Instytut Podstawowych Problemów Techniki

Streszczenie:

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.

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Streszczenie:

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

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Streszczenie:

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.

Słowa kluczowe:

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

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