Unstable Ni leaching in MOF-derived PtNi-C catalyst with improved performance for alcohols fuel electro-oxidation

Surface-modified composites of metal-organic framework and wood-derived carbon for high-performance supercapacitors

The renewable nature, high carbon content, and unique hierarchical structure of wood-derived carbon make it an optimal self-supporting electrode for energy storage. However, the limitations in specific surface area and electrical conductivity defects pose challenges to achieving satisfactory charge storage in wood-derived carbon electrodes. Therefore, exploring diverse and effective surface strategies is crucial for enhancing the electrochemical energy storage performance. Herein, a decoration technique for enhancing aesthetic appeal involves applying a metal-organic framework (Ni/Co-MOF) containing nickel and cobalt onto the inner walls of wood tracheids. The sequential modification steps include carbonization, oxidation activation, and acid-etching. The Ni/NiO/CoO-CW-4 electrode, made by acid-etching carbonized wood (CW) doped with nickel, nickel oxide, and cobalt oxide for 4 h, has excellent surface area and pore size distribution, high graphitization degree, and exceptional conductivity. Furthermore, surface modification optimizes the surface chemistry and phase composition, resulting in a 0.8 mm thick Ni/NiO/CoO-CW-4 electrode with an exceptionally high areal capacitance of 16.76 F cm-2 at 5 mA cm-2. Meanwhile, the fabricated solid-state supercapacitor achieves an impressive energy density of 0.67 mWh cm-2 (8.38 mWh cm-3) at 2.5 mW cm-2 (31.25 mW cm-3), surpassing representative modified wood-based carbon electrodes by approximately 2-7 times. Additionally, the supercapacitor demonstrates exceptional stability, maintaining 96.21 % of capacitance even over 10,000 cycles. The parameters presented here demonstrate a significant improvement compared to those typically observed in most modified wood-derived carbon-based supercapacitors, effectively addressing common issues of low energy density and suboptimal cycling performance with wood carbon composites.

Unveiling the scope and perspectives of MOF-derived materials for cutting-edge applications

Although synthesis and design of MOFs are crucial factors to the successful implementation of targeted applications, there is still lack of knowledge among researchers about the synthesis of MOFs and their derived composites for practical applications. For example, many researchers manipulate study results, and it has become quite difficult to quit this habit specifically among the young researchers Undoubtedly, MOFs have become an excellent class of compounds but there are many challenges associated with their improvement to attain diverse applications. It has been noted that MOF-derived materials have gained considerable interest owing to their unique chemical properties. These compounds have exhibited excellent potential in various sectors such as energy, catalysis, sensing and environmental applications. It is worth mentioning that most of the researchers rely on commercially available MOFs for use as precursor supports, but it is an unethical and wrong practice because it prevents the exploration of the hidden diversity of similar materials. The reported studies have significant gaps and flaws, they do not have enough details about the exact parameters used for the synthesis of MOFs and their derived materials. For example, many young researchers claim that MOF-based materials cannot be synthesized as per the reported instructions for large-scale implementation. In this regard, current article provides a comprehensive review of the most recent advancements in the design of MOF-derived materials. The methodologies and applications have been evaluated together with their advantages and drawbacks. Additionally, this review suggests important precautions and solutions to overcome the drawbacks associated with their preparation. Applications of MOF-derived materials in the fields of energy, catalysis, sensing and environment have been discussed. No doubt, these materials have become excellent class but there are still many challenges ahead to specify it for the targeted applications.

Mo-Ni-based Heterojunction with Fine-customized d-Band Centers for Hydrogen Production Coupled with Benzylamine Electrooxidation in Low Alkaline Medium

Benzylamine electrooxidation reaction (BAOR) is a promising route to produce value-added, easy-separated benzonitrile, and effectively hoist H2 production. However, achieving excellent performance in low alkaline medium is a huge challenge. The performance is intimately correlated with effective coupling of HER and BAOR, which can be achieved by manipulating the d-electron structure of catalyst to regulate the active species from water. Herein, we constructed a biphasic Mo0.8 Ni0.2 N-Ni3 N heterojunction for enhanced bifunctional performance toward HER coupled with BAOR by customizing the d-band centers. Experimental and theoretical calculations indicate that charge transfer in the heterojunction causes the upshift of the d-band centers, which one side facilitates to decrease water activation energy and optimize H* adsorption on Mo0.8 Ni0.2 N for promoting HER activity, the other side favors to more easily produce and adsorb OH* from water for forming NiOOH on Ni3 N and optimizing adsorption energy of benzylamine, thus catalyzing BAOR effectively. Accordingly, it shows an industrial current density of 220 mA cm-2 at 1.59 V and high Faradaic efficiencies (>99 %) for H2 production and converting benzylamine to benzonitrile in 0.1 M KOH/0.5 M Na2 SO4 . This work guides the design of excellent bifunctional electrocatalysts for the scalable production of green hydrogen and value-added products.

Enhanced photo-Fenton activity and stability for sulfamethoxazole degradation by FeS2@TiO2 heterojunction derived from MIL-125

FT-x composites with core-shell structure (FT = FeS₂@TiO₂, x represents the mass ratio of the used FeCl₃·6H₂O to MIL-125) were fabricated by a hydrothermal method using MIL-125(Ti) as a self-sacrificing template. Both the photo-Fenton activity and stability of the FT-1 were improved greatly in comparison with its counterparts due to the unique core-shell structure and synergistic effect between FeS₂ and TiO₂. Especially, the Fe leaching concentration of FT-1 was approximately 1/10 of the individual FeS₂, benefiting from the protection effect of TiO₂ shell. Under dark condition, the formed FeOOH occupied active sites and inhibited iron cycle as well as H₂O₂ decomposition, leading to the inactivation of FT-1. UV light irradiation not only boosted the catalytic activity but also prevented the FT-1 from reactivity decline owning to the regeneration of Fe²⁺ by photogenerated electrons and continuous generation of ·OH. Experimental and DFT calculation results indicated that a type-II heterojunction was formed, in which photogenerated electrons were transferred from FeS₂ core to TiO₂ shell, accelerating charge separation and further boosting sulfamethoxazole (SMX) degradation. FT-1 displayed outstanding photo-Fenton activity in wide pH ranged from 2 to 6 and good anti-interfering ability toward impurities in water matrix. Besides, the reusability of FT-1 was good, in which 90% SMX degradation was maintained even after 5 runs. Noteworthy, the photo-Fenton activity was recovered via a revulcanization process, in which FeOOH was completely transformed into FeS₂. This founding provided insights for the design and construction of heterojunction with both excellent photo-Fenton activity and stability.

ZIF-67-derived CoP/NC effectively supported Pt nanoparticles for methanol oxidation reaction

Metal-support interaction plays an important role in the catalysis reaction, and an effective support is highly desired in the hybrid catalyst construction. Herein, we demonstrated an effective catalyst system by coupling Pt nanoparticles over the ZIF-67-derived CoP/NC support for methanol oxidation reaction (MOR) in acidic and alkaline solutions. The results indicated that the Pt-CoP/NC catalyst showed high catalytic activity and stability for MOR owing to the oxophilic properties of CoP and the strong metal-support interaction, as well supported by the electrochemical measurements and the spectroscopic analysis, which far exceeded that of the Pt-Co/NC and commercial Pt/C catalysts. Specifically, the forward peak current density of the Pt-CoP/NC catalyst was 74.2 mA cm^-2 for MOR in an acidic electrolyte, which was 2.2 times higher than that of a commercial Pt/C catalyst. Further, in an alkaline electrolyte, the Pt-CoP/NC catalyst showed the highest forward peak current density of 118.6 mA cm^-2, which was 4.5 times higher than that of a commercial Pt/C catalyst. High catalytic kinetics and stability for MOR were also carefully discussed. Moreover, the Pt-CoP/NC catalyst exhibited excellent anti-poisoning ability in comparison to the Pt-Co/NC and commercial Pt/C catalysts with the help of the CO-stripping technique. The current work would be instructive for high-performance catalyst system construction based on the ZIF-67-derived CoP/NC support.

Pt/Mn3O4 cubes with high anti-poisoning ability for C1 and C2 alcohol fuel oxidation

Pt particles anchored onto Mn₃O₄ cubes were found to have high anti-CO poisoning abilities for C1- and C2-alcohol fuel oxidations in acid electrolyte, due to an electronic effect that enriched the surfaces of the Pt particles with electrons and due to the oxophilicity of Mn₃O₄ in the system.

Efficient synergism of V2O5 and Pd for alkaline methanol electrooxidation

Efficient synergism of high valence state V and Pd nanoparticles imparted their high catalytic performance and anti-poisoning ability for alkaline methanol electrooxidation.

Liquid-Phase Catalytic Exchange of Hydrogen Isotopes over Platinum on Dual-Modified Graphene

Although liquid-phase catalytic exchange is an environmentally friendly treatment of hydrogen isotopes in recycled water of a nuclear power station, the successive development of hydrophobic catalysts is still needed to meet much higher catalytic exchange efficiency and stability. Herein, a dual-modified graphene with Pt loading was designed by amination and silanization to anchor Pt nanoparticles uniformly, as well as obtain higher hydrophobicity. After coating the reactor walls with poly(dimethylsiloxane), the catalytic exchange efficiency of the dual-modified graphene with lower Pt loadings (Pt/200-S-NH₂-GR) improved up to 91% at 80 °C, which was higher than 80% of only animated graphene (Pt/NH₂-GR) at the same condition. Furthermore, the Pt/200-S-NH₂-GR maintained high stability for at least 10 h in the temperature range of 40-80 °C, while the Pt/NH₂-GR decreased 17% of catalytic exchange efficiency at 80 °C within 10 h. Using the dual-modified strategy for graphene support, high efficiency and stability was achieved for heavy water dedeuteration.

Core@shell PtAuAg@PtAg Hollow Nanodendrites as Effective Electrocatalysts for Methanol and Ethylene Glycol Oxidation

Pt-based catalysts with core@shell structures are widely used in alcohol oxidations due to their excellent catalytic performance. In this work, we synthesized a series of core@shell PtAuAg@PtAg hollow nanodendrites (HNDs) with different compositions by a simple seed-mediated method. The PtAuAg@PtAg HNDs with a hollow core and dendritic shell exhibit excellent catalytic performance for ethylene glycol oxidation reaction (EGOR) and methanol oxidation reaction (MOR). Among these, Pt₃₈Au₂₉Ag₃₃ HNDs have the highest mass activity (12364.0 mA mg_Pt^-1/3278.0 mA mg_Pt^-1) for EGOR and MOR, which is 4.2 times and 5.3 times higher than that of commercial Pt/C (2941.0 mA mg_Pt^-1/617.6 mA mg_Pt^-1), respectively. More importantly, after successive cyclic voltammetry tests, the retained mass activities of Pt₃₈Au₂₉Ag₃₃ HNDs are 3913.8 mA mg_Pt^-1 and 348.3 mA mg_Pt^-1, which are much higher than that of commercial Pt/C as well. The excellent catalytic performance of PtAuAg@PtAg HNDs can be attributed to the structure of HNDs, which can greatly increase the surface area and active sites, as well as the electronic and synergistic effects among Pt, Au, and Ag. This research may provide new ideas for the development of high-efficiency hollow catalytic materials for EGOR and MOR.

One-pot synthesis of rugged PdRu nanosheets as the efficient catalysts for polyalcohol electrooxidation

Recently, intensive attention has been attracted to the two-dimensional metal nanosheets, owing to their excellent electrocatalytic performance for direct alcohol fuel cells (DAFCs). Herein, PdRu nanosheets have been synthesized successfully by a facile one-pot method. The rugged nanosheet structure provided plentiful surface active sites to enhance the electrocatalytic activity. Moreover, benefiting from the synergistic effect and improved electronic structure, PdRu NSs exhibited splendid electrocatalytic performance in ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR). Specifically, the mass activity of PdRu NSs was 1.72 and 3.69 times over those of Pd NSs and Pd/C catalysts in EGOR. Moreover, PdRu NSs displayed the largest mass activity in GOR, 1.48 and 2.47 times as large as Pd NSs and Pd/C catalysts. The results of stability tests demonstrated that the durability of PdRu NSs was the highest among the obtained catalysts. This work plays a directive role on the in-depth engineering on Pd-based catalysts with nanosheet architectures.

Hollow Pd/Te nanorods for the effective electrooxidation of methanol

Methanol electrooxidation is significant in realizing effective C1 liquid fuel applications. Herein, hollow Pd/Te nanorods were fabricated and evaluated for methanol oxidation, and they were found to exhibit high catalytic efficiency for methanol oxidation in alkaline electrolyte compared to Pd or Pd/C catalysts. The hybrid structure of hexagonal crystal Te and face-centered cubic Pd was formed by microwave assisted Pd nanoparticle deposition over the surface of Te nanorods. Strong electronic effects and facile oxophilic properties were indicated in the Pd/Te system by spectroscopic analysis, which mainly accounts for the high catalytic performance for methanol oxidation. Specifically, they showed a peak current density of 90.1 mA cm^-2 for methanol oxidation, around 3.5 times higher than that of commercial Pd/C (26.3 mA cm^-2). High catalytic stability was also observed for Pd/Te, with a current retention of 64.3% after 3600 s of chronoamperometric testing, much higher than for Pd catalysts (20.1%). High anti-CO poisoning ability of the Pd/Te catalyst was demonstrated in the CO-stripping voltammetry results, and faster catalytic kinetics were also observed for this catalyst system. The electron-rich state of Pd and high active site exposure are responsible for the high performance of the Pd/Te catalyst in methanol oxidation.

Efficient alcohol fuel oxidation catalyzed by a novel Pt/Se catalyst

Selenium spheres decorated with Pt nanoparticles were found to be efficient for alcohol fuel oxidation in fuel cells.