Institute of Fundamental Technological Research

A promising approach to catalysis in various electrochemical applications is engineering of heterostructures with enhanced active sites and interfacial electron transfer processes. In this study, conductive NiCo2S4 was interfaced with layered MoS2 as bifunctional electrode material for asymmetric supercapacitors and hydrogen generation through water splitting. The creation of opposite charges within the heterostructure components facilitates the adsorption of OH− and H+ ions, thereby boosting the bifunctional potentials. The constructed NiCo2S4/MoS2 electrode showed excellent specific capacitance of 1488.9 F g−1 at 1.0 A g−1 current density and capacity retention of 93 % after 30-fold rise in current density. The asymmetric supercapacitor exhibits superior energy density of 63 Wh kg−1 at power density 7.56 kW kg−1 compared to similar electrode materials reported in literature. The hydrogen evolution performance of the electrode materials in alkaline media produced a low overpotential (79.95 mV at 10 mA cm−2) and small Tafel slope (59 mV dec−1) that are comparable to the state-of-the-art Pt/C. Density functional theory calculation reveals a fast electron transfer from NiCo2S4 to MoS2 leading to creation of positively charged surface and negatively charged surface at NiCo2S4 and MoS2 respectively that facilitate the adsorption of OH− and H+ ions. This study offered a promising high active and stable non platinum advanced electrode bifunctional catalyst for energy storage supercapacitor and energy conversion hydrogen generation.

Heterostructure, NiCo2S4, MoS2, Supercapacitor, HER

The anodic substitution of a sluggish oxygen evolution reaction with a more energy-saving hydrazine oxidation reaction has the potential to greatly reduce energy consumption for hydrogen production. However, the underlying mechanism of the hydrazine oxidation reaction remains ambiguous, and the existing hydrazine splitting generally requires an external power source to drive the anodic and cathodic reactions, which is not suitable for outdoor applications. In this study, we have developed a heterostructure sulfide-based catalyst that effectively catalyzes both hydrazine oxidation and hydrogen evolution reactions. Through in situ Raman spectroscopy, we have confirmed that the breakage of the nitrogen-nitrogen single bond is a pathway for the hydrazine oxidation reaction. The enhanced electrocatalytic performance is attributed to the increased active sites and accelerated electron transfer within the heterostructures, which reduced the energy barrier, thereby enabling the fabricated electrolyzer using the g-C3N4/Ni(CN)2@NiS catalyst to deliver 200 mA cm−2 with a low voltage of 0.31 V. The assembled electrolyzer can be powered by a g-C3N4/Ni(CN)2@NiS anode-equipped direct hydrazine fuel cell, achieving self-powered hydrogen production with faradaic efficiency of more than 97 %.

Functional electrod, Carbon nitride, Hydrogen generation, Hydrazine

For the development of the next generation of portable energy storage devices, compression tolerant electrodes are essential, but most of previous reports focused only on carbon-based materials. Herein, gelatin methacrylate (GelMA) and poly(N-isopropylacrylamide) (PNIIPAM) were used as host to incorporate Co3O4@MoS2 Aerogel (Co3O4@MoS2 AG). The GelMa-PNIPAM (GP) was transformed into carbon network as an intrinsically compressible host template with high conductivity. The as-prepared electrode possesses a reversible compressive strain of 80% with excellent durability. Density functional theory (DFT) calculations show that the Co3O4@MoS2-AG heterostructure exhibits high electronic conductivity, low adsorption energy for OH- ions and fast electron transfer capacity, which enhance the electrochemical performance with high specific capacitance of 1026.9 at 1 A g-1 with remarkable cycling stability of 80.8% after 10,000 charge-discharge cycles. Besides, the assembled asymmetric supercapacitor based on compressible Co3O4@MoS2 AG/RGO exhibits stable energy storage performance under different compressive strains and after 100 compression-release cycles. The results of this study demonstrate the potential of metal-based electrode with high energy storage properties for wearable devices.

Compressible electrode, Assymetric supercapacitor, Aerogel, CO3O4, MoS2

The urea oxidation reaction (UOR) is characterized by a lower overpotential compared to the oxygen evolution reaction (OER) during electrolysis, which facilitates the hydrogen evolution reaction (HER) at the cathode. Charge
distribution, which can be modulated by the introduction of a heterostructure, plays a key role in enhancing the adsorption and cleavage of chemical groups within urea molecules. Herein, a facile all-room temperature synthesis of functional heterojunction NiCo2 S4 /CoMo 2 S4 grown on carbon cloth (CC) is presented, and the as-prepared electrode served as a catalyst for simultaneous hydrogen evolution and urea oxidation reaction. The Density
Functional Theory (DFT) study reveals spontaneous transfer of charge at the heterointerface of NiCo 2 S4 /CoMo 2 S4 , which triggers the formation of localized electrophilic/nucleophilic regions and facilitates the adsorption of electron donating/electron withdrawing group in urea molecules during the UOR. The NiCo2 S4 /CoMo 2 S4 // NiCo 2 S4 /CoMo 2 S4 electrode pair required only a cell voltage of 1.17 and 1.18 V to deliver a current density of 10 and 100 mA cm−2 respectively in urea electrolysis cell and display very good stability. Tests performed in real urine samples show similar catalytic performance to urea electrolytes, making the work one of the best transition
metal-based catalysts for UOR applications, promising both efficient hydrogen production and urea decomposition.

Hydrazine oxidation (HzOR) assisted hydrogen production offers a promising
alternative to energy-intensive and sluggish oxygen evolution reaction (OER),
improving its efficiency. However, its practical implementation demands
the development of advanced electrocatalysts capable of overcoming intrinsic
kinetic and charge transfer limitations. Herein, the study reports a hybrid catalyst by anchoring a

Hydrazine oxidation, Hydrogen evolution, Covalent organic framework, interfacial interaction

Catalyst design plays a critical role in ensuring sustainable andeffective energy conversion. Electrocatalytic materials need tobe able to control active sites and introduce defects in bothacidic and alkaline electrolytes. Furthermore, producing efficientcatalysts with a distinct surface structure advances ourcomprehension of the mechanism. Here, a defect-engineeredheterointerface of ruthenium doped cobalt metal organic frame(Ru-CoMOF) core confined in MoS2 is reported. A tailored designapproach at room temperature was used to induce defects andform an electron transfer interface that enhanced the electro-catalytic performance. The Ru-CoMOF@MoS2 heterointerfaceobtains a geometrical current density of 10 mA-2 by providinghydrogen evolution reaction (HER) and oxygen evolutionreaction (OER) at small overpotentials of 240 and 289 mV,respectively. Density functional theory simulation shows thatthe Co-site maximizes the evolution of hydrogen intermediateenergy for adsorption and enhances HER, while the Ru-site, onthe other hand, is where OER happens. The heterointerfaceprovides a channel for electron transfer and promotes reactionsat the solid-liquid interface. The Ru-CoMOF@MoS2 modelexhibits improved OER and HER efficiency, indicating that itcould be a valuable material for the production of water-alkaline and acidic catalysts

Copper nanoparticles (CuNPs) have garnered significant attention in biomedicine due to their various properties and potential applications. These nanoparticles exhibit promising antimicrobial, anticancer, and antioxidant activities, which enhance their value in nanomedicine applications. Their properties, shaped by the fabrication techniques, facilitate their application in drug delivery, cancer therapy, tissue engineering, and dental applications uses. Nevertheless, obstacles persist in attaining biocompatibility and regulated release, which are vital for effective clinical transference. Toxicological evaluations are essential to ensure the secure utilization of CuNPs. Additionally, studies are ongoing to find creative solutions to address these challenges and fully harness the medical potential of CuNPs.

Copper nanoparticles,Antibacterial,Synthesis,Biocompatibility,Biomedical applications

The major hindrance to efficient electrocatalytic hydrogen generation from water electrolysis is the sluggish kinetics with corresponding large overvoltage of oxygen evolution reaction. Herein, we report a defective 2D NiCoMoS@Ni(CN)2 core-shell heterostructure derived from Hofmann-type MOF as an efficient and durable high-performance noble metal-free electrocatalyst for hydrazine oxidation reaction (HzOR) in alkaline media. The sluggish oxygen evolution reaction was replaced with a more thermodynamically favourable HzOR, enabling energy-saving electrochemical hydrogen production with 2D NiCoMoS@Ni(CN)2 acting as a bifunctional electrocatalyst for anodic HzOR and cathodic hydrogen generation. Operating at room temperature, the two-electrode electrolyzer delivers 100 mA cm−2 from a cell voltage of just 257 mV, with strong long-term electrochemical durability and nearly 100% Faradaic efficiency for hydrogen evolution in 1.0 M KOH aqueous solution with 0.5 M hydrazine. The density functional theory (DFT) was employed to investigate the origin of catalytic performance and showed that high vacancy creation within the heterointerface endowed NiCoMoS@Ni(CN)2 with favourable functionalities for excellent catalytic performance.

Defect engineering, Core-shell, Electrocatalyst, Hydrazine oxidation, Heterostructure