Interstitial boron-doped Ni4Mo nanoarray catalyst boosts stable hydrogen evolution reaction

MCM-41 supported NiPCeOx nanoparticles as highly efficient non-noble metal catalyst for hydrolytic dehydrogenation of ammonia borane

Exploring the generation of efficient and long‐lasting bifunctional electrocatalysts obtained from low‐cost transition metal oxides is crucial to the optimal production of hydrogen and oxygen by electrocatalytic water splitting. This study aims to demonstrate the applicability of layered TiO2 nanosheets as support for designing electrocatalysts. We have demonstrated the performance by decorating the TiO2 support with NiCo2O4 nanoparticles (NiCo2O4/TiO2) as catalysts for electrocatalytic overall water splitting. Moreover, the corrosion effect of usually used carbon‐based supporting materials can decrease the working efficiency and, thus, the overall performance of the catalysts. In this aspect, TiO2 can be a better alternative to carbon‐based systems. Layered TiO2 was synthesized at room temperature, and a simple heat treatment protocol was employed for the large‐scale synthesis of NiCo2O4/TiO2. TiO2 facilitated the formation of smaller NiCo2O4 nanoparticles, also improving the dispersion. This bifunctional electrocatalyst exhibits high OER and HER performance with a low overpotential of 309 mV and 185 mV respectively, at a current density of 10 mA cm−2. TiO2 supported catalyst also exhibits other advantages like remarkable durability in the alkaline medium along with high turnover frequency (TOF) values. This inexpensive catalyst can deliver a current density of 10 mA cm−2 at only 1.64 V with a steady performance for more than 12 h for overall water splitting. Thus, this homemade system provides a proficient and low‐cost alternative to the more expensive systems such as RuO2, IrO2 or Pt for the electrochemical water splitting applications.

The development of low-cost and high-efficiency catalysts for the hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) is still a challenging technology. Herein, ultrafine MoOx-doped Ni nanoparticles (~3.0 nm) were anchored on g-C3N4@glucose-derived nitrogen-doped carbon nanosheets via a phosphate-mediated method. The strong adsorption of phosphate-mediated nitrogen-doped carbon nanosheets (PNCS) for metal ions is a key factor for the preparation of ultrasmall Ni nanoparticles (NPs). Notably, the alkaline environment formed by the reduction of metal ions removes the phosphate from the PNCS surface to generate P-free (P)NCS so that the phosphate does not participate in the subsequent catalytic reaction. The synthesized Ni-MoOx/(P)NCS catalysts exhibited outstanding catalytic properties for the hydrolysis of AB, with a high turnover frequency (TOF) value of up to 85.7 min-1, comparable to the most efficient noble-metal-free catalysts and commercial Pt/C catalyst ever reported for catalytic hydrogen production from AB hydrolysis. The superior performance of Ni-MoOx/(P)NCS can be ascribed to its well-dispersed ultrafine metal NPs, abundant surface basic sites, and electron-rich nickel species induced by strong electronic interactions between Ni-MoOx and (P)NCS. The strategy of combining multiple modification measures adopted in this study provides new insights into the development of economical and high-efficiency noble-metal-free catalysts for energy catalysis applications.

In this work, three novel catalysts were prepared by 2.5, 5.0, and 10.0wt.% facile impregnation with an iron and molybdenum mixed oxide (Fe/Mo) on an aluminum pillared clay (Al-PILC) support. These materials were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), temperature programed reduction (TPR), and nitrogen (N2) physisorption at 77K. Characterizations indicated that the metal particles were dispersed on the surface of the three catalysts, and the interlayer d001 spacing of the pillared material remained unchanged after the impregnation process. The catalytic tests showed good results for DBT oxidation using the synthesized catalysts, with high turnover frequency (TOF) values, particularly for the material with 5.0wt.% Fe/Mo. Theoretical calculations were carried out at the density functional theory (DFT) level, to investigate how the DBT molecules were adsorbed onto the surface of the mixed oxide. The lowest energy proposal was obtained when both Fe and Mo were present at the active sites, indicating a possible synergistic effect of the metals on catalyst activity. Reuse tests indicated that the catalysts could be employed effectively for up to 3cycles in a row, then a decrease in activity occurred and the active sites needed to be regenerated.

Facile synthesis of NiPt–CeO2 nanocomposite as an efficient catalyst for hydrogen generation from hydrazine borane

Novel lignin-based single atom catalysts as peroxymonosulfate activator for pollutants degradation: Role of single cobalt and electron transfer pathway

Oxidovanadium(IV) complex of β‐octabromo‐meso‐tetraphenylporphyrin, {[VIVO(TPPBr8)], 2} was synthesized by self‐catalytic oxidative bromination of meso‐tetraphenylporphyrinatooxidovanadium(IV) {[VIVO(TPP), 1} in excellent yield under mild conditions at 25 °C and its structure was confirmed by single crystal X‐ray study. UV‐Vis and 1H NMR spectra further confirmed that the meso‐phenyl rings are not brominated and thus emphasizes on the selectivity as well as synthetic importance of this catalytic method. In the presence of substrates e. g. phenol derivatives, 1 biomimics the vanadium bromoperoxidase (VBPO) enzyme and catalyses the oxidative bromination of substrates in water at 25 °C. Remarkably, 2 also catalyses the oxidative bromination of phenol derivatives under similar reaction conditions with very high turnover frequency (TOF) values (ca. 29 s−1) along with its recyclability. It was found that 2 showed superior catalytic performance as compared to 1 because of its electron deficient nature due to electron withdrawing bromo substituents and robust saddle shaped nonplanar structure (further supported by DFT studies).

ZnCl 2/phosphonium halide: An efficient Lewis acid/base catalyst for the synthesis of cyclic carbonate

Nitrous oxide (N2O) is a potent greenhouse gas and an ozone‐depleting substance. Electrocatalytic N2O reduction (e‐N2ORR) is a promising approach to remove N2O from the air under ambient conditions. However, developing noble‐metal‐free e‐N2ORR electrocatalysts with high Faradaic efficiency (FE) and turnover frequency (TOF) remains a challenge because of the weak binding of N2O and the high kinetic barrier for deoxygenation reaction. In this work, inspired by the multinuclear copper active site of nitrous oxide reductases, a binuclear copper complex of 3,5‐diamino‐1,2,4‐triazole supported on carbon black of Ketjenblack (CuHdatrz/KB) was utilized for the e‐N2ORR at pH 13 and 298 K. CuHdatrz/KB achieves a high FE of ≈100% at ‐0.3 V vs. RHE for the e‐N2ORR to N2 and TOF up to ≈700 h‐1, which is one–two orders of magnitude higher than those of the previously reported molecular‐based catalysts. In situ X‐ray absorption spectroscopy confirmed that Cu(II) ions of CuHdatrz/KB are reduced to Cu(I) keeping the binuclear core, suggesting that the multinuclear copper active sites is crucial to efficiently catalyze the e‐N2ORR like the nitrous oxide reductase.

Hydrogen is an alternative fuel that can play a critical role in achieving net zero emissions, leading to global environment sustainability. An iridium-immobilized catalyst based on polyethyleneimine (PEI) was synthesized and utilized for hydrogen production via formic acid dehydrogenation (FADH). Iridium complex is cross-linked with its ligand and PEI to form the immobilized catalyst, where the iridium content could be easily varied in the range of 1-10 %. The structure of the iridium-immobilized catalyst was confirmed using solid-state NMR, DNP NMR, and FTIR spectroscopies. The iridium-immobilized catalyst with PEI showed excellent catalytic activity for FADH, exhibiting the catalyst's highest turnover frequency (TOF) value of 73 200 h-1 and a large turnover number (TON) value of over 1 130 000. The catalyst could be used for continuous hydrogen production via FADH, exhibiting high durability for over 2 000 h with TON value of 332 889 without any degradation in catalytic activity. The obtained hydrogen gas was evaluated for power generation using a standard fuel cell, as well as achieved 5 h of stable power generation.

A rational designing nanostructured Earth-abundant and non-precious electrocatalysts for promoting an anodic oxygen evolution reaction (OER) is crucial for cutting-edge energy conversion and storage fields. Herein, we demonstrate a porous structured three-dimensional (3-D) FeP nanosheets on NiO modified Ni electrode (PS-3D-FeP@NiO|Ni) using of a facile and two-step electrodeposition strategy that exhibits enhanced OER under alkaline electrolyte. The as-developed porous-structured 3-D FeP nanosheets on NiO modified Ni electrode exhibits the best OER catalytic activity in relations of low onset potential (ղonset) of ~1.37 V (vs. RHE), small overpotential (η) of ~0.17 V to produce the current densities of 10 mA cm−2, lower Tafel slope value of ~40.0 mV/dec, higher turn-over frequency (TOF) of 0.435 s−1, and long-term stability when compared to other CoP@NiOǀNi, NiP@NiOǀNi, CuP@NiOǀNi, NiP|NF (nickel foam), and commercial IrO2|Ni electrodes established in this study. The anodic current density is calculated at the potential of ~1.80 V to be ~580, ~365, ~145, ~185, ~516, and 310 mA cm−2 for PS-3D-FeP@NiO|Ni, CoP@NiOǀNi, NiP@NiOǀNi, CuP@NiOǀNi, IrO2|Ni, and FeP|NF electrodes, respectively. The porous structured 3-D FeP nanosheets on NiO modified Ni electrode demonstrated a highest current density of ~580 mA cm−2 at ~1.80 V in comparison to other electrodes employed in the current investigation. The outperforming OER activity of PS-3D-FeP@NiO|Ni is majorly associated to its porous-structured 3-D sheet-like morphology, large amount of electrochemical active surface area, high electrical conductance characteristics and self-activated/supported active sites, facilitating the catalytic properties. The surface morphology, crystalline structure, chemical composition, and distribution of Fe, P and O elements have not been altered significantly after had a long-term OER test. These experimental results reveal that further optimization of porous structured 3D FeP nanomaterials is highly anticipated for practical water electrolysis systems.

A set of supported Co3O4 catalysts have been designed and prepared to study the effect of textural characteristics and Brønsted acid sites concentration of MWW zeolite support, as well as cobalt loading on catalyst activity. Detailed characterization of the catalysts with a thorough study on their performance in the total oxidation of toluene and propane revealed that MCM-22 is the optimal support and that increasing Si/Al and decreasing external surface of MCM-22 positively affect the activity of supported Co3O4 catalysts, which is determined by their low-temperature reducibility. The activity of the Co/MCM-22 catalysts increased with cobalt content (5-20 wt %), consistent with enhancing the amount of low-temperature reducible Co3O4. The optimized catalyst containing 20% Co supported on dealuminated MCM-22 presented high turnover frequency (TOF) values in both toluene (2.6 × 10-5 s-1 at 270 °C) and propane (3.9 × 10-5 s-1 at 215 °C) oxidation and was characterized by outstanding cycling stability, long-term durability, water tolerance, and sintering resistance.

The recyclable metal nanoparticle catalysts, rhodium in aluminum oxyhydroxide [Rh/AlO(OH)] and iridium in aluminum oxyhydroxide [Ir/AlO(OH)], were simply prepared from readily available reagents. The catalysts showed high activities in the hydrogenation of various arenes and ketones under mild conditions. Selective hydrogenation was possible for bicyclic and tricyclic arenes in high yields. The catalysts were active at room temperature even with a hydrogen balloon. Also, the catalysts showed high turnover frequency (TOF) values under solventless conditions at 75 °C under 4 atm hydrogen pressure: ca. 1700 h−1 in the hydrogenation of benzene. Furthermore, Rh/AlO(OH) can be reused for at least 10 times without activity loss. The catalysts were characterized by the transmission electron microscopy (TEM), powder X‐ray diffraction (XRD), inductively coupled plasma (ICP), energy dispersive X‐ray analysis (EDX), X‐ray photoelectron spectroscopy (XPS), nitrogen adsorption and hydrogen chemisorption experiments. The sizes of rhodium and iridium particles were estimated to be 3–4 nm and 2–3 nm, respectively. Aluminum oxyhydroxide nanofibers of these catalysts have surface areas of 500–600 m2 g−1.

The development of strategies for tuning the electronic structure of the metal sites in single-atom catalysts (SACs) is the key to optimizing their activity. Herein, we report that iodine doping within the carbon matrix of a cobalt-nitrogen-carbon (Co-N-C) catalyst can effectively modulate its electronic structure and catalytic activity toward the hydrogen evolution reaction (HER). The iodine-doped Co-N-C catalyst shows exceptional HER activity in acid with an overpotential of merely 52 mV at 10 mA cm-2, a small Tafel slope of 56.1 mV dec-1, making it among the best SACs based on both precious and nonprecious metals. Moreover, this catalyst possesses a high turnover frequency (TOF) value of 1.88 s-1 (η = 100 mV), which is about 1 order of magnitude larger than that (0.2 s-1) of the iodine-free counterpart. Experimental and theoretical studies demonstrate that the introduction of iodine dopants lowers the chemical oxidation state of the Co sites, resulting in the optimized hydrogen adsorption and facilitated HER kinetics. This work provides an alternative strategy to regulate the electronic structure of SACs for improved performance.

A catalytic system was developed to enable the use of industrially available terpenes (e.g., β‐myrcene, β‐farnesene) in hydroaminomethylation to obtain renewable building blocks for surfactants in two steps. This homogeneously catalyzed tandem reaction includes both hydroformylation and enamine condensation steps, followed by hydrogenation. Under the optimized conditions, the Rh/1,2‐bis(diphenylphosphino)ethane catalytic system delivers products in high yields (70 %) after short reaction times (3 h) with unprecedentedly high turnover frequency (TOF) values for the hydroformylation of 1,3‐dienes of over 739 mol mol−1 h−1. This is the highest TOF reported to date for the hydroformylation of a 1,3‐diene. Furthermore, regioselectivities of 97 % and above were observed in the hydroformylation step, which is extraordinarily high for the conversion of 1,3‐dienes. The terpene‐derived amines obtained were further functionalized to quaternary ammonium compounds that were found to show surface activity quite similar to that of industrially available quaternary ammonium compounds. The hydroaminomethylation of terpenes achieves higher step efficiency than industrial means and makes use of an alternative, renewable feedstock to synthesize more environmentally friendly surfactants.