Defect-rich Fe-doped NiS/MoS2 heterostructured ultrathin nanosheets for efficient overall water splitting

Recent Progress in Catalysis Using High-Entropy Metal-Organic Frameworks and their Derived Materials

High-entropy metal-organic framework (HE-MOF) and their derived materials are a novel class of multipurpose materials with enormous catalytic potential. By incorporating multiple metal sites into a single MOF structure, HE-MOFs offer tunable electronic structures, diverse active sites, and enhanced stability-key attributes for catalytic applications. This review article presents a complete examination of current progress in HE-MOFs and their derived materials for diverse catalytic reactions, including electrocatalysis, photocatalysis, and thermal catalysis. Various strategies for boosting the catalytic reactivity of HE-MOFs and their derived materials have been discussed, including pore architecture modulation, morphological control, defect engineering, elemental composition tuning, and interface optimization. A thorough investigation has been conducted on various catalytic reactions like water splitting, oxygen reduction, nitrogen reduction, alcohol oxidation, hydrogenation, and cycloaddition. Furthermore, the underlying structure-property correlation governing their activity has been discussed, and key challenges and future directions in this rapidly evolving field have been highlighted. The insights presented in this review aim to guide the rational design of next-generation high-entropy materials for sustainable and efficient catalytic processes.

Mesoporous Co-MoS2 with sulfur vacancies: A bifunctional electrocatalyst for enhanced water-splitting reactions in alkaline media

As a graphene-like layered material, molybdenum disulfide (MoS2), has attracted increasing attentions for its promising application in electrocatalysis. Whereas MoS2 still suffers from the sluggish reaction kinetics in oxygen evolution reaction (OER) due to the low density of active sites in most exposed planes. In this work, high density of active sites on MoS2 basal planes has been obtained by synthesizing mesoporous MoS2 with Co doping and sulfur vacancies (VS). The synergy of the mesoporous structure, Co doping, and sulfur vacancies resulted in optimized bifunctional electrocatalytic activity for both hydrogen evolution reaction (HER) and OER in alkaline media. The overpotential required to achieve a current density of 10 mA cm-2 (denoted as η10) is 34 mV for HER and 268 mV for OER, respectively. The two-electrode electrolyzer constructed with the as-prepared cobalt-doped mesoporous MoS2 electrodes exhibited a low bias (η10 = 1.58 V) for overall water splitting. Density functional theory (DFT) calculations confirm the significance of Co doping and the S vacancy defects, which lowers the Gibbs free energy (ΔG) for the formation of the corresponding intermediates.

Synergizing RuO2 with Fe-doped Co2RuO4 for boosting alkaline electrocatalytic oxygen evolution reaction

Designing and development of electrocatalysts with high catalytic capacity and stability for oxygen evolution reaction (OER) is significant for sustainable water splitting. In this study, we rationally designed Fe-doped Co2RuO4/RuO2 heterostructure electrocatalysts on nickel foam (NF) through mixture hydrothermal, ion exchanging, and calcining methods. The synergistic effect between the Fe-Co2RuO4/RuO2 heterogeneous interfaces can result in superior inherent activity. Meanwhile, the unique nanosheet on nanosheet structure delivers abundant exposed active sites, leading to improved catalytic activity. The resultant Fe-Co2RuO4/RuO2 heterostructured catalysts possessed superior OER property, attaining a current density of 50 mA cm-2 with only 253 mV overpotential in 1.0 M KOH alkaline solution, and demonstrating good durability with continuous operation for up to 50 h. This research provides robust support for the research and development of RuO2-based electrocatalysts through effective interface engineering and doping strategies, and opens up new avenues for the industrial application of water splitting technology.

Electrochemical Hydrogen Evolution with Metal-Organic Framework-Derived Catalysts: Strategies for d-Band Modulation by Electronic Structure Modification

The effective use of metal-organic framework (MOF)-based materials in the electrocatalytic hydrogen evolution reaction (HER) relies on the understanding of their structural and electronic properties. While the structure and morphology of MOF-derived catalysts significantly impact HER activity, tuning the d-band structure through electronic structure modulation has emerged as a key factor in optimizing catalytic performance. Techniques such as composition tuning, heteroatom doping, surface modification, and interface engineering were found to be effective methods for manipulating the electronic configuration and, in turn, modulating the d-band. This review systematically explores the design strategies for MOF-derived catalysts by focusing on electronic structure modulation. It provides a detailed discussion of the various methods - used to modulate the electronic structure. Furthermore, the review establishes the relationship between d-band tuning, Gibbs free energy, and electronic structure modulation, supported by both spectroscopic and theoretical evidences.

Highly Conductive Non-Calcined 2D Cu0.3Co0.7 Bimetallic-Organic Framework for Urea Electrolysis in Simulated Seawater

Global clean energy demands can be effectively addressed using the promising approach of hydrogen energy generation combined with less energy consumption. Hydrogen can be generated, and urea-rich wastewater pollution can be mitigated in a low-energy manner using the urea oxidation reaction (UOR). This paper seeks to assemble a unique electrocatalyst of a pristine 2D MOF, [Co(HBTC)(DMF)]n (Co-MUM-3), from 1,3,5-benzenetricarboxylate (BTC) to oxidize urea in simulated seawater. Ni foam (NF)-based working electrodes were fabricated by incorporating a series of heterometallic CuCo-MUM-3 frameworks (Cu0.1Co0.9-MUM-3, Cu0.2Co0.8-MUM-3, Cu0.3Co0.7-MUM-3, and Cu0.4Co0.6-MUM-3), after which their application in the urea oxidation reaction was examined. A very low required overpotential [1.26 V vs reversible hydrogen electrode (RHE) in 1 M KOH + 0.5 M NaCl (simulated seawater) + 0.33 M urea] and a Tafel slope of 112 mV dec-1 could be observed for the Cu0.3Co0.7-MUM-3 electrocatalyst, ensuring the achievement of urea electro-oxidation and hydrogen evolution reactions at a corresponding 10 mA cm-2 electrocatalytic current density. A relatively lower overpotential will be evident compared to other reported pristine MOFs, outperforming the commercial catalyst RuO2 (1.41 V at 10 mA cm-2, 131 mV dec-1) and ensuring considerable stability at significantly high current densities for a minimum of 72 h.

An advanced PdNPs@MoS2 nanocomposite for efficient oxygen evolution reaction in alkaline media

In response to the increasing availability of hydrogen energy and renewable energy sources, molybdenum disulfide (MoS2)-based electrocatalysts are becoming increasingly important for efficient electrochemical water splitting. This study involves the incorporation of palladium nanoparticles (PdNPs) into hydrothermally grown MoS2via a UV light assisted process to afford PdNPs@MoS2 as an alternative electrocatalyst for efficient energy storage and conversion. Various analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS), were used to investigate the morphology, crystal quality, and chemical composition of the samples. Although PdNPs did not alter the MoS2 morphology, oxygen evolution reaction (OER) activity was driven at considerable overpotential. When electrochemical water splitting was performed in 1.0 M KOH aqueous solution with PdNPs@MoS2 (sample-2), an overpotential of 253 mV was observed. Furthermore, OER performance was highly favorable through rapid reaction kinetics and a low Tafel slope of 59 mV dec-1, as well as high durability and stability. In accordance with the electrochemical results, sample-2 showed also a lower charge transfer resistance, which again provided evidence of OER activity. The enhanced OER activity was attributed to a number of factors, including structural, surface chemical compositions, and synergistic effects between MoS2 and PdNPs.

Cold plasma synthesis of phosphorus-doped CoFe2O4 with oxygen vacancies for enhanced OER activity

Spinel-type metal oxides are promising electrocatalysts for the oxygen evolution reaction (OER) due to their unique electronic structure and low cost. Herein, we induced oxygen vacancies and doped phosphorus into CoFe2O4 using cold plasma. The abundant oxygen vacancies enhanced hydrophilicity and modified the electronic structure of CoFe2O4, while the phosphorus doping formed numerous new active centers. The doped P and formed FeP promoted the charge transfer and improved the conductivity of the catalyst. The phosphorus-doped CoFe2O4 exhibited exceptional OER activity with an overpotential of 180 mV at 10 mA cm-2 and a Tafel slope of 65.8 mV dec-1 in an alkaline electrolyte. DFT calculations confirmed that phosphorus doping can improve the charge distribution near the Fermi level and optimize the d-band center position.