Synthesis of Urchin-like Ni@NP@NCP Composites with Three Solvothermal Systems for Highly Efficient Overall Seawater Splitting

In this work, an urchin-like Ni@Ni₂P@NiCoP (Ni@NP@NCP) composite was prepared on nickel foam by a simple hydrothermal treatment process. Using the prepared NiO nanosheets as templates, the NiCo precursor was prepared in the presence of three solvothermal systems of water/dimethylformamide (DMF)/dimethyl sulfoxide (DMSO) by the hydrothermal process. After mixing and calcining with sodium hypophosphite under a nitrogen atmosphere at a high temperature for phosphating, an urchin-like Ni@NP@NCP(F/SO/H) nanostructured catalyst was obtained with superior hydrogen evolution and oxygen evolution performance. To further explore their efficiency in seawater splitting. Ni@NP@NCP(F/SO/H) composites were used as the cathode and anode of an electrolytic cell, which delivered 1.822 V potential at 300 mA cm^-2 in simulated seawater (1 M KOH and 0.5 M NaCl). This may provide an effective way of developing clean energy.

2D Metal-Organic Frameworks as Competent Electrocatalysts for Water Splitting

Hydrogen, a clean and flexible energy carrier, can be efficiently produced by electrocatalytic water splitting. To accelerate the sluggish hydrogen evolution reaction and oxygen evolution reaction kinetics in the splitting process, highly active electrocatalysts are essential for lowering the energy barriers, thereby improving the efficiency of overall water splitting. Combining the distinctive advantages of metal-organic frameworks (MOFs) with the physicochemical properties of 2D materials such as large surface area, tunable structure, accessible active sites, and enhanced conductivity, 2D MOFs have attracted intensive attention in the field of electrocatalysis. Different strategies, such as improving the conductivities of MOFs, reducing the thicknesses of MOF nanosheets, and integrating MOFs with conductive particles or substrates, are developed to promote the catalytic performances of pristine MOFs. This review summarizes the recent advances of pristine 2D MOF-based electrocatalysts for water electrolysis. In particular, their intrinsic electrocatalytic properties are detailly analyzed to reveal important roles of inherent MOF active centers, or other in situ generated active phases from MOFs responsible for the catalytic reactions. Finally, the challenges and development prospects of pristine 2D MOFs for the future applications in overall water splitting are discussed.

Metal-organic frameworks-derived layered double hydroxides: From controllable synthesis to various electrochemical energy storage/conversion applications

Over the past years, metal-organic frameworks (MOF) have been directly used as electrodes or as a precursor for MOF-derived materials in energy storage and conversion systems. In the wide range of existing MOF derivatives, MOF-derived layered double hydroxides (LDHs) are determined to be promising materials due to their unique structure and features. However, MOF-derived LDHs (MDL) materials can suffer from insufficient intrinsic conductivity and agglomeration during formation. Various techniques and approaches were designed and applied to tackle these problems, such as using ternary LDHs, ion-doping, sulphurization, phosphorylation, selenization, direct growth, and conductive substrates. All the mentioned enhancement techniques aim to create the ideal electrode materials with maximum performance. In this review, we gathered and discussed the most recent progressive advances, different synthesis methodologies, unsolved challenges, applications, and electrochemical and electrocatalytic performance of MDL materials. We hope this work will be a reliable source for future progress and synthesis of these materials.

Self-Supporting Metal-Organic Framework-Based Nanoarrays for Electrocatalysis

The replacement of powdery catalysts with self-supporting alternatives for catalyzing various electrochemical reactions is extremely important for the large-scale commercial application of renewable energy storage and conversion technologies. Metal-organic framework (MOF)-based nanoarrays possess tunable compositions, well-defined structure, abundant active sites, effective mass and electron transport, etc., which enable them to exhibit superior electrocatalytic performance in multiple electrochemical reactions. This review presents the latest research progress in developing MOF-based nanoarrays for electrocatalysis. We first highlight the structural features and electrocatalytic advantages of MOF-based nanoarrays, followed by a detailed summary of the design and synthesis strategies of MOF-based nanoarrays, and then describe the recent progress of their application in various electrocatalytic reactions. Finally, the challenges and perspectives are discussed, where further exploration into MOF-based nanoarrays will facilitate the development of electrochemical energy conversion technologies.

Hierarchical CoMoS3.13/MoS2 hollow nanosheet arrays as bifunctional electrocatalysts for overall water splitting

Hollow hetero-nanosheet arrays have attracted great attention due to their efficient catalytic abilities for water splitting. We successfully fabricated ZIF-67-derived hollow CoMoS_3.13/MoS₂ nanosheet arrays on carbon cloth in situ through a two-step heating-up hydrothermal method, in which the MoS₂ nanosheets were suitably distributed on the surface of the hollow CoMoS_3.13 nanosheet arrays. There was a distinct synergistic effect between CoMoS_3.13 and MoS₂, and a large number of defective and disordered interfaces were formed, which improved the charge transfer rate and provided abundant electrochemical active sites. CMM 0.5, with the optimal Mo doping concentration of 0.5 mmol, exhibited the best catalytic properties. The overpotential values of CMM 0.5 at 10 mA cm^-2 were only 107 and 169 mV for the HER and OER, respectively, and it had nearly 100% faradaic efficiency. A dual-electrode electrolytic cell assembled with CMM 0.5 required a voltage of only 1.507 V at 10 mA cm^-2 for overall water splitting, and it displayed remarkable long-term durable bifunctional stability.

Critical Review, Recent Updates on Zeolitic Imidazolate Framework-67 (ZIF-67) and Its Derivatives for Electrochemical Water Splitting

Design and construction of low-cost electrocatalysts with high catalytic activity and long-term stability is a challenging task in the field of catalysis. Metal-organic frameworks (MOF) are promising candidates as precursor materials in the development of highly efficient electrocatalysts for energy conversion and storage applications. This review starts with a summary of basic concepts and key evaluation parameters involved in the electrochemical water-splitting reaction. Then, different synthesis approaches reported for the cobalt-based Zeolitic imidazolate framework (ZIF-67) and its derivatives are critically reviewed. Additionally, several strategies employed to enhance the electrocatalytic activity and stability of ZIF-67-based electrocatalysts are discussed in detail. The present review provides a succinct insight into the ZIF-67 and its derivatives (oxides, hydroxides, sulfides, selenides, phosphide, nitrides, telluride, heteroatom/metal-doped carbon, noble metal-supported ZIF-67 derivatives) reported for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting applications. Finally, this review concludes with the associated challenges and the perspectives on developing the best economic, durable electrocatalytic materials.

A CoNi telluride heterostructure supported on Ni foam as an efficient electrocatalyst for the oxygen evolution reaction

The excellent oxygen evolution reaction performance of a CoNi telluride heterostructure (0.4CoNi LDH@Te-180C) can be attributed to the inherent layered structure, interconnected nanoarray structures and the synergistic effect of Co and Ni species.

Construction of high-performance electrode materials of NiCo2O4 nanoparticles encapsulated in ultrathin N-doped carbon nanosheets for supercapacitors

Highly dispersed nitrogen doped carbon (N-C) is decomposed by 2-methylimidazole (C₄H₆N₂) and is used as a composite material with nickel cobaltite (NiCo₂O₄). The N-C and NiCo₂O₄ composites are obtained by a one-step hydrothermal method and subsequent calcination. In addition, N-C is used to control the morphology and structure of NiCo₂O₄ to obtain excellent capacitor materials. The N-C/NiCo₂O₄ electrode shows an excellent specific capacitance of 157.97 mA h g^-1 (1263.75 F g^-1) at 1 A g^-1. Herein, we successfully develop a N-C/NiCo₂O₄//AC asymmetric supercapacitor (ASC), which is prepared using N-C/NiCo₂O₄ as a cathode coupled with activated carbon (AC) as an anode at a voltage of 1.6 V. The prepared N-C/NiCo₂O₄//AC device shows an excellent volumetric energy density of 66.44 mW h kg^-1. The promising performance of N-C/NiCo₂O₄//AC illustrated its potential for portable supercapacitor applications.

Self-supported cobalt–nickel bimetallic telluride as an advanced catalyst for the oxygen evolution reaction

The Ni-doped Co@CoTe2 electrode exhibits an outstanding OER activity and excellent long-term stability and outperforms most of the well-studied Co-based dichalcogenides.

2D Bismuth nanosheet arrays as efficient alkaline hydrogen evolution electrocatalysts

Bismuth nanosheets were prepared using ethylene glycol, which exhibit low overpotential and show great potential in the field of hydrogen evolution reaction.