Tafel Slope Research Articles

Boosted Electrochemical Hydrogen Evolution Activity via the Core-Shell Heterostructure of Nickel Sulfide Nanoframe-Supported Layered Rhenium Disulfide.

The strategic design of a heterostructure catalyst with a core-shell nanoarchitecture is imperative for enhancing the efficiency of the electrocatalytic hydrogen evolution reaction (HER). Herein, the core-shell catalyst comprising the rhenium disulfide nanosheets was vertically integrated onto a hollow nickel sulfide (NiS@ReS2) via coprecipitation and hydrothermal treatment. The morphology involves the sulfurization of a nickel-based Prussian blue analogue, effectively mitigating the aggregation of ReS2 nanosheets and maximizing the exposed active sites. By the synergistic effect of morphological design and heterostructure formation, the overpotential of NiS@ReS2 is 136 mV at 10 mA cm-2 in an alkaline electrolyte, and the rapid kinetics is confirmed by the small Tafel slope and low charge transfer resistance during the HER process. Moreover, the electrocatalytic durability of NiS@ReS2 is elucidated, and the boosted catalytic activity of NiS@ReS2 is confirmed by density functional theory. This study unveils a promising method for advancing ReS2-based electrocatalysts with potential implications for producing hydrogen.

Ni-doped CoFeP as high-efficeint electrocatalysts for water-splitting

Electrochemical water-splitting is emerging as a promising pathway to produce green hydrogen. However, the sluggish kinetics of OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) are challenging, so it is necessary to develop high-efficient and low-cost electrocatalysts. Here a few new high-efficient water-splitting catalysts of CoFeNiP-n (n refers the concentrate of Ni2+ in electrolyte) are synthesized on nickel foam by a one-step electrodeposition. CoFeNiP/NF-0.03 and CoFeNiP/NF-0.1 show the best performance of the OER and HER, respectively, which both overpotentials are 252.6 and 75.6 mV at 10 mA/cm2 in 1.0 M KOH, and both Tafel slopes are 35 and 63 mV dec‑1, respectively. When both serve as anode and cathode for overall water-splitting, respectively, a current density of 100 mA cm-2 is obtained at low cell voltages of 1.675 V in 1.0 M KOH at room temperature (RM), 1.66 V in 1.0 M KOH+3 % NaCl at RM, and 1.53 V in 1.0 M KOH+3 % NaCl at 80 °C. Simultaneously, the catalysts manifest exceptional durability for 100 h and stability after 1000 cyclic voltammetry scans. Density functional theory calculations show that Ni is the main active center of the OER, whereas Ni, Co and P become the main active center of the HER.

Metal Organic Frameworks‐Derived NiO/NiCo2O4 Heterostructures for Effective Methanol Oxidation Reaction

AbstractThe electrochemical process of methanol oxidation reaction (MOR), which is closely associated with electrochemical production of formate and hydrogen, is considered a highly viable avenue for advancing renewable energy technologies. Nevertheless, the development and creation of affordable, effective, and durable electrocatalysts for MOR continue to present significant obstacles. In this study, a hierarchical porous NiO/NiCo2O4/NF electrode is fabricated through the integration of solvothermal and thermal oxidation treatments of Ni‐MOF‐74 and NiCo‐Asp. After thoroughly assessing the electrochemical performance for MOR, NiO/NiCo2O4/NF demonstrates a significant current density of 140 mA cm−2 at 1.6 V (vs. RHE) and a tafel slop of 45.0 mV·dec−1 in 1 M KOH and 0.5 M methanol. The excellent performance of MOR can be ascribed to the hierarchical porous nature that enhances mass and electron transport while offering numerous active sites for electrocatalytic reactions. Additionally, the hetero interface between NiO and NiCo2O4 could further enhance electron transfer rate and reaction kinetics for the MOR. The developed NiO/NiCo2O4/NF electrode shows potential as a viable and economical alternative to Pt‐based electrocatalysts for MOR‐based applications.

Ultra-Fast Synthesis of Highly Dispersed Pt Nanoclusters Anchored on Sulfur-Doped Porous Carbon Carriers by Nanosecond Pulsed Laser for Hydrogen Evolution Reaction.

Nanosecond pulsed laser irradiation is employed for synthesis of highly active and stable Pt-based electrocatalysts by anchoring Pt nanoclusters on porous sulfur-doped carbon supports (L-Pt/SC). Strong metal-support interaction (SMSI) between Pt and S induces a local charge rearrangement and modulates the electronic structure of Pt surroundings, thus boosting the reaction kinetics and enhancing stability in long-term hydrogen evolution reaction (HER). The L-Pt/SC catalyst exhibits high activity toward HER, with an overpotential of 23 mV at current densities reaching 10 mA cm-2 and a Tafel slope of 24mV dec-1. The unit mass activity of L-Pt/SC is calculated to be -10.8 A cm-2 mgPt -1 at an applied voltage of -0.3V versus RHE. In situ Raman spectra reveals that L-Pt/SC catalyst exhibits fast hydrogen production efficiency and its electrocatalytic HER process is determined by the Tafel step. Density functional theory calculations suggest the strong bonding energy between SC and Pt induces the formation of smaller nanoclusters of L-Pt/SC during fast pulsed laser preparation, which increases the effective contact area during the HER process thereby increasing the activity per unit mass.

Green mediated sol-gel synthesis of MxCu1-xO (M = La,Ce x = 0.02–0.06) as an efficient catalyst for electrocatalytic oxygen evolution reaction

The imperative for advancing contemporary human society lies in the essential requirement to create energy generation systems that are sustainable, environmentally friendly, and exceptionally efficient. The development of efficient electrocatalysts, that are environmentally benign, economically viable and easily available, for alkaline oxygen evolution reaction is a significant research area in this regard. The present study focuses on a green mediated sol–gel auto-combustion process for the synthesis of lanthanum and cerium doped copper oxide nanoparticles with excellent electrocatalytic activity. Citric acid and polyols enriched lemon juice serves as the medium for the synthesis of various metal doped copper oxide nanoparticles. The extensive electrochemical studies using these catalysts reveals that, among the various doped samples, 5% lanthanum and 5% cerium doped catalysts exhibited the best performance in oxygen evolution reaction. Doping was found to enhance electrical conductivity and create oxygen vacancies, which enhanced the electrocatalytic activity of the catalysts. Specifically, the 5% lanthanum-doped copper oxide showed an overpotential of 340 mV, while the cerium-doped material exhibited an overpotential of 337 mV at a current density of 10 mA cm−2 in 1 M KOH. Moreover, the lanthanum-doped sample displayed a Tafel slope of 49 mV dec−1, whereas the cerium-doped sample had a Tafel slope of 60 mV dec−1 with better durability. Additionally, the chronopotentiometric studies revels the stability and long-term performance of LCO5 and CCO5, maintaining consistent potential of 1.58 V throughout 5 h at a current density of 10 mA cm−2. This study is conclusive evidence that the incorporation of rare earth elements improves the conductivity and overpotential of pristine copper oxide nanoparticles, making them highly effective in the oxygen evolution reactions.

Platinum/Platinum Sulfide on Sulfur-Doped Carbon Nanosheets with Multiple Interfaces toward High Hydrogen Evolution Activity.

Platinum (Pt)-based materials are among the most competitive electrocatalysts for the hydrogen evolution reaction (HER) due to suitable hydrogen adsorption energy. Due to the rarity of Pt, it is desirable to develop cost-effective Pt-based electrocatalysts with low Pt loading. Herein, Pt/PtS electrocatalysts on S-doped carbon nanofilms (PPS/C) have been successfully fabricated through a precursor reduction route with a complex of Pt and 1-dodecanethiol (1-DDT) as the precursor. The PPS/C achieved at 400 °C (PPS/C-400) exhibits excellent HER performances with an ultralow overpotential of 41.3 mV, a low Tafel slope of 43.1 mV dec-1 at a current density of 10 mA cm-2, and a long-term stability of 10 h, superior to many recently reported Pt-based HER electrocatalysts. More importantly, PPS/C-400 shows a high mass-specific activity of 0.362 A mgPt-1 at 30 mV, which is 1.88 times of that of commercial 20% Pt/C (0.193 A mgPt-1). The introduction of sulfur leads to the formation of PtS, which not only reduces the content of Pt but also realizes the interface regulation of Pt/PtS, as well as the doping of carbon. Both regulations make the resulting catalyst have abundant active centers and rapid electron transfer/transport, which is conducive to balancing the adsorption and resolution of intermediate products, and finally achieving great mass-specific activity and stability. The research work may provide ideas for designing effective Pt-based multi-interface electrocatalysts.

Enhancing Oxygen Evolution Reaction Performance with rGO/CoNi-Prussian Blue-Derived Oxyhydroxide Nanocomposite Electrocatalyst: A Strategic Synthetic Approach.

Electrochemical water splitting is a promising approach in the development of renewable energy technologies, providing an alternative to fossil fuels. It has attracted considerable attention in recent years. The benchmark materials used in water splitting are precious metals that are expensive and scarce. Therefore, this work proposes a strategic electrochemical synthesis of a reduced graphene oxide and cobalt-nickel hexacyanoferrate (rGO/CoNiHCF)-derived composite (rGO/CoNiPBd-OOH) to achieve optimized OER performance. The optimum rGO/CoNiHCF was fabricated with the Co:Ni precursors in a 3:1 ratio with a ferricyanide solution of pH = 1.0. Using an alkaline electrochemical treatment, the well-distributed globular particles of CoNiHCF over rGO sheets were converted into layered frameworks of metallic (oxy)hydroxide species, giving the final rGO/CoNiPBd-OOH nanocomposite. This nanocomposite presented favorable kinetic activity resulting in a Tafel slope of 33 mV dec-1, while rGO, CoNiPBd-OOH, and RuO2 exhibited slopes of 80, 47, and 51 mV dec-1, respectively. Although the benchmark RuO2 electrocatalyst showed a lower overpotential (240 mV dec-1) at a current density of 10 mA cm-2, the rGO/CoNiPBd-OOH performed well with an overpotential of 346 mV, combined with superior stability compared to CoNiPBd-OOH and RuO2, maintaining a current density of 10 mA cm-2 for 15 h with an overpotential loss of 6.92%. This work successfully presents an "all-electrochemical" synthesis of a rGO/CoNiHCF-derived material with remarkable electrocatalytic activity for OER assisted by a strategic preparation methodology, which helped to understand the influence of synthetic parameters and choose their conditions to achieve the optimum OER performance.

Enhanced electrochemical performance of ZrTe-Mn2O3 nanocomposite electrocatalyst for HER and OER in alkaline medium

Electrochemical energy conversion in renewable-energy technologies relies on the OER and HER towards next-generation fuels. Herein, we have coupled zirconia telluride (ZrTe) and manganese oxide (Mn2O3) nanosheets heterointerfaces by a facile hydrothermal method, which are engineered on stainless steel substrate (ZrTe-Mn2O3/SS). The physical properties, including crystallinity, phase purity, morphology, conductivity, and chemical interacted states of the developed composite, are systematically investigated by XRD, HRTEM, I-V, and XPS. The XPS observation showed unique redox properties of hydrogen peroxide species on the ZrTe-Mn2O3 catalyst and the oxidation state of Zr and Mn that was more easily changed in the ZrTe-Mn2O3 electrocatalyst compared with the pristine catalysts. The very decent electrochemical performance of the catalyst activation step (Mn3+→Mn4+ and Zr2+→Zr4+ oxidations) observed from electrochemical cyclic voltammetry (CV) and linear sweep voltammetry (LSV) studies that are tested in the alkaline environment. Concerning higher bifunctional activity for ZrTe-Mn2O3, the current density of 10 mA cm−2 is revealed only at a lower overpotential of 244 mV and Tafel slope of 48 mV/dec toward better OER. At the same time, composite material also exhibited a minimal overpotential of 61 mV toward HER to attain 100 mA/cm2. It was also found that introducing a connection of ZrTe with Mn2O3 improves the precise surface area and exposes more multi-active sites for easy transfer of electrons. In addition, it maintains excellent long-term stability for almost 110 hrs through chronoamperometry, which leads to no activity loss and further represents higher OER/HER activity in industrial applications. We conclusively demonstrate that the first-time reported research provides valuable insights attributed to the defective structure, porous nature, and covalently bridging between atomic-level heterogeneous interfaces, favouring rapid electron transfer process activation for continuously produced O2 and H2 gas bubbles.

Co-complexes on modified graphite surface for steady green hydrogen production from water at neutral pH.

Green hydrogen production from water is one attractive route to non-fossil fuel and a potential source of clean energy. Hydrogen is not only a zero-carbon energy source but can also be utilized as an efficient storage of electrical energy generated through various other sources, such as wind and solar. Cost-effective and environmentally benign direct hydrogen production through neutral water (∼pH 7) reduction is particularly challenging due to the low concentration of protons. There is currently a major need for easy-to-prepare, robust, as well as active electrode materials. Herein we report three new molecular electrodes that were prepared by anchoring commercially available, and environmentally benign cobalt-containing electrocatalysts with three different ligand frameworks (porphyrin, phthalocyanine, and corrin) on a structurally modified graphite foil surface. Under the studied reaction conditions (over 7h at 22°C), the electrode with Co-porphyrin is the most efficient for the water reduction with starting ∼740mV onset potential (OP) (vs. RHE, current density 2.5mA/cm2) and a Tafel slope (TS) of 103mV/dec. It is followed by the molecular electrodes having Co-phthalocyanine [825mV (OP), 138mV/dec (TS)] and Vitamin-B12 (Co-corrin moiety) [830mV (OP), 194 mv/dec (TS)]. A clear time-dependent improvement (>200mV over 3h) in the H2 production overpotential with the Co-porphyrin-containing cathode was observed. This is attributed to the activation due to water coordination to the Co-center. A long-term chronopotentiometric stability test shows a steady production of hydrogen from all three cathode surfaces throughout seven hours, confirmed using an H2 needle sensor. At a current density of 10mA/cm2, the Co-porphyrin-containing electrode showed a TOF value of 0.45s-1 at 870mV vs. RHE, whereas the Co-phthalocyanine and Vitamin-B12-containing electrodes showed 0.37 and 0.4s-1 at 1.22V and 1.15V (vs. RHE), respectively.

Accelerated Electrons Transfer and Synergistic Interplay of Co and Ge Atoms (111 Crystal Plane) Activated by Anchoring Nano Spinel Structure Co2GeO4 onto Carbon Cloth Composite Electrocatalyst for Highly Enhanced Hydrogen Evolution Reaction

The electrochemical hydrogen evolution reaction (HER) was considered to be a promising strategy for future clean energy. In this work, a composite electrocatalyst (designated as CGO36@CC) was synthesized through anchoring of nano spinel structure Co2GeO4 onto carbon cloth fibers and exhibited outstanding electrocatalytic performance for HERs in an alkaline medium. The characterization outcome established that, after 36 h of hydrothermal reaction, nano spinel structure Co2GeO4 particles (exposed abundant 111 crystal planes) were stably loaded onto a carbon cloth fiber surface, and this structural configuration facilitated the electrons transferring between each other. In addition, the electrochemical analysis revealed that the incorporation of nano spinel structure Co2GeO4 and carbon cloth significantly augmented the electrochemical activity value of the composite and efficiently enhanced the HER performance. Notably, the overpotential was merely 96 mV at 10 mA·cm−2 current density, and the Tafel slope was only 48.9 mV·dec−1. Moreover, CGO36@CC displayed remarkable catalytic activity and sustained HER catalytic stability. The theoretical catalytic prowess of CGO36@CC stemmed from the collaborative influence of germanium and cobalt atoms within the exposed 111 crystal plane of the Co2GeO4 molecular framework. The amalgamation of Co2GeO4 with carbon cloth fiber conferred upon the composite electrocatalyst both superior theoretical catalytic activity and enhanced electron transfer capability. This work provides a novel strategy for exploring a highly efficient composite electrocatalyst combined transition metal with carbon material to accelerate the HER activity.

Enhanced oxygen evolution reaction performance using amorphous hollow cerium-doped cobalt phosphate derived from ZIF-67 structures

A major obstacle in achieving massive operations water splitting is the slow rate of the anodic reaction. To address this issue, metal phosphates have been extensively employed as efficient materials for the oxygen evolution reaction (OER). In this study, ZIF-67 structures were synthesized in both single-metal and bimetallic forms with different molar ratios of cerium. The structure with the best electrochemical activity ((5 present) cerium doped ZIF-67 ((5)CeZIF-67)) was subjected to a phosphatization process, resulting in the formation of the amorphous and hollow cerium doped cobalt phosphate (Ce-CPO) structure as a novel and highly efficient OER electrocatalyst. To the best of authors knowledge, this is the first report on the synthesis and application of Ce-CPO structure for boosting OER process. This resultant structure exhibited suitable electrochemical performance in the oxygen evolution reaction (OER), achieving an overpotential of 286 mV at a current density of 30 mA cm−2 and a Tafel slope of 74.4 mV decade−1. Furthermore, the final structure demonstrated satisfactory stability during a 10 h operation period. The notable improvement in the Ce-CPO structure was due to the use of a bimetallic framework combined with phosphorus and an amorphous porous structure. The distinctive configuration achieved greatly amplifies the effective surface area, hence improving electron transfer. The findings of this research can contribute to the development of electrodes with improved performance in OER.

Unlocking interfacial effects in NiTiO3-TiO2 eutectic composite: Enhancing overall electrocatalytic and photoelectrochemical water splitting

This study introduces a novel approach to tackle the urgent demand for catalysts possessing both bifunctional capabilities and efficient photocatalytic properties. By employing the micro-pulling down method, a NiTiO3/TiO2 eutectic composite is synthesized, creating an interface rich structure. This composite is utilized as a photo-anode, displaying a significant photocurrent of 3.5 mA/cm2 at 1.4 V. Through annealing in an H2 atmosphere, the catalytic performance is finely adjusted, revealing distinct electrochemical activities at the interface of NiTiO3 and TiO2. Enhanced interfacial adsorption is confirmed by scanning electrochemical microscopy post-annealing. Remarkably, the annealed NiTiO3/TiO2 exhibits outstanding overall water-splitting efficiency, with minimal overpotentials of 80 mV (at 10 mA/cm2) and 120 mV (at 50 mA/cm2) for the HER and OER, respectively. The low Tafel slope (41 mV dec-1) underscores rapid water splitting kinetics. Density functional theory (DFT) calculations suggest that NiTiO3-TiO2 heterostructure can enhanced the catalytic properties of the surface providing higher adsorption of the electrolyte ions during catalytic reactions. This study establishes a straightforward crystal growth strategy for the design of highly effective, enduring, and bifunctional photocatalytic catalysts, signaling promising advancements in water splitting technology.

Monitoring Electrochemical Dynamics through Single-Molecule Imaging of hBN Surface Emitters in Organic Solvents.

Electrochemical techniques conventionally lack spatial resolution and average local information over an entire electrode. While advancements in spatial resolution have been made through scanning probe methods, monitoring dynamics over large areas is still challenging, and it would be beneficial to be able to decouple the probe from the electrode itself. In this work, we leverage single molecule microscopy to spatiotemporally monitor analyte surface concentrations over a wide area using unmodified hexagonal boron nitride (hBN) in organic solvents. Through a sensing scheme based on redox-active species interactions with fluorescent emitters at the surface of hBN, we observe a region of a linear decrease in the number of emitters against increasingly positive potentials applied to a nearby electrode. We find consistent trends in electrode reaction kinetics vs overpotentials between potentiostat-reported currents and optically read emitter dynamics, showing Tafel slopes greater than 290 mV·decade-1. Finally, we draw on the capabilities of spectral single-molecule localization microscopy (SMLM) to monitor the fluorescent species' identity, enabling multiplexed readout. Overall, we show dynamic measurements of analyte concentration gradients on a micrometer-length scale with nanometer-scale depth and precision. Considering the many scalable options for engineering fluorescent emitters with two-dimensional (2D) materials, our method holds promise for optically detecting a range of interacting species with exceptional localization precision.

Interfacial Regulation of Rice-Grain-like Iron-Nickel Phosphide Nanorods on Phosphorus-Doped Graphene Architectures as Bifunctional Electrocatalysts for Water Splitting.

The design of bimetallic metal-organic frameworks (MOFs) with a hierarchical structure is important to improve the electrocatalytic performance of catalysts due to their synergistic effect on different metal ions. In this work, the catalyst comprises bimetallic iron-nickel MOF-derived FeNi phosphides, intricately integrated with phosphorus-doped reduced graphene oxide architectures (FeNi2P-C/P-rGA) through the hydrothermal and phosphating treatments. The hierarchical architecture of the catalyst is beneficial for exposing active sites and facilitating electron transfer. The FeNi2P-C/P-rGA catalyst exhibits excellent performance in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolytes. Notably, FeNi2P-C/P-rGA requires only the overpotential of 93 and 210 mV to achieve a current density of 10 mA cm-2 for the HER and OER with small values of Tafel slope and charge transfer resistance, respectively. Furthermore, the catalyst exhibits boosted activity for overall water splitting with a low potential of 1.56 V. This work can be considered to extend the design of multilevel catalysts in the application of water splitting.

Designing Bifunctional Electrocatalysts Based on Complex Cobalt-Sulfo-Boride Compound for High-Current-Density Alkaline Water Electrolysis.

In the quest to harness renewable energy sources for green hydrogen production, alkaline water electrolysis has emerged as a pivotal technology. Enhancing the reaction rates of overall water electrolysis and streamlining electrode manufacturing necessitate the development of bifunctional and cost-effective electrocatalysts. With this aim, a complex compound electrocatalyst in the form of cobalt-sulfo-boride (Co-S-B) was fabricated using a simple chemical reduction method and tested for overall alkaline water electrolysis. A nanocrystalline form of Co-S-B displayed a combination of porous and nanoflake-like morphology with a high surface area. In comparison to Co-B and Co-S, the Co-S-B electrocatalyst exhibits better bifunctional characteristics requiring lower overpotentials of 144 mV for hydrogen evolution reaction and 280 mV for oxygen evolution reaction to achieve 10 mA/cm2 in an alkaline electrolyte. The improved Co-S-B performance is attributed to the synergistic effect of sulfur and boron on cobalt, which was experimentally confirmed through various material characterization tools. Tafel slope, electrochemical surface area, turnover frequency, and charge transfer resistance further endorse the active nature of the Co-S-B electrocatalyst. The robustness of the developed electrocatalyst was validated through a 50 h chronoamperometric stability test, along with a recyclability test involving 10,000 cycles of linear sweep voltammetry. Furthermore, Co-S-B was tested in an alkaline zero-gap water electrolyzer, reaching 1 A/cm2 at 2.06 V and 60 °C. The significant activity and stability demonstrated by the cobalt-sulfo-boride compound render it as a promising and cost-effective electrode material for commercial alkaline water electrolyzers.

Insights into the structural, dielectric, optical and electrochemical characteristics reveal the limiting parameters toward efficient OER catalysts in the perovskite solid solution Sr1-xLaxTi1-xFexO3 (0.2 ≤ x ≤ 0.8)

Due to their structural stability and flexibility, perovskite oxides have paved their way as oxygen evolution reaction (OER) electrocatalysts. The in-depth understanding of the limiting factors toward good activity and fast charge transfer are still considered as major challenges for highly active OER perovskite catalysts. In this work, we disclose the changes in the perovskite structure and properties that influence the activity as we introduce new criteria to be considered for perovskites electrocatalysts design. The activity test of the series Sr1-xLaxTi1-xFexO3 (0.2 ≤ x ≤ 0.8) reveals the overpotential of 300 mV @ 10 mA.cm−1, and Tafel slop of 57.6 mV dec−1, as the lowest values corresponding to the composition x = 0.4. As function of the composition, the dielectric constant is found to decrease from 3000 (x = 0.2) to 953 (x = 0.4), and increases up to 5497 (x = 0.8). This variation of the dielectric constant is found to influence the activity of the catalysts where lowest overpotential of 300 mV @ 10 mA.cm−1 is found for x = 0.4 with the smallest dielectric constant. The phase transition detected in the perovskite series upon substitution has induced a distortion in the unit cell, which is found to be in alignment with the evolution of the overpotential in the perovskites series. The distortion has induced a preferable octahedra orientation for efficient OER reaction, this orientation correspond to the interatomic distance <Ti/Fe-O2> (1) = 1.89 Å and <Ti/Fe-O2> (2) = 2.04 Å (x=0.4) with the condition of <Ti/Fe-O2> (1) remains shorter than <Ti/Fe-O2> (2). The band gap, thus the conduction and valence bands edges, is found to decrease with the increase of the interatomic distance (Fe/Ti-O) and with the deviation of the Bond angle (B)-O2-(B) from the ideal value of 180°. These findings put light on the limiting factors of the perovskites activity by linking the structural parameters and the physical properties with the objective of accurately designing highly-efficient perovskite OER electrocatalysts.

Enhanced oxygen evolution and power density of Co/Zn@NC@MWCNTs for the application of zinc-air batteries

Rechargeable zinc-air batteries (ZABs) are viewed as a promising solution for electric vehicles due to their potential to provide a clean, cost-effective, and sustainable energy storage system for the next generation. Nevertheless, sluggish kinetics of the oxygen evolution reaction (OER), the oxygen reduction reaction (ORR) at the air electrode, and low power density are significant challenges that hinder the practical application of ZABs. The key to resolving the development of ZABs is developing an affordable, efficient, and stable catalyst with bifunctional catalytic. In this study, we present a series of bifunctional catalysts composed of Co/Zn nanoparticles uniformly embedded in nitrogen-doped carbon (NC) and multi-walled carbon nanotubes (MWCNTs) denoted as Co/Zn@NC@MWCNTs. The incorporation of MWCNTs using a facile and non-toxic method significantly decreased the overpotential of the OER from 570 to 430 mV at 10 mA cm−2 and the peak power density from 226 to 263 mW cm−2. Besides, the electrochemical surface area measurements and electrochemical impedance spectroscopy indicate that the three-dimensional (3D) network structure of MWCNTs facilitates mass transport for ORR and reduces electron transfer resistance during OER, leading to a small potential gap of 0.86 V between OER and ORR, high electron transfer number (3.92–3.98) of the ORR, and lowest Tafel slope (47.8 mV dec−1) of the OER in aqueous ZABs. In addition, in-situ Raman spectroscopy revealed a notable decrease in the ID/IG ratio for the optimally configured Co/Zn@NC@MWCNTs (75:25), indicating a reduction in defect density and improved structural ordering during the electrochemical process, which directly contributes to enhanced ORR activity. Hence, this study provides an excellent strategy for constructing a bifunctional catalyst material with a 3D MWCNTs conductive network for the development of advanced ZAB systems for sustainable energy applications.

Coupling highly reactive RuP2 with amorphous WP for boosting alkaline hydrogen evolution

Electrochemical water splitting stands out as an environmentally benign approach for generating green H2 through the harnessing of intermittent energy derived from renewable sources. However, the slow water dissociation kinetics hinders the commercialization for water-alkali electrolyzer. In this study, we synthesize a novel porous nanocomposite (RuP2/WP/PNC3-A) combined with RuP2 and amorphous WP by a facile and eco-friendly strategy. Detailed research results demonstrate that biomass-derived phytic acid not only promotes the formation of active metal phosphides, but also serves as a pore-forming agent to assist in the constructing a hierarchical porous structure, significantly enhancing the mass and electron transfer capability. Particularly noteworthy is that WP prevents the aggregation of RuP2. During the post-treatment process more protected RuP2 components are released and meanwhile leads to the conversion of WP from crystalline to amorphous. Benefitting from the applicable H adsorption ability of RuP2 and the enhanced H2O adsorption, dissociation capacity by amorphous WP, RuP2/WP/PNC3-A exhibits astonishing hydrogen evolution reaction (HER) performance, requiring an exceedingly low overpotential (only 24 mV) under 10 mA cm−2, featuring small Tafel slope (64.6 mV dec−1), and demonstrating excellent durability.

Low loading of Pt on MoB Constructed by microwave Quasi-solid approach with solvent Regulation for hydrogen evolution reaction

The interaction between metal nanoclusters and the carrier can enhance the electron transfer rate to optimize the hydrogen evolution reaction (HER) performance, but the common synthesis approaches often lead to metal particle agglomeration, and then blocking active sites. Herein, highly-dispersed Pt nanoclusters supported onto molybdenum boride (MoB) is developed through microwave approach with various solvent to regulate the catalytic performance. The synthesized electrocatalyst with the addition of methanol (Pt/MoB-M) exhibits excellent electrocatalytic performance towards HER with low overpotential (13 mV at 10 mA cm−2), small Tafel slope (24 mV dec−1), and high mass activity (10.06 A/mgPt at 50 mV). This work presents a novel approach to prepare highly-efficient electrocatalysts for renewable energy-related applications of non-carbon supported low loading of precious metals.

In-Situ Construction of Fe-Doped NiOOH on the 3D Ni(OH)2 Hierarchical Nanosheet Array for Efficient Electrocatalytic Oxygen Evolution Reaction.

Accessible and superior electrocatalysts to overcome the sluggish oxygen evolution reaction (OER) are pivotal for sustainable and low-cost hydrogen production through electrocatalytic water splitting. The iron and nickel oxohydroxide complexes are regarded as the most promising OER electrocatalyst attributed to their inexpensive costs, easy preparation, and robust stability. In particular, the Fe-doped NiOOH is widely deemed to be superior constituents for OER in an alkaline environment. However, the facile construction of robust Fe-doped NiOOH electrocatalysts is still a great challenge. Herein, we report the facile construction of Fe-doped NiOOH on Ni(OH)2 hierarchical nanosheet arrays grown on nickel foam (FeNi@NiA) as efficient OER electrocatalysts through a facile in-situ electrochemical activation of FeNi-based Prussian blue analogues (PBA) derived from Ni(OH)2. The resultant FeNi@NiA heterostructure shows high intrinsic activity for OER due to the modulation of the overall electronic energy state and the electrical conductivity. Importantly, the electrochemical measurement revealed that FeNi@NiA exhibits a low overpotential of 240 mV at 10 mA/cm2 with a small Tafel slope of 62 mV dec-1 in 1.0 M KOH, outperforming the commercial RuO2 electrocatalysts for OER.