinc-air battery

Redox potentials of sulfonamide antibiotics mediating the electron transfer process in single-atom Cu catalyst/peroxymonosulfate system: Selective removal mechanisms for sulfonamides.

Redox potentials of sulfonamide antibiotics mediating the electron transfer process in single-atom Cu catalyst/peroxymonosulfate system: Selective removal mechanisms for sulfonamides.

Interface engineering of supported palladium electrocatalyst with covalent organic polymer towards oxygen reduction reaction

Interface engineering of supported palladium electrocatalyst with covalent organic polymer towards oxygen reduction reaction