Development Of Catalysts Research Articles

Bimetallic Ni and Pt single atoms anchored on nitrogen–phosphorus doped porous carbon fibers to achieve significant electrocatalytic hydrogen evolution

The commercial application of water electrolysis for hydrogen production requires the development of low precious metal catalysts with a high crustal abundance. One feasible strategy is to utilize bimetallic catalysts composed of both transition and precious metals. In this study, a novel N/P-doped Ni/Pt bimetallic catalyst is developed (NiPt@C-NP, 3.68 % Ni, 0.2 % Pt) using polyacrylonitrile fibers as an inexpensive carbon source for catalyst support. Due to strong anchoring from the N and P heteroatoms, the nickel and platinum species are mono-atomically dispersed throughout the catalyst. Under acidic conditions, NiPt@C-NP exhibits a hydrogen evolution overpotential of 89 mV (10 mA cm−2), whereas an unsupported platinum catalyst gives an overpotential of 302 mV. The mass activity of Pt in NiPt@C-NP reaches 36.17 A mgPt−1, which is 33 times higher than 20 % Pt/C (1.07 A mgPt−1). Density functional theory (DFT) calculations reveal that synergistic interactions between Ni and Pt significantly increase the density of state near the Fermi level of NiPt@C-NP, resulting in a reduced bandgap and an enhanced charge transfer capability. Furthermore, the Gibbs free energy at the Pt and Ni sites is − 0.25 and − 0.63 eV, respectively, indicating fast reaction kinetics.

Creating Atomically Iridium-Doped PdOx Nanoparticles for Efficient and Durable Methane Abatement.

The urgent environmental concern of methane abatement, attributed to its high global warming potential, necessitates the development of methane oxidation catalysts (MOC) with enhanced low-temperature activity and durability. Herein, an iridium-doped PdOx nanoparticle supported on silicalite-1 zeolite (PdIr/S-1) catalyst was synthesized and applied for methane catalytic combustion. Comprehensive characterizations confirmed the atomically dispersed nature of iridium on the surface of PdOx nanoparticles, creating an Ir4f-O-Pdcus microstructure. The atomically doped Ir transferred more electrons to adjacent oxygen atoms, modifying the electronic structure of PdOx and thus enhancing the redox ability of the PdIr/S-1 catalysts. This electronic modulation facilitated methane adsorption on the Pd site of Ir4f-O-Pdcus, reducing the energy barrier for C-H bond cleavage and thereby increasing the reaction rate for methane oxidation. Consequently, the optimized PdIr0.1/S-1 showed outstanding low-temperature activity for methane combustion (T50 = 276 °C) after aging and maintained long-term stability over 100 h under simulated exhaust conditions. Remarkably, the novel PdIr0.1/S-1 catalyst demonstrated significantly enhanced activity even after undergoing harsh hydrothermal aging at 750 °C for 16 h, significantly outperforming the conventional Pd/Al2O3 catalyst. This work provides valuable insights for designing efficient and durable MOC catalysts, addressing the critical issue of methane abatement.

Modular Access to Chiral Amines via Imine Reductase-Based Photoenzymatic Catalysis.

The development of catalysts serves as the cornerstone of innovation in synthesis, as exemplified by the recent discovery of photoenzymes. However, the repertoire of naturally occurring enzymes repurposed by direct light excitation to catalyze new-to-nature photobiotransformations is currently limited to flavoproteins and keto-reductases. Herein, we shed light on imine reductases (IREDs) that catalyze the remote C(sp3)-C(sp3) bond formation, providing a previously elusive radical hydroalkylation of enamides for accessing chiral amines (45 examples with up to 99% enantiomeric excess). Beyond their natural function in catalyzing two-electron reductive amination reactions, upon direct visible-light excitation or in synergy with a synthetic photoredox catalyst, IREDs are repurposed to tune the non-natural photoinduced single-electron radical processes. By conducting wet mechanistic experiments and computational simulations, we unravel how engineered IREDs direct radical intermediates toward the productive and enantioselective pathway. This work represents a promising paradigm for harnessing nature's catalysts for new-to-nature asymmetric transformations that remain challenging through traditional chemocatalytic methods.

Density functional theory study on the mechanism of water gas shift reaction catalyzed by molybdenum hexacarbonyl in aqueous solvent

The mechanism of the water gas shift reaction (WGSR) catalyzed by Mo(CO)6 in both gaseous and aqueous phases were analyzed using the density functional theory (DFT) method. This study indicates that aqueous phase slightly increased every energy barrier for each step along the reaction path. The turnover frequency (TOF) of the reaction was determined using the energy span model (ESM). The TOF value in the aqueous phase (2.48 × 10−16 s−1) is slightly lower than in the gas phase (6.08 × 10−16 s−1). Actually, the advantages of aqueous phase may be attributed to high solubility and concentration of H2O, CO, OH−. The study of temperature (300–900 K) on energy profile shows that the reaction rate of WGSR can be increased with the increase of temperature. This research filled the gap in understanding the mechanism for the WGSR in aqueous phase, provides a reasonable theoretical foundation for molybdenum-based catalysts development.

Balanced Mass Transfer and Active Sites Density in Hierarchical Porous Catalytic Metal–Organic Framework for Enhancing Redox Reaction in Lithium–Sulfur Batteries

Balanced Mass Transfer and Active Sites Density in Hierarchical Porous Catalytic Metal–Organic Framework for Enhancing Redox Reaction in Lithium–Sulfur Batteries

Self-assembly of NiFe-LDH@Ni3S2 sub-nanosheets catalyst for overall water splitting

The development of water splitting catalysts for generating high-purity hydrogen in large-scale is still facing challenges in terms of improving efficiency and stability. Herein, Ni3S2-coated NiFe layered double hydroxides sub-nanosheets with a hierarchical heterostructure (NiFe-LDH@Ni3S2) were prepared on nickel foam (NF) by a strategy of continuous hydrothermal synthesis. The introduction of S2− broke the hydrogen bonds between NiFe-LDH layers and separated into sub-nanosheets with a thickness of only about 1 nm, which enlarged the active areas of NiFe-LDH@Ni3S2/NF by a factor of 5.7. The coexisting charge channels Ni-O-Ni and Ni-S-Ni in the material enhanced the electrochemical activity, resulting in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) overpotentials as low as 179 mV and 116 mV at 10 mA cm−2 in 1.0 M KOH. Moreover, after a 50-hour chronopotentiometry test at 50 mA cm−2, the overpotential for OER and HER decreased only 0.013 V and 0.059 V, respectively. Furthermore, under the conditions of simulating industrial hydrogen production with an electrolyte of 6.0 M KOH and a temperature of 75 °C, after a 140-hour test for durability, the current density decreased only 0.75% at the cell voltage of 1.70 V.

Polymer-Supported Heterogeneous Fenton Catalysts for the Environmental Remediation of Wastewater

Materials based on polymer hydrogels have demonstrated potential as innovative Fenton catalysts for treating water. However, developing these polymer-supported catalysts with robust stability presents a significant challenge. This paper explores the development and application of polymer-supported heterogeneous Fenton catalysts for the environmental remediation of wastewater, emphasizing the enhancement of metal incorporation into catalysts for improved efficiency. The study begins with an introduction to the heterogeneous Fenton process and its relevance to wastewater treatment. It further delves into the specifics of polymer-supported heterogeneous Fenton catalysts, focusing on iron oxide, copper complexes/nanoparticles, and ruthenium as key components. The synthesis methods employed to prepare these catalysts are discussed, highlighting the innovative approaches to achieve substantial metal incorporation. Operational parameters such as catalyst dosage, pollutant concentration, and the effect of pH on the process efficiency are thoroughly examined. The catalytic performance is evaluated, providing insights into the effectiveness of these catalysts in degrading pollutants. Recent developments in the field are reviewed, showcasing advancements in catalyst design and application. The study also addresses the stability and reusability of polymer-supported heterogeneous Fenton catalysts, critical factors for their practical application in environmental remediation. Environmental applications are explored, demonstrating the potential of these catalysts in addressing various pollutants. The Conclusions offers future perspectives, underlining the ongoing challenges and opportunities in the field, and the importance of further research to enhance the efficacy and sustainability of polymer-supported heterogeneous Fenton catalysts for wastewater treatment.

Modulating the Activity and SO2 Resistance of α-Fe2O3 Catalysts for NH3-SCR of NOx via Crystal Facet Engineering.

The development of Fe-based catalysts for the selective catalytic reduction of NOx by NH3 (NH3-SCR of NOx) has garnered significant attention due to their exceptional SO2 resistance. However, the influence of different sulfur-containing species (e.g., ferric sulfates and ammonium sulfates) on the NH3-SCR activity of Fe-based catalysts as well as its dependence on exposed crystal facets of Fe2O3 has not been revealed. This work disclosed that nanorod-like α-Fe2O3 (Fe2O3-NR) predominantly exposing (110) facet performed better than nanosheet-like α-Fe2O3 (Fe2O3-NS) predominantly exposing (001) facet in NH3-SCR reaction, due to the advantages of Fe2O3-NR in redox properties and surface acidity. Furthermore, the results of the SO2/H2O resistance test at a critical temperature of 250 °C, catalytic performance evaluations on Fe2O3-NR and Fe2O3-NS sulfated by SO2 + O2 or deposited with NH4HSO4 (ABS), and systematic characterization revealed that the reactivity of ammonium sulfates on Fe2O3 catalysts to NO(+O2) contributed to their improved catalytic performance, while ferric sulfates showed enhancing and inhibiting effects on NH3-SCR activity on Fe2O3-NR and Fe2O3-NS, respectively; despite this, Fe2O3-NR showed higher affinity for SO2 + O2. This work set a milestone in understanding the NH3-SCR reaction on Fe2O3 catalysts in the presence of SO2 from the aspect of crystal facet engineering.

Advancements in bifunctional catalysts for unitized regenerative fuel cells: exploring polaronic conduction and heterostructure designs

This study investigates the development and performance evaluation of a bifunctional catalyst tailored for unitized regenerative fuel cells (URFCs), capable of facilitating both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in fuel cell and electrolyzer modes. The primary challenge addressed is the creation of electrocatalysts exhibiting high activity and corrosion resistance for oxygen reduction and water oxidation at the oxygen electrode. A novel catalyst structure based on La0.5Sr0.5Fe0.5Ti0.5O3(LSFT), i.e. LSFT/ZnO/LSFT with a thickness of ∼2 μ m, is explored within an environmentally friendly medium. This catalyst demonstrates superior performance characteristics, including reduced overpotential in HER and enhanced stability during oxygen/hydrogen evolution processes in neutral medium. This study identifies the formation of interfacial polarons and polaronic charge modulation resulting from the incorporation of ZnO in LSFT, leading to multifunctional OER/HER behavior. Notably, the proposed interfacial small polaron mechanism offers valuable insights into complex interfacial phenomena and holds promise for applications in diverse heterostructures involving layered 2D materials and transition metal oxides. Moreover, the robust LSFT/ZnO/LSFT catalyst exhibits exceptional stability, maintaining for 168 h of oxygen evolution at a constant potential of approximately 1.66 V for a current density of 1 A cm−2 in a neutral medium. These findings mark a significant advancement in URFC technology and present promising avenues for clean energy storage solutions.

Chemical bonding and electronic properties along Group 13 metal oxides

ContextThe present work provides a systematic theoretical analysis of the nature of the chemical bond in Al2O3, Ga2O3, and In2O3 group 13 cubic crystal structure metal oxides. The influence of the functional in the resulting band gap is assessed. The topological analysis of the electron density provides unambiguous information about the degree of ionicity along the group which is linearly correlated with the band gap values and with the cost of forming a single oxygen vacancy. Overall, this study offers a comprehensive insight into the electronic structure of metal oxides and their interrelations. This will help researchers to harness information effectively, boosting the development of novel metal oxide catalysts or innovative methodologies for their preparation.MethodsPeriodic density functional theory was used to predict the atomic structure of the materials of interest. Structure optimization was carried out using the PBE functional, using a plane wave basis set and the PAW representation of the atomic cores, using the VASP code. Next, the electronic properties were computed by carrying out single point calculations employing PBE, PBE + U functionals using VASP and also with PBE and the hybrid HSE06 functionals using the FHI-AIMS software. For the hybrid HSE06, the impact of the screening parameter, ω, and mixing parameter, α, on the calculated band gap has also been assessed.

Computation-Driven Rational Design of Self-Assembled Short Peptides for Catalytic Hydrogen Production.

Self-assembling peptides represent a captivating area of study in nanotechnology and biomaterials. This interest is largely driven by their unique properties and the vast application potential across various fields such as catalytic functions. However, design complexities, including high-dimensional sequence space and structural diversity, pose significant challenges in the study of such systems. In this work, we explored the possibility of self-assembled peptides to catalyze the hydrolysis of hydrosilane for hydrogen production using ab initio calculations and carried out wet-lab experiments to confirm the feasibility of these catalytic reactions under ambient conditions. Further, we delved into the nuanced interplay between sequence, structural conformation, and catalytic activity by combining modeling with experimental techniques such as transmission electron microscopy and nuclear magnetic resonance and proposed a dual mode of the microstructure of the catalytic center. Our results reveal that although research in this area is still at an early stage, the development of self-assembled peptide catalysts for hydrogen production has the potential to provide a more sustainable and efficient alternative to conventional hydrogen production methods. In addition, this work also demonstrates that a computation-driven rational design supplemented by experimental validation is an effective protocol for conducting research on functional self-assembled peptides.

Anion Structure Regulation of Cobalt Silicate Hydroxide Endowing Boosted Oxygen Evolution Reaction.

Transition metal silicates (TMSs) are attempted for the electrocatalyst of oxygen evolution reaction (OER) due to their special layered structure in recent years. However, defects such as low theoretical activity and conductivity limit their application. Researchers always prefer to composite TMSs with other functional materials to make up for their deficiency, but rarely focus on the effect of intrinsic structure adjustment on their catalytic activity, especially anion structure regulation. Herein, applying the method of interference hydrolysis and vacancy reserve, new silicate vacancies (anionic regulation) are introduced in cobalt silicate hydroxide (CoSi), named SV-CoSi, to enlarge the number and enhance the activity of catalytic sites. The overpotential of SV-CoSi declines to 301mV at 10mA cm-2 compared to 438mV of CoSi. Source of such improvement is verified to be not only the increase of active sites, but also the positive effect on the intrinsic activity due to the enhancement of cobalt-oxygen covalence with the variation of anion structure by density functional theory (DFT) method. This work demonstrates that the feasible intrinsic anion structure regulation can improve OER performance of TMSs and provides an effective idea for the development of non-noble metal catalyst for OER.

Quantitative investigation on microwave-accelerated fructose conversion via fluorescent thermometry

The use of microwave (MW) is promising for resolving energy-intensive problems that occur in carbohydrate bioconversion. To quantitatively investigate the mechanism of MW-accelerated reactions, the present study designs three carbon-based catalysts with distinct dielectric loss values (namely, SCS-SO3H, SCS-800-SO3H, MHCS-800-SO3H) for fructose hydrolysis. A fluorescence thermometer (Eu/Tb metal organic complex) was loaded on catalysts for in situ measurement of their localized temperature during MW heating. The combination of fluorescence experiments and theoretical modelling predicts that the temperature gradient between SCS-800-SO3H particles and bulk solvents reaches 26.10°C, which causes an 8.13-fold increase in reaction rate constants. Surprisingly, this speedup value is increased to 28.57 because of the thermal gradient up to 62.10°C when using MHCS-800-SO3H. In contrast, the MW-transparent SCS-SO3H exhibits no significant increase in the reaction rate. The quantitative elucidation of dominant roles of hot spots is promising for guiding the development of high-efficiency catalysts for MW-assisted heterogeneous reactions.

Porous Ruthenium-Tungsten-Zinc Nanocages for Efficient Electrocatalytic Hydrogen Oxidation Reaction in Alkali.

With the rapid development of anion exchange membrane technology and the availability of high-performance non-noble metal cathode catalysts in alkaline media, the commercialization of anion exchange membrane fuel cells has become feasible. Currently, anode materials for alkaline anion-exchange membrane fuel cells still rely on platinum-based catalysts, posing a challenge to the development of efficient low-Pt or Pt-free catalysts. Low-cost ruthenium-based anodes are being considered as alternatives to platinum. However, they still suffer from stability issues and strong oxophilicity. Here, we employ a metal-organic framework compound as a template to construct three-dimensional porous ruthenium-tungsten-zinc nanocages via solvothermal and high-temperature pyrolysis methods. The experimental results demonstrate that this porous ruthenium-tungsten-zinc nanocage with an electrochemical surface area of 116 m2 g-1 exhibits excellent catalytic activity for hydrogen oxidation reaction in alkali, with a kinetic density 1.82 times and a mass activity 8.18 times higher than that of commercial Pt/C, and a good catalytic stability, showing no obvious degradation of the current density after continuous operation for 10,000 s. These findings suggest that the developed catalyst holds promise for use in alkaline anion-exchange membrane fuel cells.

Efficient Homojunction/Heterojunction Photocatalyst via Integrating CsPbBr3 Quantum Dot Homojunction with TiO2 for Degradation of Organic Dyes.

A novel TiO2-CsPbBr3(Q) photocatalyst is proposed and rationally constructed, where CsPbBr3 perovskite quantum dots (QDs) of various sizes inside mesopore TiO2 (M-TiO2) are integrated. These perovskite QDs, generated in situ within M-TiO2, establish a type-II homojunction. Interestingly, a Z-scheme heterojunction is simultaneously formed at the interface between CsPbBr3 and TiO2. Due to the coexistence of the type-II homojunction and the Z-scheme heterojunction, photogenerated electrons are effectively transferred from TiO2 to CsPbBr3, thereby suppressing carrier recombination and thus enhancing the degradation of rhodamine B (RhB). Compared with pure CsPbBr3 and TiO2, TiO2-CsPbBr3(Q) shows significantly enhanced photocatalytic performance for RhB degradation. The degradation efficiency of RhB in the presence of the TiO2-CsPbBr3(Q) attains 97.7% in 5 min under light illumination, representing the highest efficiency observed among photocatalysts based on TiO2. This study will facilitate the development of superior semiconductor catalysts for photocatalytic applications.

Facilitating the dry reforming of methane with interfacial synergistic catalysis in an Ir@CeO2−x catalyst

The dry reforming of methane provides an attractive route to convert greenhouse gases (CH4 and CO2) into valuable syngas, so as to resolve the carbon cycle and environmental issues. However, the development of high-performance catalysts remains a huge challenge. Herein, we report a 0.6% Ir/CeO2−x catalyst with a metal-support interface structure which exhibits high CH4 (~72%) and CO2 (~82%) conversion and a CH4 reaction rate of ~973 μmolCH4 gcat−1 s−1 which is stable over 100 h at 700 °C. The performance of the catalyst is close to the state-of-the-art in this area of research. A combination of in situ spectroscopic characterization and theoretical calculations highlight the importance of the interfacial structure as an intrinsic active center to facilitate the CH4 dissociation (the rate-determining step) and the CH2* oxidation to CH2O* without coke formation, which accounts for the long-term stability. The catalyst in this work has a potential application prospect in the field of high-value utilization of carbon resources.

Efficient reverse water gas shift reaction at low temperatures over an iron supported catalyst under an electric field

The development of high-performance Fe-based catalysts is attractive because Fe is a cost-effective and earth-abundant element. Application of an external electric field and an appropriate catalytic support to an Fe-based catalyst enabled the reverse water–gas shift reaction to proceed with high activity, selectivity, and durability even at the low temperature of 423 K. The Fe-supported catalyst showed superior CO selectivity (≈ 100%) compared to the Co- or Ni-supported catalyst. The apparent activation energy (5.9 kJ mol−1) over the Fe/Ce0.4Al0.1Zr0.5O2 catalyst under an electric field was much lower than that without an electric field (61.4 kJ mol−1).

Co–B supported on waxberry-like hierarchical porous carbon microspheres: An efficient catalyst for hydrogen generation via sodium borohydride hydrolysis

Rapid release of hydrogen at ambient condition is highly favorable and is necessary for fuel cell power generation on-demand. Hydrolysis of hydrides offers such advantage with sodium borohydride (NaBH4) as a representative exemplar. Despite with exceptionally high hydrogen content, the hydrolysis kinetics of NaBH4 is sluggish in the absence of catalyst. Co–B alloy has generally been employed as effective catalyst in the hydrolysis of borohydrides. However, Co–B particles are prone to agglomeration during the reaction, reducing the activity and durability of the catalyst. In this work, waxberry-like hierarchical porous carbon microspheres (HPCMs) were successfully prepared and were used as carriers to support Co–B particles to form the Co–B/HPCMs catalyst. The effects of HPCMs with different nitrogen contents in Co–B/HPCMs on the catalytic dehydrogenation rate of NaBH4 hydrolysis were systematically investigated. The experimental results showed that Co–B/HPCM-2 exhibited excellent catalytic activity in the hydrolysis of NaBH4 at 298 K, with a low activation energy of 43.3 kJ ·mol−1 and a high hydrogen generation rate of 3083.1 mlH2·min−1·g−1. Moreover, after five consecutive cycles, its catalytic activity maintained at 91.7 % of the initial catalytic activity, displaying satisfactory cycling performance. The findings obtained from this study are expected to expand a novel path for the development of efficient Co-based catalysts in heterogeneous catalytic reactions.

Aquivion-based spray freeze-dried composite materials for the cascade production of γ-valerolactone.

The development of multifunctional catalysts is a necessary step to effectively carry out cascade reactions, such as that from furfural to γ-valerolactone. This research effort faces the challenge posed by the intrinsic limit of how many kinds of catalytic sites a single material can bear. In this work, the application of Spray-Freeze Drying (SFD) as a synthetic technique for the preparation of a wide range of composite multi-functional catalysts is reported. Herein we show that by the proper combination of Aquivion as a highly active Brønsted acid catalyst and metal oxides as Lewis acids (LAS) enable to achieve highly unique efficient and effective dual acid composite catalysts that are able to carry out the cascade reaction from furfural to γ-valerolactone. The dual catalytic system comprised of Aq/ZrO2 with 30% polymer content prepared via spray-freeze drying exhibited GVL yields of 25% after only 2 h at 180 °C and a remarkably high productivity of 4470 µmolGVL gCat-1 h-1, one of the highest reported results. Mechanistic studies based on experimental and advanced characterisation and spectroscopic techniques, such as, SEM, TEM, 15N MAS NMR and 19F MAS NMR indicate that activity arises from the proper tuning of BAS/LAS acidic properties.

Insight of hydrogen evolution reaction in slab SnO2 loaded with transition metal atoms

Abstract The utilization of hydrogen energy has emerged as a promising solution for clean and sustainable energy sources. The development of cost-effective catalysts with high activity and stability is crucial for efficient hydrogen production. In this work, we investigated the hydrogen evolution reaction catalytic activity of single transition metal atom (TM = V, Cr, Mn, Fe, Co, Ni) on slab SnO2 by using density functional theory. Our results revealed that the catalytic activity of the slab SnO2 can be significantly enhanced by loading the transition atom. By calculating the Gibbs free energies and exchange current densities in different adsorption configurations of TM-SnO2, single-atom catalyst of Mn-loaded single-atom catalyst exhibits excellent catalytic performance, characterized by a low Gibbs free energy barrier (-0.05 eV). Introducing a transition metal on the SnO2 surface breaks its local symmetry, while the strong coupling between the metal and H atoms enhances catalytic performance. The synergetic effect of symmetry breaking and metal-H interaction boosts overall catalytic activity. This work not only proposes a novel non-platinum HER catalyst based on SnO2 but also lays a solid foundation for future applications of SnO2-based catalysts.