Water splitting driven by renewable energy sources is considered a sustainable way of hydrogen production, an ideal fuel to overcome the energy issue and its environmental challenges. The rational design of electrocatalysts serves as a critical point to achieve efficient water splitting. Layered double hydroxides (LDHs) with two-dimensionally (2D) layered structures hold great potential in electrocatalysis owing to their ease of preparation, structural flexibility, and tenability. However, their application in catalysis is limited due to their low activity attributed to structural stacking with irrational electronic structures, and their sluggish mass transfers. To overcome this challenge, attempts have been made toward adjusting the morphological and electronic structure using appropriate design strategies. This review highlights the current progress made on design strategies of transition metal-based LDHs (TM-LDHs) and their application as novel catalysts for oxygen evolution reactions (OERs) in alkaline conditions. We describe various strategies employed to regulate the electronic structure and composition of TM-LDHs and we discuss their influence on OER performance. Finally, significant challenges and potential research directions are put forward to promote the possible future development of these novel TM-LDHs catalysts.

Ni-based electrocatalysts, especially with Fe, are attractive electrocatalysts for oxygen evolution reaction (OER) due to their exhilarating surface properties and anticipated synergistic effect. Herein, amorphous Ni1–x Fe x oxyhydroxide nanosheets (x: 0, 0.25, 0.50, 0.75, and 1) with integrated bulk and surface Fe were synthesized by facile electrodeposition as an active and stable electrocatalyst for OER. Different ratios of Fe and Ni precursors were deposited on nickel foam cathodically for bulk Fe (FeB) embodiment. Then, surface Fe (FeS) was integrated through anodic cycling from Fe-containing KOH. Benefiting from the amorphous structure and integration between FeB and FeS, high activity and stability were achieved. Accordingly, FeB+S-NIFE25 has demonstrated the highest OER activity, with the lowest overpotential of 300 mV at a current density of 50 mA cm–2, a Tafel slope as low as 30 mV dec–1, and robust stability exceeding 100 h for continuous oxygen generation while the same material (NIFE25) in the absence of FeS, has demonstrated relatively a higher overpotential of 340 mV and a Tafel slope of 65 mV dec–1. Computation simulation also calculated that the NIFEX composites containing both FeB and FeS demonstrated weak binding energies enhancing OH– density at the reaction interface facilitating O2 generation. It is probable that the synergy between FeB and FeS coupled with an amorphous structure induces higher OER activity and stability and can be readily applied to generate cheap and clean hydrogen energy.

Decarbonization of the global energy system requires a coordinated effort towards disruptive technology of renewable energy conversion and storage (ECS) that can be potential to secure and diversify energy systems by increasing efficiency of conversion and storage of intermittent energy sources. Porous nanostructures have been newly reported as a promising class of most effective materials for this purpose because of their unique advantages in terms of large surface‐to‐volume ratios, surface permeability, and void spaces. These offer abundant active sites for ultimate electrochemical activities by the shortening pathway of mass/charge transport. Particularly, Fe‐based mesoporous nanostructures (mp‐FeNSs) have been recently fascinating. Iron is a principal active center in nanocomposites and has high industrial suitability for next‐generation technology owing to its environment friendliness, abundance, and low cost. In this review, crucial technical advances related to mp‐FeNSs that have occurred during 2016–2020 are summarized in terms of synthesis, structural design strategy, and ECS applications such as water electrocatalysis, Li‐ion batteries, and supercapacitors. This review is supportive for potential readers to obtain general and professional information in this field since Fe‐based energy materials are exclusively introduced in the article including a fundamental understanding of electrochemistry and related technologies in detail.

Hydrogen produced by electrochemical water splitting is considered a sustainable fuel source, an ideal way to solve the energy problem and its environmental challenges. However, industrial production of hydrogen from...

A feasible nanoscale framework of heterogeneous plasmonic materials and proper surface engineering can enhance photoelectrochemical (PEC) water‐splitting performance owing to increased light absorbance, efficient bulk carrier transport, and interfacial charge transfer. This article introduces a new magnetoplasmonic (MagPlas) Ni‐doped Au@FexOy nanorods (NRs) based material as a novel photoanode for PEC water‐splitting. A two stage procedure produces core–shell Ni/Au@FexOy MagPlas NRs. The first‐step is a one‐pot solvothermal synthesis of Au@FexOy. The hollow FexOy nanotubes (NTs) are a hybrid of Fe2O3 and Fe3O4, and the second‐step is a sequential hydrothermal treatment for Ni doping. Then, a transverse magnetic field‐induced assembly is adopted to decorate Ni/Au@FexOy on FTO glass to be an artificially roughened morphologic surface called a rugged forest, allowing more light absorption and active electrochemical sites. Then, to characterize its optical and surface properties, COMSOL Multiphysics simulations are carried out. The core–shell Ni/Au@FexOy MagPlas NRs increase photoanode interface charge transfer to 2.73 mAcm−2 at 1.23 V RHE. This improvement is made possible by the rugged morphology of the NRs, which provide more active sites and oxygen vacancies as the hole transfer medium. The recent finding may provide light on plasmonic photocatalytic hybrids and surface morphology for effective PEC photoanodes.

Porous core−shell nanoparticles (NPs) have emerged as a promising material for broad ranges of applications in catalysts, material chemistry, biology, and optical sensors. Using a typical Ag core−Fe 3 O 4 shell NP, a.k.a., magnetoplasmonic (MagPlas) NP, two porous shell models were prepared: i.e., Ag@Fe 3 O 4 NPs and its SiO 2 -covered NPs (Ag@Fe 3 O 4 @SiO 2 ). We suggested using cyclic voltammetry (CV) to provide unprecedented insight into the porosity of the core− shell NPs caused by the applied potential, resulting in the selective redox activities of the core and porous shell components of Ag@Fe 3 O 4 NPs and Ag@Fe 3 O 4 @SiO 2 NPs at different cycles of CV. The porous and nonporous core−shell nanostructures were qualitatively and quantitatively determined by the electrochemical method. The ratio of the oxidation current peak (μA) of Ag to Ag + in the porous shell to that in the SiO 2 coated (nonporous) shell was 400:3.2. The suggested approach and theoretical background could be extended to other types of multicomponent NP complexes.

Transition metal based layered double hydroxides (TMLDHs) are potential candidates for supercapacitors; however, their structural staking often limits their energy density, one of the major pending obstacles in the sector. Simple, fast, and safe modification strategies such as exfoliation of jammed layers into single sheets can be a viable option to overcome those challenges. This work reports fabrication of an ultrathin nanosheets from bulk TMLDHs using superficial non-thermal Arplasma exfoliation strategy. Electrochemical characterizations have confirmed that capacitive performance of pristine NiCoO x nanosheets has improved because of Ar-plasma induced exfoliation. A remarkable of 5.7 F cm À 2 areal capacitance was achieved at a current density of 5 mA cm À 2 for ultrathin Ar-NiCoO x nanosheets. The material also exhibited excellent cyclic stability with over 88 % capacitance retention after 5000 cycles. The electrode material assembled into symmetric supercapacitor device delivering an energy density of 85.9 μWh cm À 2 at a power density of 500 μW cm À 2 .The higher supercapacitive performance is attributed to increased electrochemical surface area and improved capability of electron and ion transport induced by Ar-plasma exfoliation, demonstrating an opportunity for further use of TMLDHs in the energy conversion and storage sector.

The Cover Feature illustrates a Fe‐based mesoporous nanostructure (located at the center) and its applications in electrochemical energy conversion (water splitting) and various electrochemical energy storage devices (Li‐ion batteries and supercapacitors). More information can be found in the Review by J. Lee and co‐workers.