One-step hydrothermal synthesis of a Ni3S2-FeMoO4 nanowire-nanosheet heterostructure array for synergistically boosted oxygen evolution reaction

A key factor for boosting oxygen evolution reaction (OER) is the design of heterostructures with steerable defects and interfaces, which can optimize the surface electronic structures and achieve efficient water splitting to produce hydrogen fuel. Herein, we propose a novel one-step hydrothermal approach to fabricate hierarchical Ni3S2 nanowires with an S-doped FeMoO4 nanosheet heterostructure array in situ on Ni-Fe foam (NFF) as a self-standing electrode for synergistically boosted OER. The metalloid Ni3S2 nanowires with good conductivity support the FeMoO4 nanosheets and act as high-speed paths for the charge transfer. Numerous ultrathin S-doped FeMoO4 nanosheets are uniformly distributed on each Ni3S2 nanowire to form heterostructures with larger specific surface area and more revealable active sites, and a strong synergistic effect is created at the heterostructure interfaces to further promote the OER dynamics. Additionally, the NFF serves as the conductive support substrate and simultaneously provides the Ni and Fe sources for the self-growing Ni3S2-FeMoO4, leading to a structurally-integrated electrode with low contact resistance, fast mass transfer, and good stability. Therefore, the Ni3S2-FeMoO4/NFF electrode offers a low overpotential of 331 mV to achieve 500 mA cm-2 and long-term stability at 100 mA cm-2 level for more than 40 h. This work provides insight into the heterostructure of molybdate and sulfide, and a deep understanding of the significance of the synergism in OER operation.

A Coordination-Derived Cerium-Based Amorphous-Crystalline Heterostructure with High Electrocatalytic Oxygen Evolution Activity

The rational design of heterogeneous catalysts is crucial for achieving optimal physicochemical properties and high electrochemical activity. However, the development of new amorphous-crystalline heterostructures is significantly more challenging than that of the existing crystalline-crystalline heterostructures. To overcome these issues, a coordination-assisted strategy that can help fabricate an amorphous NiO/crystalline NiCeOx (a-NiO/c-NiCeOx ) heterostructure is reported herein. The coordination geometry of the organic ligands plays a pivotal role in permitting the formation of coordination polymers with high Ni contents. This consequently provides an opportunity for enabling the supersaturation of Ni in the NiCeOx structure during annealing, leading to the endogenous spillover of Ni from the depths of NiCeOx to its surface. The resulting heterostructure, featuring strongly coupled amorphous NiO and crystalline NiCeOx , exhibits harmonious interactions in addition to low overpotentials and high catalytic stability in the oxygen evolution reaction (OER). Theoretical calculations prove that the amorphous-crystalline interfaces facilitate charge transfer, which plays a critical role in regulating the local electron density of the Ni sites, thereby promoting the adsorption of oxygen-based intermediates on the Ni sites and lowering the dissociation-related energy barriers. Overall, this study underscores the potential of coordinating different metal ions at the molecular level to advance amorphous-crystalline heterostructure design.

Crystalline/Amorphous Mo-Ni(OH)2/FexNiy(OH)3x+2y hierarchical nanotubes as efficient electrocatalyst for overall water splitting

The development of efficient bifunctional catalysts for overall water splitting is highly desirable and essential for the advancement of hydrogen technology. In this work, Mo-Ni(OH)2/FexNiy(OH)3x+2y with hierarchical nanotube structure is constructed on flexible carbon cloth (CC) through simple electrochemical deposition and hydrothermal method. The hollow tube-structure is in favor of both exposing active sites and enhancing mass transfer capability. Moreover, the doping of Mo can enhance the electronic conductivity of heterostructures. The interfacial interaction between amorphous and crystal can enhance effectively the charge transfer kinetics across the interface. Therefore, Mo-Ni(OH)2/FexNiy(OH)3x+2y can achieve a low overpotential of 57 mV for hydrogen evolution reaction (HER) and 229 mV for oxygen evolution reaction (OER) at 10 mA·cm-2. In addition, Mo-Ni(OH)2/FexNiy(OH)3x+2y needs a potential of only 1.54 V at 10 mA·cm-2 for overall water splitting, and retains for a long period of time (60 h) reliable. The work will provide a valuable approach to the construction of highly efficient electrocatalysts for overall water splitting.

2D/2D heterostructure Ni-Fe LDH/black phosphorus nanosheets with AuNP for noxious substance diphenylamine detection in food samples

In this study, gold nanoparticles decorated on nickel-iron layered double hydroxide with black phosphorus nanosheets (AuNP/Ni-Fe LDH/BPNSs) composite were prepared using a stirring method. Analyte tracing is required for developing viable sensors. The AuNP/Ni-Fe LDH/BPNSs composite exhibited a large specific surface area, high conductivity, high electrocatalytic activity, and rapid electron transfer. These properties play a vital role in monitoring diphenylamine (DPA) in food samples. The formation of the AuNP/Ni-Fe LDH/BPNSs composite was confirmed using various structural and morphological characterization techniques. The electroanalytical character of the AuNP/Ni-Fe LDH/BPNSs composite was evaluated using voltammetry. Interestingly, the AuNP/Ni-Fe LDH/BPNSs showed a wide linear range of 0.0125-1003.82 μM and a detection limit of 4.63 nM with a sensitivity of 0.399 µA µM-1 cm-2. The constructed sensor shows considerable selectivity, stability, repeatability, and reproducibility, and the practicability of DPA was monitored in the apples, sweet tomatoes, pears, and grapes with satisfactory recoveries.

Fabrication of a hierarchical NiTe@NiFe-LDH core-shell array for high-efficiency alkaline seawater oxidation

Herein, a hierarchical NiTe@NiFe-LDH core-shell array on Ni foam (NiTe@NiFe-LDH/NF) demonstrates its effectiveness for oxygen evolution reaction (OER) in alkaline seawater electrolyte. This NiTe@NiFe-LDH/NF array showcases remarkably low overpotentials of 277 mV and 359 mV for achieving current densities of 100 and 500 mA cm-2, respectively. Also, it shows a low Tafel slope of 68.66 mV dec-1. Notably, the electrocatalyst maintains robust stability over continuous electrolysis for at least 50 h at 100 mA cm-2. The remarkable performance and hierarchical structure advantages of NiTe@NiFe-LDH/NF offer innovative insights for designing efficient seawater oxidation electrocatalysts.

Electron-Redistributed NiCo@NiFe-LDH Core-Shell Heterostructure for Significantly Enhancing Electrochemical Water Splitting

Layered double hydroxides (LDHs) are some of the most promising precursors for the development of economically stable and efficient electrocatalysts for water splitting. An effective strategy for designing excellent performance electrocatalysts is to assemble core-shell heterostructures with a tunable electronic structure. In this work, three core-shell heterostructure electrocatalysts (NiCo@NiFe-LDH100/150/200) are developed by a simple hydrothermal and subsequent electrodeposition method on Ni foam. Among them, NiCo@NiFe-LDH150/NF exhibits the best oxygen evolution reaction electrocatalytic activity and long-term stability with a low overpotential of 197 mV to deliver a current density of 10 mA cm-2. In addition, an efficient and stable alkaline electrolytic cell with NiCo@NiFe-LDH150/NF both as the cathode and anode achieves a voltage of 1.66 V at a current density of 10 mA cm-2 and realization of ultralong stability at current densities of 20 and 200 mA cm-2 for 200 h. Density functional theory calculations reveal the strong electron interaction at the heterogeneous interface of the NiCo@NiFe-LDH150/NF core-shell structure, which effectively improves the intrinsic electron conductivity and ion diffusion kinetics and makes an important contribution to the electrocatalytic performance of the material. This work provides a new idea for the selection of materials for electrochemical water splitting by the construction of heterojunction interfaces.

Research Advances in Amorphous-Crystalline Heterostructures Toward Efficient Electrochemical Applications

Interface engineering of heterostructures has proven a promising strategy to effectively modulate their physicochemical properties and further improve the electrochemical performance for various applications. In this context related research of the newly proposed amorphous-crystalline heterostructures have lately surged since they combine the superior advantages of amorphous- and crystalline-phase structures, showing unusual atomic arrangements in heterointerfaces. Nonetheless, there has been much less efforts in systematic analysis and summary of the amorphous-crystalline heterostructures to examine their complicated interfacial interactions and elusory active sites. The critical structure-activity correlation and electrocatalytic mechanism remain rather elusive. In this review, the recent advances of amorphous-crystalline heterostructures in electrochemical energy conversion and storage fields are amply discussed and presented, along with remarks on the challenges and perspectives. Initially, the fundamental characteristics of amorphous-crystalline heterostructures are introduced to provide scientific viewpoints for structural understanding. Subsequently, the superiorities and current achievements of amorphous-crystalline heterostructures as highly efficient electrocatalysts/electrodes for hydrogen evolution reaction, oxygen evolution reaction, supercapacitor, lithium-ion battery, and lithium-sulfur battery applications are elaborated. At the end of this review, future outlooks and opportunities on amorphous-crystalline heterostructures are also put forward to promote their further development and application in the field of clean energy.