Synergistic Active Sites Research Articles

0D–2D multifunctional bimetallic MOF derivative-MXene heterojunction for high areal capacity lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted much attention due to their high specific capacity. However, at high loads and rates, the polysulfides conversion rate and ion transport of batteries are slow, limiting their commercialization. This work reports zero-dimensional (0D) bimetallic MOF derivatives grown in situ on two-dimensional (2D) MXene by electrostatic adsorption (FeCo@Ti3C2). The 0D bimetallic structure effectively avoids the stacking of MXene while providing a dual catalytic site for polysulfides. The 2D structure of MXene also provides a large number of pathways for the rapid diffusion of lithium ions. This 0D–2D heterostructured heterogeneous catalyst with bimetallic synergistic active sites efficiently immobilizes and catalyzes polysulfides, providing a fast charge transfer pathway for the electrochemical reaction of lithium polysulfides. The Li-S battery with this multifunctional 0D–2D heterojunction structure catalyst has outstanding high rate capacity (703 mAh g−1 at 4 C at room temperature and 555 mAh g−1 at 2 C at 0 °C), fascinating capacity at high load (5.5 mAh cm−2 after 100 cycles at a high sulfur content of 8.2 mg cm−2). The study provides new ideas for the commercialization of high-efficiency Li-S batteries.

Sustainable Electrosynthesis of N,N-Dimethylformamide via Relay Catalysis on Synergistic Active Sites.

Electrified synthesis of high-value organonitrogen chemicals from low-cost carbon- and nitrogen-based feedstocks offers an economically and environmentally appealing alternative to traditional thermocatalytic methods. However, the intricate electrochemical reactions at electrode surfaces pose significant challenges in controlling selectivity and activity, especially for producing complex substances such as N,N-dimethylformamide (DMF). Herein, we tackle this challenge by developing relay catalysis for efficient DMF production using a composite WO2-NiOOH/Ni catalyst with two distinctive active sites. Specifically, WO2 selectively promotes dimethylamine (DMA) electrooxidation to produce strongly surface-bound (CH3)2N*, while nearby NiOOH facilitates methanol electrooxidation to yield more weakly bound *CHO. The disparity in binding energetics of the key C- and N-intermediates expedites C-N coupling at the WO2-NiOOH interface. In situ infrared spectroscopy with isotope-labeling experiments, quasi-in situ electron paramagnetic resonance trapping experiments, and electrochemical operating experiments revealed the C-N coupling mechanism and enhanced DMF-synthesis selectivity and activity. In situ X-ray absorption spectroscopy (XAS) and postreaction transmission electron microscopy (TEM) studies verified the stability of WO2-NiOOH/Ni during extended electrochemical operation. A Faradaic efficiency of ∼50% and a production rate of 438 μmol cm-2 h-1 were achieved at an industrially relevant current density of 100 mA cm-2 over an 80 h DMF production period. This study introduces a new paradigm for developing electrothermo relay catalysis for the sustainable and efficient synthesis of valuable organic chemicals with industrial potential.

Tunable Ptδ+/Pt0 sites by highly dispersed defected TiO2 for efficient catalytic methylcyclohexane dehydrogenation

Dehydrogenation reaction occurs for the hydrogen release process of liquid organic hydrogen carriers (LOHCs), the regenerative cooling of advanced aircraft, etc. But the synergistic effects of Pt active sites are still ambiguous. Herein, a series of Pt-based catalysts with tunable Pt0-Ptδ+ sites were fabricated by changing the ratio of highly dispersed defected TiO2 on MCM-41 (M41) for efficient dehydrogenation of methylcyclohexane (MCH). The characterizations indicate TiO2 nanoparticles (NPs) are highly dispersed on M41 support, and possess abundant Ti3+/oxygen vacancies. The increase of TiO2 loading amount can enhance the interaction between Pt NPs and TiO2, which increases Ptδ+/Pt0 ratio gradually. The dehydrogenation test and theoretical results confirm that the synergistic effect of Pt0 and Ptδ+ sites contributes the optimal dehydrogenation performance, in which Pt0 promotes the consecutive C–H bond cleavage and Ptδ+ significantly decreases the desorption energy barrier for H2 and toluene (TOL). Specifically, the MCH conversion (when applied for LOHCs) is ca. 88 % and the selectivity of TOL is over 99.5 % under 1.0Pt/0.5TiO2/M41, while the high MCH conversion of 90 % and TOL selectivity of more than 86 % are achieved under 1.0Pt/1.0TiO2/M41 (as regenerative cooling for hypersonic vehicle). This work provides the approach of modulating the synergistic active sites to obtain high-performance dehydrogenation catalyst.

Constructing the synergistic active sites of nickel bicarbonate supported Pt hierarchical nanostructure for efficient hydrogen evolution reaction

Constructing synergistic active sites and optimizing the cooperative adsorption energies for hydrogen and hydroxyl based intermediates are two essential strategies to improve the sluggish kinetics of hydrogen evolution reaction (HER) in alkaline medium. However, it is still in its infancy to simultaneously achieve these goals, especially for designing a well-defined carrier with multiple hydroxyl adsorption sites. Herein, the Ni(HCO3)2 nanoplates (NHC) with horizontal interfaces sites of Ni-terminated NiO, NiOOH, NiCOO, and Ni(OH)2 were employed as the hydroxyl adsorption active sites, which could anchor Pt particles with hydrogen adsorption active sites, constructing the synergistic active sites (NHC-Pt) for HER catalysis. Evidenced by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS), the NHC could affect the chemical state and electronic structure of Pt particles by forming bond of Pt-O which could reduce the reaction energy barriers, facilitate the adsorption of hydrogen and establishment of H–H bond. Furthermore, density functional theory (DFT) theoretical calculation revealed that the related process of hydroxide was the rate-determining step. It is demonstrated the hydroxyl group presents the lowest energy barrier for desorption in the process of HER when the gradual desorption process could be described as a migration from Ni(HCO3)2·OH directly or via other Ni-based systems formed after partial decomposition of nickel hydrocarbonate to Ni(OH)2···OH with following desorption. As a result, the NHC-Pt hierarchical nanostructure demonstrated superior activity towards HER in a pH-universal solution. This enhancement can be attributed to the optimized electronic structure of Pt, the migration of hydroxyl group on NHC substrates, and the synergistic effects between the NHC carrier and Pt particles.

Comparative study of photocatalytic H2 production by nickel chalcogenides1+x based Zn3In2S6 photocatalytic system

Exploiting metal chalcogenide-based photocatalysts has fascinated researchers as a source of green hydrogen (H2) energy. Herein, we have designed a novel selenium-enriched NiSe1+x/ZIS (NiSexZ) photocatalytic system via a two-step hydrothermal and facile photo-deposition method. It was fascinating to conclude here that the NiSexZ photocatalytic system showed boosted H2 evolution results in comparison with other sulphur-enriched NiS1+x/ZIS (NiSxZ) and tellurium-enriched NiTe1+x/ZIS (NiTexZ). The optimized NiSe0.5Z composite exhibited a photocatalytic H2 evolution of 3.24 mmol g-1 h-1, a 9.8-fold increase over pure ZIS and it demonstrated an apparent quantum efficiency (AQE) of 2.06 % via 420 nm filter. Moreover, sulphur (S), selenium (Se), and tellurium (Te) synergistic active sites were exposed to promote H2 evolution reaction in this work. Given the significant advancements and commendable performance exhibited by the Se-Hads across the week bond, it is extremely probable that the NiSe1+x cocatalyst holds immense potential for the development of sophisticated photocatalytic materials.

Ferrocene-based metal-organic frameworks with dual synergistic active sites for selectively electrochemical removal of arsenic from contaminated water

The effective removal of trace levels of the highly toxic arsenite (As(Ⅲ)) from groundwater is crucial to address the threat to drinking water supply. Herein, we developed an electrochemical separation system utilizing redox-active ferrocene-based metal-organic frameworks (termed Fe-DFc) for selective removal of As(III). This system leveraged 1,1′-ferrocenedicarboxylic acid as a ligand coordinated with iron, enabling the highly selective capture and conversion of As(III) from groundwater. The Fe-DFc electrode-based electrochemical system not only effectively removed As(III) even in the presence of a 1250-fold excess of competing electrolytes, but also converted about 96 % of the adsorbed As(III) into the less toxic As(V), surpassing the results of those documented in the current literature. X-ray absorption fine structure analysis and density functional theory calculations demonstrated that the high selectivity of Fe-O6 moiety and the exceptional redox activity of Fc synergistically contributed to the efficient removal of As(III). Moreover, the electrochemical separation system enabled the remediation of arsenic-contaminated groundwater at a low energy cost of 0.033 kWh m−3 during long-term operation, highlighting the application potential of the electrochemical technology for arsenic removal from contaminated water.

Tandem Fields Facilitating Directional Carrier Migration in Van der Waals Heterojunction for Efficient Overall Piezo-Synthesis of H2O2.

Piezo-synthesis of H2O2 utilizing sustainable mechanical energy as well as earth-abundant water and oxygen is a green, cost-effective, and promising approach. However, achieving simultaneous two-electron water oxidation reaction (2e- WOR) and two-electron oxygen reduction reaction (2e- ORR) faces huge challenges due to insufficient synergistic active sites and slow/messy carrier transfer. Herein, a novel 2D/2D van der Waals heterojunction consisting of BiOIO3 and carbon nitride (BIO/CN) is elaborately designed for highly efficient overall H2O2 piezo-synthesis. Theoretical/experimental results reveal that a Z-scheme electron transfer is formed and facilitated by the tandem interfacial electric field and the bulk piezo-polarization field. On this basis, the carriers are efficiently separated while the oxidation/reduction capacity is preserved, thus providing the strong driving force for the 2e- WOR and 2e- ORR on BIO and CN, respectively. Furthermore, the kinetic and thermodynamic processes of WOR and ORR for H2O2 synthesis improve remarkably. Therefore, BIO/CN exhibits an excellent H2O2 yield of 259.8µM within 30min in pure water and air atmosphere (without any sacrificial agents and aeration). This study provides a new idea on strategically controlling electron transfer toward high-efficiency H2O2 piezo-synthesis and expands the avenue for developing effective environmental purification materials.

Construction of Pt Single-Atom and Cluster/FeOOH Synergistic Active Sites for Efficient Electrocatalytic Hydrogen Evolution Reaction

Construction of Pt Single-Atom and Cluster/FeOOH Synergistic Active Sites for Efficient Electrocatalytic Hydrogen Evolution Reaction

Nitrogen Doping-Roused Synergistic Active Sites in Perovskite Enabling Highly Selective CO2 Photoreduction into CH4.

The intricate protonation process in carbon dioxide reduction usually makes the product unpredictable. Thus, it is significant to control the reactive intermediates to manipulate the reaction steps. Here, we propose that the synergistic La-Ti active sites in the N-La2Ti2O7 nanosheets enable the highly selective carbon dioxide photoreduction into methane. In the photoreduction of CO2 over N-La2Ti2O7 nanosheets, in situ Fourier transform infrared spectra are utilized to monitor the *CH3O intermediate, pivotal for methane production, whereas such monitoring is not conducted for La2Ti2O7 nanosheets. Also, theoretical calculations testify to the increased charge densities on the Ti and La atoms and the regulated formation energy barrier of *CO and *CH3O intermediates by the constructed synergistic active sites. Accordingly, the methane formation rate of 7.97 μL h-1 exhibited by the N-La2Ti2O7 nanosheets, along with an electron selectivity of 96.6%, exceeds that of most previously reported catalysts under similar conditions.

F Doping-Induced Multicomponent Synergistic Active Site Construction toward High-Efficiency Bifunctional Oxygen Electrocatalysis for Rechargeable Zn-Air Batteries.

The commercialization of rechargeable Zn-air batteries (ZABs) relies on the material innovation to accelerate the sluggish oxygen electrocatalysis kinetics. Due to the differentiated mechanisms of reverse processes, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), rationally integrating dual sites for bifunctional oxygen electrocatalysis is prerequisite yet remains challenging. Herein, multicomponent synergistic active sites within highly graphitic carbon substrate are exquisitely constructed, which is accomplished by fluorine (F) modulation strategy. The incorporation of F dopants facilitates pyridinic N formation for anchoring single metal sites, thus guaranteeing the coexistence of sufficient M-Nx sites and metal nanoparticles toward bifunctional oxygen electrocatalysis. As a result, the optimal catalyst, denoted as F NH2-FeNi-800, outperforms commercial Pt/C+RuO2 with smaller gap between Ej = 10 and E1/2 (ΔE) of 0.63V (vs 0.7V for Pt/C+RuO2), demonstrating its superior bifunctionality. Beyond that, its superiority is validated in homemade rechargeable ZABs. ZABs assembled using F NH2-FeNi-800 as the air cathode delivers higher peak power density (123.8mW cm-2) and long-cycle lifetime (over 660 cycles) in comparison with Pt/C@RuO2 (68.8mW cm-2; 300 cycles). The finding not only affords a highly promising oxygen electrocatalyst, but also opens an avenue to constructing multifunctional active sites for heterogeneous catalysts.

Cu–Fe Synergistic Active Sites Boost Kinetics of Electrochemical Nitrate Reduction

AbstractElectrochemical conversion of nitrate offers an efficient solution to nitrate pollution and a sustainable strategy for ammonia generation. Cu and Fe bimetallic electrocatalysts exhibit excellent electrochemical reduction of nitrate (NO3RR) reactivity but the conventional preparation strategy is complex and time‐consuming and this reaction is still suffers from unsatisfied kinetic and unidentified mechanisms. Herein, in situ electrodeposition strategy is employed to induce Cu to modify the Fe active sites of iron‐based N‐doping carbon nanofiber electrode (Fe/Fe3C@NCNFs) during NO3RR in Cu‐contained nitrate solution. Benefiting from the synergistic effect between Cu and Fe sites of Cu─Fe/Fe3C@NCNFs electrode, superior activity of rate‐determining reaction (*NO3 to *NO2) and reduced energy barriers of the following deoxidation and hydrogenation steps are achieved. Compared with Fe/Fe3C@NCNFs‐500, the pseudo‐first‐order (PFO) rate constant for NO3RR by Cu─Fe/Fe3C@NCNFs demonstrates nearly two‐fold improvement with high current efficiencies over wide pH and voltage range. Furthermore, the maximum NO3─N removal capacity and N2 selectivity of Cu─Fe/Fe3C@NCNFs reach 15593.8 mg N g−1 Fe and ca. 92% after twenty cycles. This work offers an avenue for highly active bimetallic electrode design, paving more insights into the interactions between active site construction and NO3RR performance.

High density iridium synergistic sites boosting CO-tolerate performance for PEMFC anode

The usage of cheap crude H2 in proton-exchange membrane fuel cells (PEMFCs) is still unrealistic to date, due to the suffering of the current Pt based nano-catalysts from impurities such as CO in anode. Recently, synergistic active sites between single atom (SA) and nanoparticle (NP) have been found to be promising for overcoming the poisoning problem. However, lengthening the nanoparticle-single atom (SA–NP) interface, i.e., constructing high density synergistic active sites, remains highly challenging. Herein, we present a new strategy based on molecular fusion strategy to create abundant SA–NP interfaces, with high density SA–NP interfaces created on a two dimensional nitrogen doped carbon nanosheets (Ir-SACs&NPs/NC). Owing to the abundance of SA–NP interface sites, the catalyst was empowered with a high tolerance towards up to 1000 ​ppm CO in H2 feed. These findings provide guidelines for the design and construction of active and anti-poisoning catalysts for PEMFC anode.

Constructing self-standing Fe2O3-Pt/NF nanoflowers with synergistic active sites for efficient electrocatalytic overall (sea) water splitting

Designing cost-effective and high-stable heterostructures with synergistic active sites could simultaneously catalyze oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) for the (sea) water splitting. However, there are still...

Construction of synergistic active sites on MoS2 basal plane by interfacing with C60 derivative for enhanced photocatalytic hydrogen evolution coupled with biomass alcohol conversion

As a promising alternative to platinum, molybdenum disulfide (MoS2) is widely utilized as catalyst/co-catalyst in hydrogen evolution reaction (HER). However, its inactive basal plane greatly hampers its catalytic activity. Herein, we propose a function-oriented strategy to enhance the catalytic activity of MoS2 by interfacing with fullerene derivatives, specifically indene-C60 bisadduct (ICBA). The ICBA-MoS2 hybrid was then employed as an efficient co-catalyst, in conjunction with CdS, to construct a photocatalyst for solar-driven hydrogen production coupled with the selective oxidation of furfural alcohol (FOL) to furfural (FAL). The optimized 5 % ICBA-MoS2/CdS (5 %-IMC) sample exhibits a remarkable H2 and FAL production rates of 978 and 1160 μmol h−1 g−1, respectively, which was 2.4 times higher than that of the primitive sample without ICBA modified. This prominent catalytic performance can be attributed to the high activity of synergistic active sites in ICBA-MoS2, as well as the speed transportation and separation of the photogenerated charges from CdS to ICBA-MoS2, as evidenced by both experimental and theoretical investigations.

Synergistic effect between Ni single atoms and Ni nanoparticles for effectively boosting sustainable co-electrolysis of CO2 and hydrazine

The intrinsic performance of single atom catalysts (SACs) to electrochemical CO2 reduction reaction (ECRR) is limited due to the absence of synergistic active sites. Herein, Ni single atom (NiSAs) and Ni nanoparticles (NiNPs) are co-loaded on nitrogen-doped hollow carbon spheres (N-HCSs) by a one-step calcination method, which exhibits high CO selectivity in H-type cell with aqueous solution or an ionic liquid as electrolyte. Particularly, NiSAs-NPs-N-HCSs demonstrate a CO selectivity of 98.98%, yielding an industrial level CO current density of 152.7 mA cm−2 in flow cell. In situ Raman spectroscopy and in situ infrared characterization technology confirm that *COOH and *CO are important intermediates in the ECRR process. Theoretical computations suggest that coexisting NiNPs can reduce the energy barrier of *COOH, thereby improving the ECRR performance, indicating the synergistic effect between NiSAs and NiNPs in the ECRR process. Moreover, NiSAs-NPs-N-HCSs is applied to the membrane electrode assembly system coupling the hydrazine oxidation reaction (HzOR), which can significantly reduce the voltage about 836 mV at 100 mA cm−2.

Sulfur-nitrogen synergistic active sites enable continuous and fast removal of organic pollutants in practical water matrix

The rational design of active sites in nanocarbons are the long-term pursuit for their practical applications. However, N, as the most potential active site, still encounters the problems of low atom utilization efficiency and stability in practical environmental remediation. Herein, we successfully constructed synergistic active sites consisting of graphitic N, pyridinic N, and thiophene S in heavy S, N co-doped hollow graphene spheres (HSNGS). The HSNGS exhibited exceptional efficiency in degrading tetracycline in real water, with a turnover frequency of 6.24 min−1, which is among the highest reported. Moreover, tetracycline dissolved in practical water could be continuously and rapidly eliminated by passing through a column filled with HSNGS, maintaining its high performance even after 40 consecutive cycles. In the synergistic active sites, graphitic N and pyridinic N species accepted electrons from peroxymonosulfate, generating singlet oxygen for tetracycline degradation. Simultaneously, thiophene S coordinated with metal ions present in the practical water, synergistically enhancing the degradation of tetracycline. Additionally, the coordinated metal ions provided protection for the synergistic active sites during peroxymonosulfate activation, preventing their oxidation and enabling the continuous and rapid degradation of tetracycline. This work opens up possibilities for the industrial application of nanocarbon materials in environmental remediation.

Direct OC-CHO coupling towards highly C2+ products selective electroreduction over stable Cu0/Cu2+ interface

Electroreduction of CO2 to valuable multicarbon (C2+) products is a highly attractive way to utilize and divert emitted CO2. However, a major fraction of C2+ selectivity is confined to less than 90% by the difficulty of coupling C-C bonds efficiently. Herein, we identify the stable Cu0/Cu2+ interfaces derived from copper phosphate-based (CuPO) electrocatalysts, which can facilitate C2+ production with a low-energy pathway of OC-CHO coupling verified by in situ spectra studies and theoretical calculations. The CuPO precatalyst shows a high Faradaic efficiency (FE) of 69.7% towards C2H4 in an H-cell, and exhibits a significant FEC2+ of 90.9% under industrially relevant current density (j = −350 mA cm−2) in a flow cell configuration. The stable Cu0/Cu2+ interface breaks new ground for the structural design of electrocatalysts and the construction of synergistic active sites to improve the activity and selectivity of valuable C2+ products.

Mesoporous Ru(Co, Ni)B bimetallic amorphous alloy for CO2 hydrogenation to formic acid

Amorphous metal alloy catalysts have attracted even-increasing attention owing to their high activity and selectivity. However, they are mainly prepared in ultrafine nanoparticles, which are easily gathered and challenging to separate. In this work, mesoporous Ru(Co, Ni)B bimetallic amorphous alloy catalysts with magnetic properties that can be easily recovered were synthesized via surfactant self-assembly. The as-prepared Ru1%CoB catalyst exhibited 578 μmol/g/h production rate and 99% selectivity to HCOOH during liquid phase CO2 hydrogenation owing to the unique amorphous alloy structure corresponding to the well-distributed, coordination-unsaturated, electron-enriched and synergistic active sites, which promoted the adsorption, activation, dissociation, and surface reaction of CO2 and H2. Moreover, the mesoporous channels also promoted the diffusion and adsorption of CO2 and H2. Besides, the Ru1%CoB catalyst also displayed good durability in CO2 hydrogenation owing to the robust stability against the crystallization of amorphous alloy, the collapse of mesopores, and the leaching of active sites.

Synergistic N-Doping and Heterointerface Engineering in W2C/W Nanoarrays Enable pH-Universal Hydrogen Evolution Catalysis

The electrocatalytic hydrogen evolution reaction (HER) by nonprecious metal-based cathodes provides a cost-effective way to store renewable energy as hydrogen fuel. However, pH variation on the cathode surface during electrolysis may lead to performance deterioration. Herein, the heterostructure electrode composed of nitrogen-doped ditungsten carbide/monolithic tungsten interface (N–W2C/W) is developed. The as-obtained electrode showed superior HER performance in pH-universal conditions, achieving −10 mA cm–2 with small overpotentials of 90, 90, and 82 mV in acidic, neutral, and alkaline electrolytes, respectively. Moreover, the electrocatalyst shows negligible performance decay after 24 h at the current densities of even −500 mA cm–2. Theoretical studies reveal that the interface W site exhibits suitable Gibbs free energy of hydrogen adsorption. Moreover, the unique interfacial structure provides synergistic active sites for water dissociation. This work provides an approach to design an interfacial structure based on nonprecious metals for highly efficient HER electrocatalysis.

Hierarchical multiphase (Ni, Co)-Se with adjustable interlayer distance derived from reconstructed ZIF-L for enhanced hybrid-supercapacitors

As attractive electrodes for hybrid-supercapacitors (HSCs), transition-metal selenides (TMSes) demonstrate ideal conductivity and abundant valence states for rapid charge. However, the traditional TMSes are restricted to accumulative or low-correlation active sites and the single phase. Herein, reasonable structures rich in synergistic active sites are solutions to manufacture high-efficiency electrodes. Regular hexagonal NiCo-LDH (layered double hydroxide) is reconstructed on hollow carbon–nitrogen frameworks (CNFs) and a stable hierarchical system is constructed. After systematic gradient selenization (time/temperature), the controllable interlayer spacing with phase transformation of LDH derivatives (multiphase selenides: M-(Ni, Co)-Se (Co9Se8, NiSe2)) is researched. It is found that the hydroxyl adsorption and conductivity can be enhanced due to the synergistic effect between the multiphase TMSes, which can significantly improve the capacity of the electrode. The optimal electrode M-(Ni, Co)-Se@CNFs/CC (carbon cloth) (378.9 mAh g−1, 1 A−1, 6 M KOH) is obtained after systematic research. Furthermore, the HSC (M-(Ni, Co)-Se@CNFs/CC//Activated carbon) exhibits ultrahigh energy density (96.6 Wh kg−1) and excellent stability (10,000 cycles, 133.6 %, 6 M KOH), which is superior to most similar work. The novel path of multiphase synergy is successfully realized through the multiphase system, which has reference significance in the high-efficiency HSC industry.