Catalytic Reduction Research Articles

Enhanced denitrification performance of Mo/Mn co-doped 5 %Fe/TiO2 catalysts via citric acid-assisted impregnation

This study investigates the denitrification performance of Fe5Mn3Mo3/TiO2 catalysts prepared using citric acid-assisted impregnation (CA) and conventional impregnation (IM) methods in the context of NH3-selective catalytic reduction (SCR) reaction. Specifically, the influence of citric acid quantity on the catalytic activity is studied, with a special emphasis on Fe5Mn3Mo3/TiO2-0.5CA variant. Our results demonstrate that Fe5Mn3Mo3/TiO2-0.5CA exhibits superior low-temperature activity and prolonged stability compared to the conventional impregnation method. Remarkably, operating temperature window based on 80 % denitrification activity is T80 = 190–405 °C. Furthermore, the Fe5Mn3Mo3/TiO2-0.5CA maintains a noteworthy 98 % NO conversion at 300 °C for a duration of 100 hours. The excellent performance is attributed to the highly dispersed nature of the active species, the large specific surface area, the low apparent activation energy, and a robust interaction between the active components and the substrate. XPS analysis reveals a significantly higher Oα/(Oα+Oβ) ratio for Fe5Mn3Mo3/TiO2-0.5CA, underscoring the effectiveness of citric acid modification in promoting the formation of Fe2+ species. This research provides valuable insights into the design and optimization of catalysts for efficient denitrification processes.

Biogenic synthesis and characterization of zinc oxide nanoparticles for effective and rapid catalytic reduction of 4-nitrophenol

This paper discusses the biogenic synthesis of zinc oxide (ZnO) nanoparticles by using aqueous solutions of zinc acetate dihydrate and Ocimum tenuiflorum leaf extract. Field emission scanning electron microscopy (FE-SEM) confirms the formation of fine ZnO aggregates. Crystallographic structure and functional group of the nanoparticles are determined by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) techniques. UV–visible and fluorescence spectroscopies are employed to assess optical behaviour of ZnO nanoparticles.The ZnO nanoparticles show nearly 100 % catalytic efficiency in the sodium borohydride (NaBH4)-mediated reduction of 4-nitrophenol within 60 s. Also, the catalyst can be reused for five cycles without losing 100 % regeneration efficiency. This study demonstrates that the prepared ZnO nanoparticles can effectively detoxify 4-nitrophenol from an aqueous solution.

Enhancing acidity of Ru/Ce/ZrO2 bifunctional catalysts for promoting N2 selectivity in selective catalytic oxidation of NH3

To solve the problem of low N2 selectivity of Ru/Ce/ZrO2 (R/C/Z) catalysts in NH3 selective catalytic oxidation (NH3-SCO) reaction, herein ZrO2 supports were treated with sulfuric acid and its effects on NH3-SCO performance were investigated systematically. The results showed that Ru/Ce/ZrO2-10S (R/C/Z-10S) catalyst, in which the mass ratio of sulfuric acid to ZrO2 was 10 %, exhibited N2 selectivity of 95.7 % at 350 °C, that was significantly higher than R/C/Z catalyst (57.8 %). NH3-TPD tests indicated that sulfate treatment of ZrO2 supports in R/C/Z catalysts led to more abundant acidic sites on catalyst surface, which was in favor of enhancing NH3 adsorption capacity remarkably. But when mass ratio of sulfuric acid to ZrO2 increased up to 20 %, an aggregation of metal oxides on the surface of R/C/Z-20S catalyst could be observed clearly, which might impose an adverse impact on NH3-SCO performance. In-situ DRIFTS results revealed that, compared to R/C/Z catalyst, there were much more Brönsted acid sites on the surface of R/C/Z-10S catalyst, and the corresponding NH3 species on acidic sites could be consumed quickly in intermediate reactions. More importantly, amide (-NH2) species rather than imide (-NH) and nitrosyl (-HNO) species, were the majority on the surface of R/C/Z-10S catalyst, implying that there might be a suppressing effect on further dehydrogenation of -NH2 species into -NH species owning to sulfate treatment of ZrO2 supports in R/C/Z catalysts. Therefore, internal selective catalytic reduction (i-SCR) mechanism rather than -NH mechanism played a vital role in NH3-SCO reaction over R/C/Z-10S catalyst.

Numerical Simulation of the OFA Effect on Combustion in a 600 MWe Boiler with Centrally Fuel Rich Burners

ABSTRACT With the rapid development of renewable energy, the traditional coal-fired power generation plays an important role in peak regulation, which requires the boilers to operate at low load or even ultra-low load. In order to investigate the effect of over-fire air (OFA) ratio on the flow, temperature and component concentration distribution and the furnace exit parameters for utility boilers at ultra-low loads, a 600 MWe utility boiler with centrally fuel rich (CFR) burner technology is taken as the object of study, and numerical simulations are carried out for five operating conditions with different OFA ratios (0%–40%) at 25% of the boiler’s maximum continuous rating (BMCR) load. The results show that no obvious high-temperature region is formed in the furnace and the flow field distribution in the furnace exit area is not conducive to the stable combustion of pulverized coal when the OFA ratio is 0% and 10%. When the OFA ratio is 30%, the area of the high-temperature region in the furnace reaches its maximum. When the OFA ratio is 40%, the furnace exit NO concentration is only 94.54 ppm. With the increase of the OFA ratio from 0% to 40%, the temperature of the flue gas at the furnace exit decreases by more than 100 K, which may affect the stable operation of the Selective Catalytic Reduction (SCR) denitrification equipment. Taking into consideration the flow in the furnace, the combustion, the NO x emission, and other factors, the recommended OFA ratio is 20% ~30%.

Recent Advances in SCR Systems of Heavy-Duty Diesel Vehicles—Low-Temperature NOx Reduction Technology and Combination of SCR with Remote OBD

Heavy-duty diesel vehicles are a significant source of nitrogen oxides (NOx) in the atmosphere. The Selective Catalytic Reduction (SCR) system is a primary aftertreatment device for reducing NOx emissions from heavy-duty diesel vehicles. With increasingly stringent NOx emission regulations for heavy-duty vehicles in major countries, there is a growing focus on reducing NOx emissions under low exhaust temperature conditions, as well as monitoring the conversion efficiency of the SCR system over its entire lifecycle. By reviewing relevant literature mainly from the past five years, this paper reviews the development trends and related research results of SCR technology, focusing on two main aspects: low-temperature NOx reduction technology and the combination of SCR systems with remote On-Board Diagnostics (OBD). Regarding low-temperature NOx reduction technology, the results of the review indicate that the combination of multiple catalytic shows potential for achieving high conversion efficiency across a wide temperature range; advanced SCR system arrangement can accelerate the increase in exhaust temperature within the SCR system; solid ammonium and gaseous reductants can effectively address the issue of urea not being able to be injected under low-temperature exhaust conditions. As for the combination of SCR systems with remote OBD, remote OBD can accurately assess NOx emissions from heavy-duty vehicles, but it needs algorithms to correct data and match the emission testing process required by regulations. Remote OBD systems are crucial for detecting SCR tampering, but algorithms must be developed to balance accuracy with computational efficiency. This review provides updated information on the current research status and development directions in SCR technologies, offering valuable insights for future research into advanced SCR systems.

A promising sustainable green nanosilver formula for p-nitrophenol and methylene blue remediation from wastewater

In an attempt to create wastewater treatment “green” techniques that are both economically feasible and sustainable without using any dangerous chemicals, barley grain (Hordeum vulgare L.) water extract was used to phyto-synthesize silver nanoparticles (Ag°). Barley grains served as a natural reductant and stabilizer at the same time. The role of different synthesis conditions and their effect on the efficiency of the green synthesis process were studied and confirmed with characterization using several techniques (UV–vis, SEM, EDX, sizing distribution, and FTIR). The Ag°9 formula catalytic reduction was inspected against p-nitrophenol (PNP) and methylene blue (MB) as a model of nitroaromatic components and dyes, respectively. The removal studies were conducted using the target pollutants in a single or mixed liquid state. Remarkably, the Ag°9 particle size was around 20 nm, and its final concentration in the current formula was 2.2 × 10−7 mol L−1. The adsorption mechanism of the PNP and MB was pseudo-second order. The good fit with the pseudo-second-order kinetic model suggests that chemisorption occurs in the sorption process. The formula catalytic activity to remove PNP and MB was 99 and 66% at levels 60 and 500 µL from the Ag°9 formula, respectively, within less than 5 min.

Photothermal Catalytic Reduction and Bone Tissue Engineering Towards a Three-in-One Therapy Strategy for Osteosarcoma.

Osteosarcoma is one of the most dreadful bone neoplasms in young people, necessitating the development of innovative therapies that can effectively eliminate tumors while minimizing damage to limb function. An ideal therapeutic strategy should possess three essential capabilities: antitumor effects, tissue-protective properties, and the ability to enhance osteogenesis. In this study, self-assembled Ce-substituted molybdenum blue (CMB) nanowheel crystals are synthesized and loaded onto 3D-printed bioactive glass (CMB@BG) scaffolds to develop a unique three-in-one treatment approach for osteosarcoma. The CMB@BG scaffolds exhibit outstanding photothermally derived tumor ablation within the near-infrared-II window due to the surface plasmon resonance properties of the CMB nanowheel crystals. Furthermore, the photothermally synergistic catalytic effect of CMB promotes the rapid scavenging of reactive oxygen species caused by excessive heat, thereby suppressing inflammation and protecting surrounding tissues. The CMB@BG scaffolds possess pro-proliferation and pro-differentiation capabilities that efficiently accelerate bone regeneration within bone defects. Altogether, the CMB@BG scaffolds that combine highly efficient tumor ablation, tissue protection based on anti-inflammatory mechanisms, and enhanced osteogenic ability are likely to be a point-to-point solution for the comprehensive therapeutic needs of osteosarcoma.

Highly Efficient Electrospun Silver Decorated Graphene Oxide Nanocomposites on Poly(vinylidene fluoride) (PVDF@GO-Ag) Hybrid Membrane for Reduction of 4-Nitrophenol.

Graphene oxide-silver poly(vinylidene fluoride) membranes (PVDF@GO-Ag) were successfully synthesized by the electrospinning method, which exhibited a high catalytic activity using the hydrogenation of 4-nitrophenol (4-NP) as a model reaction in a batch reaction study. The hybrid membranes doped with 1 wt% GO and 2 wt% Ag (PVDF-1-2) exhibited the most desired performance for the catalytic reduction of 4-NP. Importantly, PVDF-1-2 exhibited excellent cycling stability in 10 catalytic cycle tests and was highly amenable to separation. This property effectively addresses the significant challenges associated with the practical application of nanocatalysts. Furthermore, density-functional theory (DFT) calculations have demonstrated that the GO-Ag nanocomposites exhibit the strongest adsorption capacity for 4-NP- when a specific ratio of GO and Ag is achieved, accompanied by the loading of Ag nanoclusters onto GO. Additionally, the study demonstrated that an increase in temperature significantly accelerated the reaction rate, in line with the van't Hoff rule. This study provides an effective and environmentally friendly solution for the treatment of 4-NP in wastewater.

Highly Efficient and Robust Platinum Nanocluster Catalyst Mediated by Polyamine Amidine‐Decorated Mesoporous Polymer Beads

AbstractPlatinum nanoclusters (PtNCs) are promising in catalysis due to their large specific surface area and unique physicochemical properties. Here, ultrasmall and uniform PtNCs are facilely synthesized with the mediation of amidine‐functionalized polyamines patched on mesoporous poly(divinylbenzene‐4‐vinylbenzyl chloride) beads. When each ligand patch has 14 amidines, ultrafine PtNCs (with the size as low as 1.1±0.1 nm) are formed as a result of several factors: deprotonated amidines (carbenes) strongly passivate on Pt atoms, amidines act as co‐stabilizers along with weak polyamine ligands, and PtNCs are confined to discrete ligand patches. When one ligand patch contains 9.3 amidines, the resulting PtNCs (1.7±0.3 nm) reach the highest turnover frequency of 536 h−1 for the catalytic reduction of 4‐nitrophenol in a batch reaction. This catalyst remains rather stable in a continuous flow test as a 4‐nitrophenol conversion of over 95 % is still achieved after running consecutively for 10 h.

New metallophthalocyanine (M: Ni(II) and Fe(II)) complexes as efficient catalysts for transfer hydrogenation of various ketones

Hydrogen transfer reduction methods are attracting increasing attention from synthetic chemists in view of their operational simplicity. Therefore, the novel Ni(II) and Fe(II) tetra substituted metallophthalocyanines containing resorcinol and guaiacol groups were synthesized using microwave irradiation and characterized via elemental analysis, UV-Vis and FT-IR spectroscopy, and TGA. The comparison of the catalytic features of phthalocyanine based on metals is discussed in detail. These phthalocyanine-complexes were tested in transfer hydrogenation (TH) of ketones in the existence of KOH, utilizing 2-propanol as a hydrogen source. Examination of different carbonyl substrates revealed that Nickel (II) phthalocyanine, (Ni2) complex was a remarkable catalyst for the catalytic reduction of acetophenones (1.0 mol % of catalyst, 99 % conversion). Furthermore, we have discovered that the catalytic characteristics of this class of molecules are significantly influenced by both steric and electronic variables.

Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst

Catalysts for the selective catalytic reduction (NOX SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NOX SCR shows various SCR efficiencies. In the current work, an SCR catalyst developed from the sludge produced with Fe/C micro-electrolysis Fenton technology (MEF) in wastewater treatment was investigated, taking into account various sludge compositions, Fe/C ratios, and contaminant contents. It was found that, at about 300 °C, the NOX removal rate could reach 100% and there was a wide decomposition temperature zone. The effect of individual components of electroplating sludge, i.e., P, Fe and Ni, on NOX degradation performance of the obtained solids was investigated. It was found that the best effect was achieved when the Fe/P was 8/3 wt%, and variations in the Ni content had a limited effect on the NOX degradation performance. When the Fe/C was 1:2 and the Fe/C/P was 1:2:0.4, the electroplating sludge formed after treatment with Fe/C MEF provided the best NOX removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NOX. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P effectively reduces the catalytic reaction temperature, and the formation of phosphate promotes the generation of adsorbed oxygen, which in turn contributes to improvements in catalytic efficiency. Therefore, our work suggests that controlling the composition in the sludge is an efficient way to modulate SCR catalysis, providing a bridge from contaminant-bearing waste to efficient catalyst.

Excellent performance of Ce doped CoMn2O4/TiO2 catalyst in NH3-SCR of NOx under H2O&SO2 conditions

Mn-based catalysts have become a research hotspot for low-temperature NH3-SCR, and the improvement of anti-SO2 poisoning performance is crucial to promote their industrial application for NH3 selective catalytic reduction of NOx. In this work, the CoMn2O4/Ce-TiO2 catalyst was able to maintain 95 % NOx conversion even in the presence of 10 vol% H2O+50 ppm SO2 for 24 h at 250 °C.The excellent performance was attributed to the large mesoporous structure, specific surface area, and the enhancement of acid and redox properties associated with the catalysts. The Ce doped CoMn2O4/Ce-TiO2 catalyst maintained Mn3+, Mn4+ and Co3+ in high concentrations on the surface, which improved the lattice oxygen mobility, and the electron transfer and interaction. The presence of more Ce4+ provided higher SCR activity due to the strong oxygen storage migration and also release ability. The reaction process of NH3-SCR for NOx removal on the surface of CoMn2O4/Ce-TiO2 catalyst mainly followed the Eley-Rideal (E-R) mechanism. The NH3 adsorbed on the catalyst surface reacted mainly with NO/NO2 species, even under H2O&SO2. The E-R reaction mechanism on the surface of CoMn2O4/Ce-TiO2 catalyst was less restricted by the inhibition of H2O&SO2. This is one of the primary reasons for the superior anti-sulfur toxicity performance of the catalyst. This work opens a new avenue for the design of efficient and environmentally friendly NH3-SCR catalysts with good application prospects.

Hot Electrons Induced by Localized Surface Plasmon Resonance in Ag/g-C3N4 Schottky Junction for Photothermal Catalytic CO2 Reduction.

Converting carbon dioxide (CO2) into high-value-added chemicals using solar energy is a promising approach to reducing carbon dioxide emissions; however, single photocatalysts suffer from quick the recombination of photogenerated electron-hole pairs and poor photoredox ability. Herein, silver (Ag) nanoparticles featuring with localized surface plasmon resonance (LSPR) are combined with g-C3N4 to form a Schottky junction for photothermal catalytic CO2 reduction. The Ag/g-C3N4 exhibits higher photocatalytic CO2 reduction activity under UV-vis light; the CH4 and CO evolution rates are 10.44 and 88.79 µmol·h-1·g-1, respectively. Enhanced photocatalytic CO2 reduction performances are attributed to efficient hot electron transfer in the Ag/g-C3N4 Schottky junction. LSPR-induced hot electrons from Ag nanoparticles improve the local reaction temperature and promote the separation and transfer of photogenerated electron-hole pairs. The charge carrier transfer route was investigated by in situ irradiated X-ray photoelectron spectroscopy (XPS). The three-dimensional finite-difference time-domain (3D-FDTD) method verified the strong electromagnetic field at the interface between Ag and g-C3N4. The photothermal catalytic CO2 reduction pathway of Ag/g-C3N4 was investigated using in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS). This study examines hot electron transfer in the Ag/g-C3N4 Schottky junction and provides a feasible way to design a plasmonic metal/polymer semiconductor Schottky junction for photothermal catalytic CO2 reduction.

Zirconium Hydride Catalysis Initiated by Tetrabutylammonium Fluoride.

In our drug discovery campaigns to target the oncogenic drivers of cancers, the demand for a chemoselective, stereoselective and economical synthesis of chiral benzylamines drove the development of a catalytic zirconium hydride reduction. This methodology uses the inexpensive, bench stable zirconocene dichloride, and a novel tetrabutylammonium fluoride activation tactic to catalytically generate a metal hydride under ambient conditions. The diastereo- and chemoselectivity of this reaction was tested with the preparation of key intermediates from our discovery programs and in the scope of sulfinyl ketimines and carbonyls relevant to medicinal chemistry and natural product synthesis. A preliminary mechanistic investigation conducted into the role of tetrabutylammonium fluoride indicates that formation of a zirconocene fluoride occurs to initiate catalysis. The implications of this convenient activation approach may provide expanded roles for zirconium hydrides in catalytic transformations.

Low-silica chabazite zeolites for NOx reduction: Tailoring the active center of Cu2+-2Z and [Cu(OH)]+-Z through the regulation of CHA-cages opening

Low-silica chabazite (CHA) catalysts with varying configurations of Cu2+-2Z and [Cu(OH)]+-Z active centers are developed through the regulation of the opening of CHA-cages. The catalysts are subsequently applied to the selective catalytic reduction of NOx by NH3 (NH3-SCR) reactions. A series of characterizations and performance evaluations indicate that the density of [Cu(OH)]+-Z in eight-member rings (8MRs) is positively correlated with low-temperature performance. Moreover, the presence of partial Cu2+-2Z in six-member rings (6MRs) enhances activity and tolerance at high temperatures. The residual K+ ions in the CHA-cages after NH4+ exchange are retained in the 6MRs. Density functional theory calculations demonstrate that the residual K+ ions stabilize the 6MRs structure, ensuring the entry and stable presence of the active Cu2+-2Z centers. In situ analysis reveals the reaction intermediates involved in the NH3-SCR process on representative catalysts. These findings can further elucidate the active centers of CHA-type catalysts and guide the design of commercial catalysts.

Challenges and Perspectives of Environmental Catalysis for NO x Reduction.

Environmental catalysis has attracted great interest in air and water purification. Selective catalytic reduction with ammonia (NH3-SCR) as a representative technology of environmental catalysis is of significance to the elimination of nitrogen oxides (NO x ) emitting from stationary and mobile sources. However, the evolving energy landscape in the nonelectric sector and the changing nature of fuel in motor vehicles present new challenges for NO x catalytic purification over the traditional NH3-SCR catalysts. These challenges primarily revolve around the application limitations of conventional industrial NH3-SCR catalysts, such as V2O5-WO3(MoO3)/TiO2 and chabazite (CHA) structured zeolites, in meeting both the severe requirements of high activity at ultralow temperatures and robust resistance to the wide array of poisons (SO2, HCl, phosphorus, alkali metals, and heavy metals, etc.) existing in more complex operating conditions of new application scenarios. Additionally, volatile organic compounds (VOCs) coexisting with NO x in exhaust gas has emerged as a critical factor further impeding the highly efficient reduction of NO x . Therefore, confronting the challenges inherent in current NH3-SCR technology and drawing from the established NH3-SCR reaction mechanisms, we discern that the strategic manipulation of the properties of surface acidity and redox over NH3-SCR catalysts constitutes an important pathway for increasing the catalytic efficiency at low temperatures. Concurrently, the establishment of protective sites and confined structures combined with the strategies for triggering antagonistic effects emerge as imperative items for strengthening the antipoisoning potentials of NH3-SCR catalysts. Finally, we contemplate the essential status of selective synergistic catalytic elimination technology for abating NO x and VOCs. By virtue of these discussions, we aim to offer a series of innovative guiding perspectives for the further advancement of environmental catalysis technology for the highly efficient NO x catalytic purification from nonelectric industries and motor vehicles.

Activation of Bi2MoO6/Zn0.5Cd0.5S charge transfer through interface chemical bonds and surface defects for photothermal catalytic CO2 reduction

The photocatalytic reduction of CO2 to high-value fuels has been proposed as a solution to the energy crisis caused by the depletion of energy resources. Despite significant advancements in photocatalytic CO2 reduction catalyst development, there are still limitations such as poor CO2 adsorption/activation and low charge transfer efficiency. In this study, we employed a defect-induced heterojunction strategy to construct atomic-level interface Cd-O bonds and form Bi2MoO6/Zn0.5Cd0.5S heterojunctions. The sulfur vacancies (VS) formed in Bi2MoO6/Zn0.5Cd0.5S acted as activation sites for CO2 adsorption. While the interfacial stability provided by the Cd-O bonds served as an electron transfer channel that facilitated the movement of electrons from the interface to the catalytic site. The VS and Cd-O bonds simultaneously influence the distribution of charge, inducing the creation of an interface electric field that facilitates the upward displacement of the center of the d-band. This enhances the adsorption of reaction intermediates. The optimized Bi2MoO6/Zn0.5Cd0.5S heterostructure exhibited high selectivity and stability of photoelectrochemical properties for CO, generating 42.97 μmol⋅g−1⋅h−1 of CO, which was 16.65-fold higher than Zn0.5Cd0.5S under visible light drive. This research provides valuable insights for designing photocatalyst interfaces with improved CO2 adsorption conversion efficiency.

In-Situ investigation of the catalytic hydrogenation reaction of 4-nitrothiophenol by using single Pt@Au nanowires as a new platform

Investigating the kinetics and mechanisms of catalytic hydrogenation reaction is important for fundamental research and chemical engineering, especially at single nanowire/nanoparticle level. In this work, we constructed a dual-functional single Pt@Au nanowire (Pt@Au NW) reaction platform, which was used for in-situ monitoring the p-nitrothiophenol (4-NTP) catalytic reduction process by using surface-enhanced Raman scattering (SERS) and UV–vis spectroscopy. The conversion of reactants and intermediates as well as the product generation during the reaction process were analyzed carefully, and the influencing factors of temperature and light were also discussed. Moreover, the density functional theory (DFT) was used to further investigate the effect of the single Pt@Au NW on catalytic hydrogenation reaction of 4-NTP. The results show that the single Pt@Au NW can be a good platform for in-situ monitoring catalytic hydrogenation reaction of 4-NTP with excellent catalytic activity, high stability, and good reproducibility, and clarified that trans-dimercaptoazobenzene (trans-DMAB) intermediates were produced that are further converted to the p-aminothiophenol (4-ATP). The work will not only give researchers new insights into the combination of the single nanowire/nanoparticle with spectroscopic techniques, but may also inspire further in-depth studies of multifunctional catalysts for catalytic hydrogenation reaction at single entity level.

Promoting photothermal catalytic N2 reduction through dynamic mass transfer and accelerated charge transfer dynamics

The effective adsorption and mass transfer of N2 at the catalytic active site, along with efficient photogenerated charge transfer at the interface are the prerequisites for the photothermal catalysis N2 reduction. Here, the hydrophobic-hydrophilic biphasic heterojunction Bi2WO6/ Bi2Sn2O7 (BWSO-20) was prepared by solvothermal method, and a strong interfacial internal electric field (IEF) was formed. The effects of N2 dynamic mass transfer and interface charge transfer kinetics on the performance of photothermal catalytic N2 reduction (PTC-NRR) was investigated. The results from in-suit DRIFTS, DFT, and molecular dynamics simulations (MD) indicated that a biphasic structure enhanced the dynamic mass transfer of N2 in the hydrophobic phase (BSO) and H2O in the hydrophilic phase (BWO) simultaneously. Additionally, the IEF that accelerates the transfer kinetics of photo-generated charges. Therefore, more photo-generated electrons and holes could transfer to the surface of the hydrophobic/hydrophilic phase catalyst and undergo redox semi-reactions with N2 and H2O. The PTC-NRR reached 366.1 μmoL·g−1 when using BWSO-20 without adding sacrificial agent. This work provides a new way to achieve efficient photothermal N2 reduction based on the interfacial charge transfer kinetics accelerated by the interfacial internal electric field and the dynamic mass transfer enhanced by hydrophobic – hydrophilic two-phase heterojunction.

Effect of Bipyridines on Catalytic Oxygen Reduction by Oxamidato‐Bridged Dicopper(II) Complexes

ABSTRACTThe oxygen reduction reaction (ORR) has a crucial impact on the energy conversion efficiency and the performance of fuel cells, it is urgent to deliver low‐cost efficient ORR catalysts for the aim to scale up the utilization of fuel cells. In this study, three oxamidate copper(II) complexes [Cu2(trans‐L)(H2O)2(ClO4)2]·2H2O (Cuox), [Cu2(cis‐L)(bpy)(ClO4)2]·CH3OH (Cuoxbpy), and [Cu2(cis‐L)(mebpy)(ClO4)](ClO4) (Cuoxmebpy) (L = N,N–bis(2–pyridylmethyl)oxamide, bpy = 2,2′–bipyridine, and mebpy = 4,4′–dimethyl–2,2′–bipyridine) were prepared and characterized. The configuration of L varied from the trans form to the cis form as the bipyridines were introduced to the dicopper complex. The redox properties of three oxamidate copper(II) complexes and their catalytic activities for the ORR were studied in neutral aqueous solutions. The ORR onset potentials by Cuox, Cuoxbpy, and Cuoxmebpy were 0.417, 0.502, and 0.481 versus RHE, respectively. Three complexes homogeneously catalyzed the ORR to predominantly generate H2O2. A bimolecular catalytic pathway was proposed for the ORR mediated by Cuox, whereas a single‐molecular pathway was by Cuoxbpy and Cuoxmebpy. This work demonstrated that oxamidate metal complexes are promising ORR catalyst candidates provided that their electronic structures are appropriately tuned by altering the substituent on the organic ligands.