In this work, 2D g-C 3 N 4 nanosheets were employed as a sensitive interface for high-performance NO 2 SAW gas sensors, operating at various environmental conditions. The immense sensitivity to NO 2 gas is attributed to the enhanced mass loading effect. 

Highly sensitive g-C3N4 nanosheets as a potential candidate for the effective detection of NO2 gas via langasite-based surface acoustic wave gas sensor

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.

https://www.mdpi.com/2079-4991/11/6/1388/pdf

Transition Metal-Based 2D Layered Double Hydroxide Nanosheets: Design Strategies and Applications in Oxygen Evolution Reaction

Seawater splitting represents an inexpensive and attractive route for producing hydrogen, which does not require a desalination process. Highly active and durable electrocatalysts are required to sustain seawater splitting. Herein we report the phosphidation-based synthesis of a cobalt–iron–phosphate ((Co,Fe)PO4) electrocatalyst for hydrogen evolution reaction (HER) toward alkaline seawater splitting. (Co,Fe)PO4 demonstrates high HER activity and durability in alkaline natural seawater (1 M KOH + seawater), delivering a current density of 10 mA/cm2 at an overpotential of 137 mV. Furthermore, the measured potential of the electrocatalyst ((Co,Fe)PO4) at a constant current density of −100 mA/cm2 remains very stable without noticeable degradation for 72 h during the continuous operation in alkaline natural seawater, demonstrating its suitability for seawater applications. Furthermore, an alkaline seawater electrolyzer employing the non-precious-metal catalysts demonstrates better performance (1.625 V at 10 mA/cm2) than one employing precious metal ones (1.653 V at 10 mA/cm2). The non-precious-metal-based alkaline seawater electrolyzer exhibits a high solar-to-hydrogen (STH) efficiency (12.8%) in a commercial silicon solar cell.

Cobalt–Iron–Phosphate Hydrogen Evolution Reaction Electrocatalyst for Solar-Driven Alkaline Seawater Electrolyzer

Amorphous Ni1–xFex Oxyhydroxide Nanosheets with Integrated Bulk and Surface Iron for a High and Stable Oxygen Evolution Reaction

Reasonable optimization of the crystal structure and composite is an effective way to enhance the electrocatalytic activity of transition metal oxides. Herein, we report a strategy to fabricate Fe-doped amorphous CoOx (a-CoyFezOx) as an oxygen evolution reaction (OER) catalyst by a facile reduction reaction at room temperature. In a 1 M KOH electrolyte, the optimized a-Co2.5Fe0.5Ox catalyst shows the best OER activity. It only requires a 280 mV overpotential to achieve a current density of 10 mA cm–2 with a Tafel slope of 39.9 mV dec–1, which is even better than that of a commercial IrO2 catalyst. This high activity can be ascribed to the combined merits of the amorphous structure and the doped Fe element. The amorphous structure can enlarge the electrochemically accessible surface area and offer more active sites, while the Fe doped into the amorphous CoOx material can not only form the Fe site to promote the adsorption of intermediates during the OER process but also optimize the electronic structure of neighboring Co sites to enhance the OER activity. This work provides a strategy for rational design and large-scale synthesis of the transition metal oxide electrocatalysts to enhance the OER performance. 

Large-Scale Synthesis of Fe-Doped Amorphous Cobalt Oxide Electrocatalysts at Room Temperature for the Oxygen Evolution Reaction

Fe-Based Mesoporous Nanostructures for Electrochemical Conversion and Storage of Energy

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...

Ni-Based Ultrathin Nanostructures for Overall Electrochemical Water Splitting

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 Ar-plasma exfoliation strategy. Electrochemical characterizations have confirmed that capacitive performance of pristine NiCoOx nanosheets has improved because of Ar-plasma induced exfoliation. A remarkable of 5.7 F cm−2 areal capacitance was achieved at a current density of 5 mA cm−2 for ultrathin Ar-NiCoOx 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−2 at a power density of 500 μW cm−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. 

Birhanu Bayissa Gicha

Papers

Transition Metal-Based 2D Layered Double Hydroxide Nanosheets: Design Strategies and Applications in Oxygen Evolution Reaction

Fe-Based Mesoporous Nanostructures for Electrochemical Conversion and Storage of Energy

Amorphous Ni1–xFex Oxyhydroxide Nanosheets with Integrated Bulk and Surface Iron for a High and Stable Oxygen Evolution Reaction

Ni-Based Ultrathin Nanostructures for Overall Electrochemical Water Splitting

Non‐Thermal Plasma Assisted Fabrication of Ultrathin NiCoOx Nanosheets for High‐performance Supercapacitor