Regulating the electronic structure of Fe-based metal organic frameworks by electrodeposition of Au nanoparticles for electrochemical overall water splitting

Recent Progress of Modulating Pristine Metal-Organic Frameworks for Oxygen Reaction Revolution

Highly efficient and stable oxygen evolution reaction (OER) electrocatalysts are essential for electrochemical water splitting. Among non-noble metal-based catalysts, metal-organic frameworks (MOFs) have recently emerged as particularly promising candidates due to their exceptional surface areas, hierarchical porous structures, and tunable morphologies and compositions. The rational regulation of the morphology and electronic structure of pristine MOFs is considered a critical pathway for enhancing active sites and structural stability, thereby significantly boosting the OER catalytic performance. This review systematically presents the recent advancements in modulating pristine MOFs via heterogeneous metal doping, ligand substitution, and hybrid composite construction. With particular emphasis on synthetic methods, modification mechanisms, and the OER properties of MOFs, we analyze the fundamental relationships between structural modifications and electrocatalytic performance. Through the systematic analysis of existing research achievements, this review provides a holistic assessment of current state-of-the-art developments, identifies critical challenges, and proposes future research directions with practical implications for OER electrocatalyst design.

Construction of 2D CoFe-MOF derived from LDH electrocatalyst for efficient oxygen and urea evolution

Two-dimensional metal-organic framework (2D MOF) materials have significant development prospects in the technology of urea-assisted water electrolysis for hydrogen production. However, the poor conductivity, low mass permeability, and stability have limited their development in electrocatalysis. Here, CoFe-BDC is synthesized using layered double hydroxides (LDH) as the template. The effect of different ligands of CoFe-MOF on the microstructure and electrocatalytic performance is systematically investigated. Terephthalic acid has the weakest destructive ability and strongest coordination ability due to its high symmetry in spatial structure and its weakest acidity than other ligands, leading to the production of massive active sites. CoFe-BDC has the best electrocatalytic activity (oxygen evolution reaction (OER): η100 = 258 mV, urea oxidation reaction (UOR): η100 = 1.34 V, overall water splitting (OWS): E100 = 1.76 V). CoFe-BDC is observed to undergo a catalytic transformation to FeOOH at a reconstruction voltage of 1.4 V via in situ Fourier transform infrared spectroscopy and Raman spectroscopy. This study provides a new approach of 2D MOFs materials using template method for water electrolysis.

Hybridization of metal-organic frameworks and MXenes: Expanding horizons in supercapacitor applications

Metal-organic frameworks (MOFs) and MXenes have gained prominence in the queue of advanced material research. Both materials' outstanding physical and chemical characteristics prominently promote their utilization in diverse fields, especially the electrochemical energy storage (EES) domain. The collective contribution of extremely high specific surface area (SSA), customizable pores, and abundant active sites propose MOFs as integral materials for EES devices. However, conventional MOFs endure low conductivity, constraining their utility in practical applications. The development of hybrid materials via integrating MOFs with various conductive materials stands out as an effective approach to improvising MOF's conductivity. MXenes, formulated as two-dimensional (2D) carbides and nitrides of transition metals, fall in the category of the latest 2D materials. MXenes possess extensive structural diversity, impressive conductivity, and rich surface chemical characteristics. The electrochemical characteristics of MOF@MXene hybrids outperform MOFs and MXenes individually, credited to the synergistic effect of both components. Additionally, the MOF derivatives coupled with MXene, exhibiting unique morphologies, demonstrate outstanding electrochemical performance. The important attributes of MOF@MXene hybrids, including the various synthesis protocols, have been summarized in this review. This review delves into the architectural analysis of both MOFs and MXenes, along with their advanced hybrids. Furthermore, the comprehensive survey of the latest advancements in MOF@MXene hybrids as electroactive material for supercapacitors (SCs) is the prime objective of this review. The review concludes with an elaborate discussion of the current challenges faced and the future outlooks for optimizing MOF@MXene composites.

A bimetallic NiFe MOF with ultra-thin two-dimensional nanosheet structure effectively accelerates oxygen evolution reaction

To address the shortage of fossil energy, the development of affordable and efficient non-precious metal catalysts for oxygen evolution reaction (OER) from electrocatalytic water splitting is still a crucial challenge. Herein, the bimetallic NiFe metal-organic frameworks (MOFs) are synthesized by hydrothermal and electro-deposition. Benefiting from the synergistic effect of Fe and Ni, the catalyst demonstrates extraordinary activity, which exhibits favorable OER catalytic activity in 1 M KOH solution with an overpotential of 206 mV at 10 mA cm-2. Meanwhile, the obtained NiFe-NDC presents promising stability in the 20 h test at 50 mA cm-2.

Facile synthesis of CeO2-decorated W@Co-MOF heterostructures as a highly active and durable electrocatalyst for overall water splitting

Rational coupling of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts is extremely important for practical overall water splitting; however, it is still challenging to construct such bifunctional heterostructures. Herein, a CeO2/W@Co-MOF/NF bifunctional electrocatalyst was prepared via a two-step in situ growth method involving an electrodeposition process. The incorporation of the W element enhanced the electronic interaction and enlarged the electrochemical surface area. After the electrodeposition of CeO2, the obtained CeO2/W@Co-MOF/NF possessed abundant heterointerfaces with a modulated local distribution, which promoted water dissociation and rapid electrocatalytic kinetics. In particular, it required very low overpotentials of 239 mV and 87 mV to reach a current density of 10 mA cm-2 in OER and HER, respectively. A corresponding alkaline electrolysis cell afforded a cell voltage of 1.54 V at 10 mA cm-2 to boost overall water splitting. This work provides a feasible strategy to fabricate MOF-based complexes and explores their possible use as bifunctional catalysts toward overall water splitting.

Iron Active Center Coordination Reconstruction in Iron Carbide Modified on Porous Carbon for Superior Overall Water Splitting

In this work, a novel liquid nitrogen quenching strategy is engineered to fulfill iron active center coordination reconstruction within iron carbide (Fe3C) modified on biomass-derived nitrogen-doped porous carbon (NC) for initiating rapid hydrogen and oxygen evolution, where the chrysanthemum tea (elm seeds, corn leaves, and shaddock peel, etc.) is treated as biomass carbon source within Fe3C and NC. Moreover, the original thermodynamic stability is changed through the corresponding force generated by liquid nitrogen quenching and the phase transformation is induced with rich carbon vacancies with the increasing instantaneous temperature drop amplitude. Noteworthy, the optimizing intermediate absorption/desorption is achieved by new phases, Fe coordination, and carbon vacancies. The Fe3C/NC-550 (550 refers to quenching temperature) demonstrates outstanding overpotential for hydrogen evolution reaction (26.3 mV at -10 mA cm-2) and oxygen evolution reaction (281.4 mV at 10 mA cm-2), favorable overall water splitting activity (1.57 V at 10 mA cm-2). Density functional theory (DFT) calculations further confirm that liquid nitrogen quenching treatment can enhance the intrinsic electrocatalytic activity efficiently by optimizing the adsorption free energy of reaction intermediates. Overall, the above results authenticate that liquid nitrogen quenching strategy open up new possibilities for obtaining highly active electrocatalysts for the new generation of green energy conversion systems.

Transforming electrochemical hydrogen Production: Tannic Acid-Boosted CoNi alloy integration with Multi-Walled carbon nanotubes for advanced bifunctional catalysis

The dimensions of alloy nanoparticles or nanosheets have emerged as a critical determinant for their prowess as outstanding electrocatalysts in water decomposition. Remarkably, the reduction in nanoparticle size results in an expanded active specific surface area, elevating reaction kinetics and showcasing groundbreaking potential. In a significant leap towards innovation, we introduced tannic acid (TA) to modify multi-walled carbon nanotubes (MWCNTs) and CoNi alloys. This ingenious strategy not only finely tuned the size of CoNi alloys but also securely anchored them to the MWCNTs substrate. The resulting synergistic "carbon transportation network" accelerated electron transfer during the reaction, markedly enhancing efficiency. Furthermore, the exceptional synergy of Co and Ni elements establishes Co0.84Ni1.69/MWCNTs as highly efficient electrocatalysts. Experimental findings unequivocally demonstrate that TA-Co0.84Ni1.69/MWCNTs require minimal overpotentials of 171 and 294 mV to achieve a current density of ± 10 mA cm-2. Serving as both anode and cathode for overall water splitting, TA-Co0.84Ni1.69/MWCNTs demand a low voltage of 1.66 V at 10 mA cm-2, maintaining structural integrity throughout extensive cyclic stability testing. These results propel TA-Co0.84Ni1.69/MWCNTs as promising candidates for future electrocatalytic advancements.

Structural Engineering of Co-Metal-Organic Frameworks via Ce Incorporation for Improved Oxygen Evolution

The rational design of metal-organic framework (MOF)-based electrocatalysts plays a key role in achieving high-efficiency oxygen evolution reaction (OER). Herein, a synergetic morphology and electronic structure engineering strategy are proposed to design a Co-MOF nanoflower grown on carbon paper via rare-earth cerium doping (CoCe-MOF/CP). Compared with Co-MOF/CP, the developed CoCe-MOF/CP exhibited superior OER performance with a low overpotential of 267 mV at 10 mA cm-2 and outstanding long-term stability over 100 h. Theoretical calculations show that the unique 4f valence electron structure of Ce induced charge redistribution of the Co-MOF surface through the strong Co 3d-O 2p-Ce 4f orbital electronic coupling below the Fermi level. Ce-doped plays a key role in the engineering of the electronic states of the Co sites to endow them with the optimal free energy landscape for enhanced OER catalytic activity. This work provides new insights into comprehending the RE-enhanced mechanism of electrocatalysis and provides an effective strategy for the design of MOF-based electrocatalysts.

Nanoscale designing of metal organic framework moieties as efficient tools for environmental decontamination

Environmental pollutants, being a major and detrimental component of the ecological imbalance, need to be controlled. Serious health issues can get intensified due to contaminants present in the air, water, and soil. Accurate and rapid monitoring of environmental pollutants is imperative for the detoxification of the environment and hence living beings. Metal-organic frameworks (MOFs) are a class of porous and highly diverse adsorbent materials with tunable surface area and diverse functionality. Similarly, the conversion of MOFs into nanoscale regime leads to the formation of nanometal-organic frameworks (NMOFs) with increased selectivity, sensitivity, detection ability, and portability. The present review majorly focuses on a variety of synthetic methods including the ex situ and in situ synthesis of MOF nanocomposites and direct synthesis of NMOFs. Furthermore, a variety of applications such as nanoabsorbent, nanocatalysts, and nanosensors for different dyes, antibiotics, toxic ions, gases, pesticides, etc., are described along with illustrations. An initiative is depicted hereby using nanostructures of MOFs to decontaminate hazardous environmental toxicants.

MOFs for Electrochemical Energy Conversion and Storage

Metal organic frameworks (MOFs) are a family of crystalline porous materials which attracts much attention for their possible application in energy electrochemical conversion and storage devices due to their ordered structures characterized by large surface areas and the presence in selected cases of a redox-active porous skeleton. Their synthetic versatility and relevant host-guest chemistry make them suitable platform for use in stable and flexible conductive materials. In this review we summarize the most recent results obtained in this field, by analyzing the use of MOFs in fuel and solar cells with special emphasis on PEMFCs and PSCs, their application in supercapacitors and the employment in batteries by differentiating Li-, Na- and other metal ion-batteries. Finally, an overview of the water splitting reaction MOF-catalyzed is also reported.

Hydrogen Production Technology Promotes the Analysis and Prospect of the Hydrogen Fuel Cell Vehicles Development under the Background of Carbon Peak and Carbon Neutrality in China

Hydrogen fuel cell vehicles have always been regarded as the main direction for developing new energy vehicles in the future due to their advantages of zero emission, high cruising range, and strong environmental adaptability. Currently, although the related technologies have gradually matured, there are still many factors hindering its development. One of the main reasons is that the price of hydrogen fuel increases the cost of using vehicles, which puts it at a competitive disadvantage compared with traditional fuel vehicles and pure electric vehicles. Herein, we summarize the recent development status of hydrogen fuel cell vehicles at home and abroad, and analyze the cost and sustainability brought by the latest scientific research progress to the hydrogen production industry, which is derived from basic research on electrocatalysts used in industrial electrocatalytic water splitting with an alkaline electrolyte. Finally, the development of hydrogen fuel cell vehicles was analyzed and prospected, which is one of the main application fields of hydrogen in the future.