Low Tafel Slope Research Articles

Designing ternary Co-Ni-Fe layered double hydroxides within a novel 3D cross-flower framework for efficient catalytic performance in oxygen evolution reaction

In this study, we synthesized novel three-dimensional (3D) cross-flowered Co-Ni metal–organic framework (Co-Ni-MOF) precursors using the chemical precipitation method. Subsequently, we obtained Co-Ni-Fe layered double hydroxides (Co-Ni-Fe-LDHs) through an ion exchange strategy, which preserved their original morphology while consisting of ultrathin layered hydroxide nanosheets. The interlayer spacing of the LDH lamellar structure was finely tuned by varying the ratios of Co to Ni. The results demonstrated that Co-Ni-Fe LDHs, characterized by a unique three-dimensional cross-shaped structure and an optimal composition ratio of Co2+:Ni2+ = 2:1, exhibited increased interlayer spacing. This structural characteristic contributed to their excellent electrochemical performance, positioning them as optimal electrode materials for catalytic oxygen evolution reactions (OER). Our observations revealed that Co-Ni-Fe-LDHs exhibited remarkable OER activity, characterized by a low Tafel slope of 41.82 mV dec−1, a low overpotential of 322 mV at a current density of 10 mA cm−2, and outstanding stability over a 48-hour period. In-situ Raman spectroscopy results indicated that the active site of the composite was γ-CoOOH. Additionally, the room temperature stirring and standing strategy employed in this study is easier to scale up and yields a higher quantity of reaction products compared to traditional high-temperature and high-pressure conditions. This investigation provides novel insights into the design and fabrication of Co-Ni-Fe-LDHs catalyst with 3D cross-flower structures, demonstrating enhanced electrocatalytic activity and commendable stability. These findings suggest promising applications in the field of electrolyzed water.

WS2 Moiré Superlattices Supporting Au Nanoclusters and Isolated Ru to Boost Hydrogen Production.

Maximizing the catalytic activity of single-atom and nanocluster catalysts through the modulation of the interaction between these components and the corresponding supports is crucial but challenging. Herein, guided by theoretical calculations, a nanoporous bilayer WS2 Moiré superlattices (MSLs) supported Au nanoclusters (NCs) adjacent to Ru single atoms (SAs) (Ru1/Aun-2LWS2) is developed for alkaline hydrogen evolution reaction (HER) for the first time. Theoretical analysis suggests that the induced robust electronic metal-support interaction effect in Ru1/Aun-2LWS2 is prone to promote the charge redistribution among Ru SAs, Au NCs, and WS2 MSLs support, which is beneficial to reduce the energy barrier for water adsorption and thus promoting the subsequent H2 formation. As feedback, the well-designed Ru1/Aun-2LWS2 electrocatalyst exhibits outstanding HER performance with high activity (η10=19mV), low Tafel slope (35mVdec-1), and excellent long-term stability. Further, in situ, experimental studies reveal that the reconstruction of Ru SAs/NCs with S vacancies in Ru1/Aun-2LWS2 structure acts as the main catalytically active center, while high-valence Au NCs are responsible for activating and stabilizing Ru sites to prevent the dissolution and deactivation of active sites. This work offers guidelines for the rational design of high-performance atomic-scale electrocatalysts.

Cobalt-doped graphitic carbon nitride: A multifunctional material for humidity sensing, electrochemical water splitting and environmental remediation applications

Graphitic carbon nitride (g-C3N4) has emerged as a promising eco-friendly material for catalysis and sensing applications due to their unique properties. However, limitations like low specific surface area, insufficient light absorption, and poor conductivity hinder their broader usability. Elemental doping has been established as an effective approach to modify the electronic structure and bandgap of g-C3N4 thus significantly expanding its light-responsive range for enhanced charge separation. This work reports on the fabrication of cost-effective and stable g-C3N4 and cobalt-doped g-C3N4 (Co@g-C3N4) via a simple one-step calcination process. The humidity sensing performance of both g-C3N4 and Co@g-C3N4 was evaluated across a broad humidity range (7 % - 94 % RH) at various testing frequencies. The results demonstrated good reversibility with Co@g-C3N4 exhibiting superior performance compared to pristine g-C3N4. Furthermore, the synthesized materials were assessed for their suitability as photoelectrochemical water splitting catalysts for hydrogen production, representing a step towards energy-efficient fuel cells. Notably, Co@g-C3N4 displayed enhanced performance with a lower onset potential (420 mV) and a lower Tafel slope (65.4 mV dec-1) for the hydrogen evolution reaction (HER) compared to undoped counterparts. Additionally, Co@g-C3N4 nanorods exhibited remarkable performance for the oxygen evolution reaction (OER), showcasing a lower onset potential (1.505 V) and a considerably low overpotential (270 mV), surpassing numerous reported electrocatalysts and even rivaling precious-metal-based ones. Finally, enhanced photocatalytic activities for organic dyes degradation were recorded for the mentioned materials. Therefore, g-C3N4 and related materials have great potential for their industrial electrochemcial applications.

Trifunctional Graphene-Sandwiched Heterojunction-Embedded Layered Lattice Electrocatalyst for High Performance in Zn-Air Battery-Driven Water Splitting.

Zn-air battery (ZAB)-driven water splitting holds great promise as a next-generation energy conversion technology, but its large overpotential, low activity, and poor stability for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) remain obstacles. Here, a trifunctional graphene-sandwiched, heterojunction-embedded layered lattice (G-SHELL) electrocatalyst offering a solution to these challenges are reported. Its hollow core-layered shell morphology promotes ion transport to Co3S4 for OER and graphene-sandwiched MoS2 for ORR/HER, while its heterojunction-induced internal electric fields facilitate electron migration. The structural characteristics of G-SHELL are thoroughly investigated using X-ray absorption spectroscopy. Additionally, atomic-resolution transmission electron microscopy (TEM) images align well with the DFT-relaxed structures and simulated TEM images, further confirming its structure. It exhibits an approximately threefold smaller ORR charge transfer resistance than Pt/C, a lower OER overpotential and Tafel slope than RuO₂, and excellent HER overpotential and Tafel slope, while outlasting noble metals in terms of durability. Ex situ X-ray photoelectron spectroscopy analysis under varying potentials by examining the peak shifts and ratios (Co2+/Co3+ and Mo4+/Mo6+) elucidates electrocatalytic reaction mechanisms. Furthermore, the ZAB with G-SHELL outperforms Pt/C+RuO2 in terms of energy density (797Wh kg-1) and peak power density (275.8mW cm-2), realizing the ZAB-driven water splitting.

Fabrication of abundant oxygen vacancies in MOF-derived (Fe,Co)3O4 for oxygen evolution reaction and as an air cathode for zinc-air batteries

Metal-organic frameworks (MOFs) find wide-ranging applications owing to their adjustable structures, diverse compositions, and large specific surface area. In this work, MOFs materials were grown in situ on carbon cloth, yielding self-supported electrodes VO-(Fe,Co)3O4@CC rich in oxygen vacancies through a simple high-temperature annealing treatment utilizing NaBH4 as an etchant. Thus the resulting self-supported electrode VO-(Fe,Co)3O4@CC exhibited excellent oxygen evolution reaction (OER) performance, achieving an overpotential of merely 288 mV at 10 mA cm−2, along with a low Tafel slope of 31.39 mV dec-1, and demonstrating robust long-term activity and stability. In addition, a liquid zinc-air battery was assembled utilizing the prepared VO-(Fe,Co)3O4@CC as an air cathode, achieving a high open-circuit voltage of 1.46 V and a high peak power density of 89.06 mW cm−2, and it maintained excellent cycling stability during cyclic charging and discharging (with a current density of 2 mA cm−2) over a 32 h period. Meanwhile, the self-supported electrode VO-(Fe,Co)3O4@CC served as an air cathode for assembling an all-solid-state flexible zinc-air battery (ZAB), demonstrating a high peak power density (38.21 mW cm−2) and exhibiting favorable cycling stability. This experiment offers insights into the potential application of MOF-derived electrocatalysts in water decomposition and zinc-air batteries.

Ultrafast joule-heating synthesis of FeCoMnCuAl high-entropy-alloy nanoparticles as efficient OER electrocatalysts

High entropy alloys (HEAs), known for their synergistic orbital interactions among multiple elements, have been recognized as promising electrocatalysts for enhancing the sluggish kinetics of oxygen evolution reaction (OER). Despite their potential, the facile and rapid preparation of HEA nanoparticles (NPs) with high electrocatalytic activity remains challenging. Here, we report an ultrafast synthesis of noble-metal-free FeCoMnCuAl HEA NPs loaded on conductive carbon fiber networks using a Joule heating strategy. The prepared HEA NPs exhibited a face-centered cubic (FCC) structure with an average size of approximately 25 ​nm. Synchrotron X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) studies were performed to investigate the atomic and electronic structures of the HEA NPs, revealing the co-presence of Fe, Co, Mn, Cu and Al elements as well as their different valences across surface and internal regions. The HEA NPs showed remarkable OER performance, exhibiting an overpotential of 280 ​mV at 10 ​mA ​cm−2 and a low Tafel slope of 76.13 ​mV dec−1 in a 1.0 ​M KOH solution with high electrochemical stability, superior to commercial RuO2 electrocatalysts. This work provides a new approach for synthesizing nanoscale noble-metal-free HEA electrocatalysts for clean energy conversion applications on a large-scale basis for practical commercialization.

Nickel-Iron Layered Double Hydroxides/Nickel Sulfide Heterostructured Electrocatalysts on Surface-Modified Ti Foam for the Oxygen Evolution Reaction.

Electrochemical approaches for generating hydrogen from water splitting can be more promising if the challenges in the anodic oxygen evolution reaction (OER) can be harnessed. The interface heterostructure materials offer strong electronic coupling and appropriate charge transport at the interface regions, promoting accessible active sites to prompt kinetics and optimize the adsorption-desorption of active species. Herein, we have designed an efficient multi-interface-engineered Ni3Fe1 LDH/Ni3S2/TW heterostructure on in situ generated titanate web layers from the titanium foam. The synergistic effects of the multi-interface heterostructure caused the exposure of rich interfacial electronic coupling, fast reaction kinetics, and enhanced accessible site activity and site populations. The as-prepared electrocatalyst demonstrates outstanding OER activity, demanding a low overpotential of 220 mV at a high current density of 100 mA cm-2. Similarly, the designed Ni3Fe1 LDH/Ni3S2/TW electrocatalyst exhibits a low Tafel slope of 43.2 mV dec-1 and excellent stability for 100 h of operation, suggesting rapid kinetics and good structural stability. Also, the electrocatalyst shows a low overpotential of 260 mV at 100 mA cm-2 for HER activity. Moreover, the integrated electrocatalyst exhibits an incredible OER activity in simulated seawater with an overpotential of 370 mV at 100 mA cm-2 and stability for 100 h of operation, indicating good OER selectivity. This work might benefit further fabricating effective and stable self-sustained electrocatalysts for water splitting in large-scale applications.

Defect engineering via gamma irradiation in scalable mechanical exfoliation TMDs thin films for improved electrocatalytic hydrogen evolution

This study explores a novel and efficient van der Waals thin-film deposition method, called Automatic Mechanical Exfoliation (AME), and its application in hydrogen evolution reaction (HER). Compared to traditional physical deposition techniques, AME offers significant advantages: it is simpler, more cost-effective, and significantly faster, enabling the deposition of large-area (>5 cm2) coatings exhibiting superior catalytic activity towards HER. To demonstrate its versatility, we comprehensively characterized large-area TMD thin films (MoS2/NbS2, NbS2, TiS2, MoSe2, MoS2, and WS2) using various techniques. Our AME-grown TMD thin films delivered improved HER performance, with lower Tafel slopes compared to previously reported values. To further enhance their activity, we irradiated the films with gamma radiation, leading to a remarkable improvement across all studied TMDs materials (e.g., an average increase of 30 % in exchange current density). Notably, NbS2 thin films and MoS2/NbS2 heterostructures exhibited excellent performance after irradiation, achieving low Tafel slopes (81 mV/dec and 85 mV/dec, respectively), starting overpotentials (−56 mV and −24 mV vs RHE, respectively), high exchange current densities (10.39 µA cm–2 and 625.2 µA cm–2, respectively), and turnover frequencies (0.021 s–1 and 0.95 s–1, respectively). These findings suggest that gamma irradiation can be a powerful tool for defect engineering in TMDs, creating additional active sites and demonstrably enhancing their catalytic efficiency for HER.

Simultaneously Boosting Direct and Indirect Urea Oxidation of Nickel Hydroxide via Strategic Yttrium Doping.

Urea electrolysis can address pressing environmental concerns caused by urea-containing wastewater while realizing energy-saving hydrogen production. Highly efficient and affordable electrocatalysts are indispensable for realizing the great potential of this emerging technology. Among the numerous candidates, α-Ni(OH)2 has the merits of good electrocatalytic activity, adjustable heteroelement doping, and low cost; consequently, it has received tremendous attention in the electrolytic fields. Herein, a Y3+-doping strategy is developed to effectively enhance the catalytic performance of nickel hydroxide in the urea oxidation reaction (UOR). Our results show that Y3+ incorporation successfully modulates the electronic structure of α-Ni(OH)2 by inducing Ni3+ formation in the crystal lattice to initiate direct UOR, facilitates the Ni3+/Ni2+ redox transition with higher current responses to promote indirect UOR, and maintains the structural stability of YNi-10 (Ni2+/Y3+ molar ratio = 1:0.1) during long-term UOR operation. Owing to these features, the obtained YNi-10 sample exhibits a higher current density (127 vs 79 mA cm-2 at 1.5 V), a lower Tafel slope (48 vs 75 mV dec-1), a larger potential difference between the UOR and oxygen evolution reaction (OER, 0.26 vs 0.22 V at 80 mA cm-2), a higher reaction rate constant (1.1 × 105 vs 3.1 × 103 cm3 mol-1 s-1), and a reduced activation energy of UOR (2.9 vs 14.8 kJ mol-1) compared with the Y-free counterpart (YNi-0). This study presents a promising strategy to simultaneously boost direct and indirect UORs, providing new insights for further developing high-performance electrocatalysts.

Facile synthesis of Co-doped In2O3 integrated with tubular g-C3N4 heterostructure and their synergistic effect on the enhanced photocatalytic degradation of tetracycline and oxygen evolution reaction

In this work, we developed cost-effective and environmentally friendly bifunctional catalysts for energy and environmental applications. Tubular graphitic carbon nitrides (TCN), In2O3, In2O3/TCN, and x% cobalt (Co) doped In2O3/TCN (x = 1 %, 3 %, and 5 wt% of Co) composite materials synthesized by polymerization and hydrothermal methods. The photocatalytic activity of these materials was tested for tetracycline (TC) removal under sunlight and visible light illumination. Among them, 5 % Co-In2O3/TCN composite exhibited the highest photocatalytic efficiency, achieving 100 % and 94 % TC degradation under sunlight and visible light, respectively. PL analysis indicated that the 5 % Co-In2O3/TCN composite exhibited superior charge separation efficiency. Scavenging tests confirmed that holes (h+) and superoxide radicals (O2•−) play important roles in the photocatalytic process. The electrochemical performance of the prepared materials was investigated in 1.0 M KOH. Among the catalysts, the 5 % Co-In2O3/TCN@nickel foam (NF) composite showed the best oxygen evolution reaction (OER) performance with low overpotential (240 mV) and Tafel slope (95 mV/dec) and maintained stability for more than 24 h at 10 mA/cm2. An electrolyzer using 5 % Co-In2O3/TCN@NF||Pt/C@NF catalyst achieved cell voltages of 1.73 V and 2.23 V at 10 mA/cm² and 100 mA/cm², respectively. In this study, we developed low-cost photo and electrocatalysts that exhibited excellent environmental remediation and energy production capabilities.

In-situ growth strategy to synthesize porous nano-coral-like structure OER catalyst based on nife foam alloy substrate

The preparation of alloy-based catalysts is an effective approach to simplify the catalyst synthesis process for electrocatalysis. The oxygen evolution reaction (OER) is considered a key step in water splitting. By incorporating interface engineering design, electronic state optimization, and heteroatom doping, the electrocatalytic performance can be enhanced. In this study, a simple method was used to activate the NiFe foam (NIF) alloy substrate by acid etching, followed by in-situ S-doping of Cr via a hydrothermal method to synthesize S-Cr0.6@NiFe/NIF catalyst material. Its outstanding porous nanocoral-like structure not only provides abundant active sites but also exhibits superior catalytic water splitting performance, demonstrating superhydrophilic and superaerophobic characteristics. At a current density of 10 mA cm−2, only 262 mV overpotential is required to drive the OER (under basic conditions of 1 M KOH), with a low Tafel slope (71.6 mV dec−1) and a large electrochemical active surface area (ECSA = 85.25 cm2). After 80 hours of OER test, the current density of S-Cr0.6@NiFe/NIF shows negligible change. This study provides an attractive, effective, and feasible method for the in-situ growth design of alloy-based catalysts.

Electrocatalytic micro-environment regulation of ZIF-67 with broadened pore structure and unsaturated coordination sites for oxygen evolution reaction

The atomically precise mental nanoclusters have been widely explored in catalysis. However, the easy aggregation of clusters limits their application. The porous structure of metal-organic framework can prevent the aggregation and growth of clusters. In this work, a copper-phosphine complex: Cu2(dppm)2(PF6)2 (Cu2) was synthesized by one-pot method and then reacted with hydrogen sulfide to obtain a tetranuclear copper cluster: Cu4(S)(dppm)4(PF6)2 (Cu4). The two copper clusters were successfully introduced into Zeolitic imidazole frameworks-67 (ZIF-67) to form Cu2-ZIF-67 and Cu4-ZIF-67. It found that after the introduction of Cu cluster, the pore size of ZIF-67 was increased leading to more exposed Co2+ and more unsaturated coordination mental sites, which is beneficial for electrochemical oxygen evolution reaction (OER). The OER ability of pure ZIF-67 was enhanced after the introduction of Cu2 and Cu4 clusters, in which Cu4-ZIF-67 displayed the best electrochemical performance. At 10 mA cm−2, it requires an overpotential of 340 mV. The lower Tafel slope and smaller charge transfer resistance reflect its faster dynamic process. This work provides a new idea for the development of OER electrocatalysts.

The dual gain strategy of introducing nickel doping and anchoring amorphous iron oxyhydroxide nanosheets on ZIF-67 achieves an efficient oxygen evolution reaction

A ZIF-67@Ni@FeOOH composite material was synthesized using nickel-doped ZIF-67 as a precursor and was electrochemically characterized as an efficient oxygen evolution reaction (OER) catalyst. The results indicated that Ni doping preserved the polyhedral structure of ZIF-67 while enhancing its OER activity. The introduction of amorphous FeOOH nanosheets allowed ZIF-67@Ni@FeOOH to not only retain its original polyhedral structure but also develop a hollow interior and self-remodeling surface, resulting in numerous defects. These features contribute to improved charge transfer efficiency and enhanced conductivity of the material. The dual enhancement effect is achieved by combining the doping strategy with structural defect engineering. The synergistic effects of Co, Ni, and Fe species further boost OER performance. The ZIF-67@Ni@FeOOH catalyst exhibited remarkable OER efficacy, with the lowest overpotential at a current density of 10 mA cm−2 being 329 mV and a low Tafel slope of 42.95 mV dec−1. In situ Raman spectroscopy revealed that high-valence hydroxyl oxides, specifically NiOOH and CoOOH, present on the composite surface were the active species for OER. This study offers a promising approach for developing economically viable electrocatalysts with superior efficiency for OER.

Enhanced bifunctional water electrolysis performance of spherical ZnMn2O4 nanoparticles

Spinel-type transition metal oxide-based catalysts are crucial for efficient electrocatalytic oxygen and hydrogen generation. Therefore, in this study, zinc manganite (ZnMn2O4) nanostructures were synthesized using two different reducing agents, including sodium carbonate (Na2CO3) and sodium hydroxide (NaOH), through the coprecipitation method. When ZnMn2O4 was synthesized using NaOH, the sample exhibited a morphology with the aggregated and stacked nanobundles. In contrast, the Na2CO3-derived ZnMn2O4 sample demonstrated an interconnected and agglomerated spherical nanoparticle structure. For the oxygen evolution reaction, the spherical ZnMn2O4 nanoparticles exhibited the exceptional electrocatalytic performances, with an overpotential of 110 mV and a low Tafel slope of 47 mV/dec, showing excellent durability at 10 mA/cm2 in an alkaline electrolyte. For the hydrogen evolution reaction, the spherical ZnMn2O4 nanoparticles indicated a low overpotential of 158 mV and a Tafel slope of 120 mV/dec, with excellent stability at −10 mA/cm2. These findings suggest that the spherical ZnMn2O4 nanoparticles are effective electrocatalysts for highly efficient water-splitting.

Nanoarchitectonics of few-layer Ni3Fe nanosheets embedded porous nitrogen-doped carbon derived from asphalt waste: An efficient electrocatalyst for oxygen evolution reaction

The design and fabrication of stable, high-performance, and affordable oxygen evolution reaction (OER) electrocatalysts is essential for performing practical water electrolysis and generating green hydrogen energy. Here, we report that 2D few layer Ni3Fe nanosheets embedded with 2D porous nitrogen doped carbon (N-NixFe@CF) from asphalt waste and then convolved and assembled into 1D hollow nanotube structures by Lewis acid molten salt etching method, which were used as electrocatalysts for OER. Benefiting from the integrate of 1D hollow nanotube structure and 2D porous nanosheets, the close contact between catalysts and support, and the increased conductivity, the resultant N-Ni3Fe@CF catalysts exhibited high catalytic activities in the OER with low overpotential at a current density of 10 mA cm−2 (114 mV), low Tafel slope (166.6 mV dec−1), and excellent electrochemical stability. This work provides a new concept for expanding the use of asphalt wastes and by-products, as well as a straightforward synthesis method for producing economical, efficient, and long-lasting alkaline OER electrocatalysts.

Pt nanoparticles loaded on three-dimensional porous carbon as electrocatalysts for hydrogen evolution reaction

The electrochemical catalytic hydrogen evolution reaction (HER) holds significant potential for the sustainable production of environmentally friendly hydrogen energy. Currently, the precious metal Pt is widely acknowledged as the most superior electrocatalyst. However, its limited availability and exorbitant cost impede its extensive application. In this study, low Pt-loaded three-dimensional (3D) porous carbon composites were successfully synthesized as catalysts using a template-free method and a high-temperature pyrolysis method. By evaluating the HER performance of different Pt concentrations of the catalysts Pt/C-X (X=0, 0.05, 0.1, 0.2, 0.4, 0.7 mmol) in acid solution, it was observed that the overpotential of Pt/C-0.2 reached as low as 17 mV with a significantly low Tafel slope value of 48 mV cm−2. Meanwhile, the Bilayer capacitance (Cdl) reached an impressively high value of 247.5 mF cm−2. Consequently, this also provides a promising way to enhance the catalytic performance of the loaded catalysts.

Laser-induced graphene nano-anchored WS2/WO3 heterostructures for electrocatalytic oxygen evolution reaction

Tailoring surface components and nanostructures via integration of dual transition metal heteroatoms is a highly effective technique for the design and synthesis of electrocatalysts with superior performance. In this study, we report WS₂/WO₃ nanostructure enriched with sulphur and oxygen vacancies, embedded within laser-induced graphene (LIG) as carbon support, to improve alkaline and seawater splitting applications for the oxygen evolution reaction (OER). The LIG-WS₂/WO₃ nanohybrid demonstrates high OER activity and improved stability due to the synergistic interaction between LIG, WS₂, WO₃, and optimized proportion of sulphur and oxygen vacancies, which facilitates efficient charge transfer, reduces recombination losses and allows significant tuning of various electrocatalytic parameters as a function of annealing temperature. The optimized sample, LWSO@450, exhibits excellent electrocatalytic activity with a low overpotential of 350 mV at a current density of 50 mA/cm2 and an exceptionally low Tafel slope of 33 mV/decade in an alkaline medium. Moreover, the high electrochemically active surface area of 134 cm2, mass activity of 60 A/g, and turnover frequency of 0.012 s⁻1 indicate a substantial number of active sites. These findings highlight the considerable potential of this catalyst in various electrochemical domains, particularly in energy conversion, and other renewable energy systems, due to its cost-effectiveness, availability, and scalability.

Nickel-Molybdenum-Based Three-Dimensional Nanoarrays for Oxygen Evolution Reaction in Water Splitting.

Water splitting is an important approach to hydrogen production. But the efficiency of the process is always controlled by the oxygen evolution reaction process. In this study, a three-dimensional nickel-molybdenum binary nanoarray microstructure electrocatalyst is successfully synthesized. It is grown uniformly on Ni foam using a hydrothermal method. Attributed to their unique nanostructure and controllable nature, the Ni-Mo-based nanoarray samples show superior reactivity and durability in oxygen evolution reactions. The series of Ni-Mo-based electrocatalysts presents a competitive overpotential of 296 mV at 10 mA·cm-2 for an OER in 1.0 M KOH, corresponding with a low Tafel slope of 121 mV dec-1. The three-dimensional nanostructure has a large double-layer capacitance and plenty of channels for ion transfer, which demonstrates more active sites and improved charge transmission. This study provides a valuable reference for the development of non-precious catalysts for water splitting.

Phosphate-decorated hierarchical porous CoNiFe medium-entropy alloy: An efficient and low-cost electrocatalyst for seawater oxidation

The development of efficient, stable and low-cost electrocatalysts towards the seawater oxidation is highly desirable for hydrogen-based industries. In this work, we report the efficient preparation of phosphate-decorated hierarchical porous CoNiFe medium-entropy alloys as promising electrocatalysts for the oxygen evolution reaction in seawater via the solution combustion synthesis. The hierarchical porous structure of CoNiFe medium-entropy alloys enhances exposure to catalytic sites and facilitates the efficient diffusion of gas products as well as electrolytes. Moreover, the in-situ formed PO43− anions not only improve the electrocatalytic performance of CoNiFe medium-entropy alloys for oxygen evolution reaction, but also prevent Cl− from contacting the catalytic sites. Thanks to these structural benefits, the optimized CoNiFeP0.1@NF electrode demonstrates superior electrocatalytic performance for oxygen evolution reaction, showing an overpotential of 250 mV at 10 mA cm−2, a low Tafel slope of 47.6 mV dec−1, and satisfactory stability in the 1.0 M KOH +0.5 M NaCl electrolyte.

Vertical Conductive Metal-Organic Framework Single-Crystalline Nanowire Arrays for Efficient Electrocatalytic Hydrogen Evolution.

The construction of crystalline metal-organic frameworks with regular architectures supportive of enhanced mass transport and bubble diffusion is imperative for electrocatalytic applications; however, this poses a formidable challenge. Here, a method is presented that confines the growth of nano-architectures to the liquid-liquid interface. Using this method, vertically oriented single crystalline nanowire arrays of an Ag-benzenehexathiol (BHT) conductive metal-organic framework (MOF) are fabricated via an "in-plane self-limiting and out-of-plane epitaxial growth" mechanism. This material has excellent electrocatalytic features, including highly exposed active sites, intrinsically high electrical conductivity, and superhydrophilic and superaerophobic properties. Leveraging these advantages, the carefully designed material demonstrates superior electrocatalytic hydrogen evolution activity, resulting in a low Tafel slope of 66mVdec-1 and a low overpotential of 275mV at a high current density of 1Acm-2. Finite element analysis (FEA) and in situ microscopic verification indicates that the nanowire array structure significantly enhances the electrolyte transport kinetics and promotes the rapid release of gas bubbles. The findings highlight the potential of using MOF-based ordered nanoarray structures for advanced electrocatalytic applications.