Effects of cobalt carbide on Fischer–Tropsch synthesis with MnO supported Co-based catalysts

Cobalt carbide(Co2C)was considered as potential catalysts available for large-scale industrialization of transforming syngas(H2 and CO)to clean fuels.Herein,we successfully synthesized Co-based catalysts with MnO supported,to comprehend the effects of Co2C for Fischer–Tropsch synthesis(FTS)under ambient conditions.The huge variety of product selectivity which was contained by different active sites(Co and Co2C)has been found.Furthermore,density functional theory(DFT)shows that Co2C is efficacious of CO adsorption,whereas is weaker for H adsorption than Co.Combining the advantages of Co and Co2C,the catalyst herein can not only obtain more C5+products but also suppress methane selectivity.It can be a commendable guide for the design of industrial application products in FTS.

Role of local coordination in bimetallic sites for oxygen reduction: A theoretical analysis

Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic(Fe and Co)carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways.The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe.The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen.Interestingly,the preadsorption of*OH resulted in the apparent change of metal atoms'electronic states with the d-band center shifting toward the Fermi level,thereby boosting reaction activity.The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.

Understanding the synergetic interaction within α-MoC/β-Mo2C heterostructured electrocatalyst

Constructing heterostructure is an important strategy to design efficient electrocatalysts. The synergetic interaction between dissimilar materials has been considered as the origin of the activity enhancement,however, the interfacial interaction is challenging to probe, thus, the underlying mechanism remains obscure. Here, we reported a heterostructured α-MoC/β-Mo2 C electrocatalyst for hydrogen evolution in alkaline media, which shows a significant electrocatalytic activity improvement as compared to the single component. Based on extensive characterizations including high-resolution transmission electron microscopy and X-ray absorption fine structure(XAFS) spectroscopy, together with density functional theory, we unraveled the synergetic interaction between α-MoC and β-Mo2 C, implying that α-Mo C sites are beneficial for water dissociation and hydrogen prefers to release on β-Mo2 C sites.

Characterization of CoMn catalyst by in situ X-ray absorption spectroscopy and wavelet analysis for Fischer–Tropsch to olefins reaction

Cobalt carbide has recently been reported to catalyse the FTO con version of syngas with high selectivity for the production of lower olefins (C2-C4). Clarifying the formation process and atomic structure of cobalt carbide will help understand the catalytic mechanism of FTO. Herein, hydrogenati on of carb on monoxide was investigated for cobalt carbide synthesized from CoMn catalyst, followed by X-ray diffraction, transmission electron microscopy, temperature programmed reaction and in situ X-ray absorption spectroscopy. By monitoring the evolution of cobalt carbide during syngas conversion, the wavelet transform results give evidenee for the formation of the cobalt carbide and clearly demonstrate that the active site of catalysis was cobalt carbide.

Unveiling the mechanism of charge compensation in Li_(2)Ru_(x)Mn_(1-x)O_(3)by tracking atomic structural evolution

The relationship between the structural evolution and redox of Li-rich transition-metal layered oxides(LLOs)cathodes remains ambiguous,obstructing the development of high-performance lithium-ion(Li^(+))battery.Herein,the coherent effects of local atomic and electronic structure in Li_(2)Ru_(x)Mn_(1-x)O_(3)(LRMO)with a wide voltage window(1.3–4.8 V)is identified by in situ X-ray absorption fine spectroscopy(XAFS)and chemometrics.We not only skillfully separated the redox active structures to track the electrochemical path,but also visualized the coupling mechanism between the evolution of Ru-Ru dimer and the(de)excitation of cations and anions.Furthermore,introducing manganese triggers the“heterogeneity”of coordination environment and electronic structure between Ru and Mn after discharge to 3 V.The change of thermodynamic and kinetic paths affects the relithiation,and further leads to the hysteresis of the anion activation structure relaxation of Li_(2)Ru_(0.4)Mn_(0.6)O_(3)relative to Li_(2)RuO_(3)(LRO).Additionally,it is demonstrated that the high charge cut-off voltage restrains the relaxation of anionic active structure in LRO from a new perspective through comparative experiments.Our work associates the evolution of atomic structure with charge compensation and negative electrochemical reactions such as voltage hysteresis(VH)and capacity attenuation,deepening the understanding electrochemical reaction mechanism of LLOs during the first cycle and providing a theoretical support for the further design and synthesis of high-efficiency cathodes.

Erratum to: Bimetallic clusters confined inside silicalite-1 for stable propane dehydrogenation

Erratum to Nano Research,2023,16(8):10881–10889 https://doi.org/10.1007/s12274-023-5953-y The equal contribution symbols were unfortunately missing.Instead of Xueer Wei1,Jiawei Cheng1,Yubing Li1,Kang Cheng1,2(✉),Fanfei Sun3,4(✉),Qinghong Zhang1(✉),and Ye Wang1,21 State Key Laboratory of Physical Chemistry of Solid Surfaces,Collaborative Innovation Center of Chemistry for Energy Materials,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China 2 Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM),Xiamen 361005,China 3 Shanghai Synchrotron Radiation Facility,Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201800,China 4 Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201204,China.

Bimetallic clusters confined inside silicalite-1 for stable propane dehydrogenation

The noble metal-based bimetallic clusters with high atom utilization and surface energy have been widely applied in heterogeneous catalysis,but the stabilization of these metastable clusters in harsh reaction conditions is quite challenging.Herein,we synthesize a series of Pt-,Pd-,and Ru-based clusters promoted by a second non-noble metal(Zn,Cu,Sn,and Fe),which are confined inside silicalite-1(pure silica,S-1)crystals by a ligand-protected method.The second metal could well stabilize and disperse the noble atoms inside the rigid S-1 zeolites via Si–O–M bonds,thus enabling to lower the usage of expensive noble metals in catalysts.The as-synthesized bimetallic catalysts exhibited excellent performance in non-oxidative propane dehydrogenation(PDH)reaction,which is typically operated above 500℃.The PtZn@S-1,PtCu@S-1,and PtSn@S-1 with only a~0.17 wt.%Pt loading offer a significant enhancement in PDH performance compared with the conventional PtSn/Al_(2)O_(3)catalyst with a 0.5 wt.%Pt loading prepared by impregnation method.Notably,the PtSn@S-1 provides a propane conversion of 45%with a 99%propylene selectivity at 550℃,close to the thermodynamic equilibrium.Furthermore,the PtSn@S-1 exhibits excellent stability during 300 h on stream and high tolerance to regeneration by a simple calcination step.

Boosting hydrogen peroxide production via establishment and reconstruction of single-metal sites in covalent organic frameworks

Covalent organic frameworks(COFs)have been well developed in electrocatalytic systems owing to their controllable skeletons,porosities,and functions.However,the catalytic process in COFs remains underexplored,hindering an in-depth understanding of the catalytic mechanism.In this work,uniform Pt-N_(1)O_(1)Cl_(4)sites chelated via C-N and C=O bonds along the one-dimensional and open channels of TP-TTA-COF were established.Different from conventional single-metal sites constructed for the near-free platinum for hydrogen evolution,the as-constructed PtCl-COF showed 2e−oxygen reduction for H_(2)O_(2)production.We tracked the dynamic evolution process of atomic Pt sites in which Pt-N_(1)O_(1)Cl_(4)was transformed into Pt-N_(1)O_(1)(OH)_(2)using in situ X-ray adsorption.The theoretical calculations revealed that the strong Pt-support interaction in Pt-N_(1)O_(1)(OH)_(2)facilitated*OOH formation and thus led to higher selectivity and activity for the oxygen reduction reaction in the 2e−pathway.This work can expand the applications of COFs through the regulation of their local electronic states for the manipulation of the metal center.

Evolution of Zn(Ⅱ) single atom catalyst sites during the pyrolysis-induced transformation of ZIF-8 to N-doped carbons

The pyrolysis of zeolitic imidazolate frameworks(ZIFs) is becoming a popular approach for the synthesis of catalysts comprising porphyrin-like metal single atom catalysts(SACs) on N-doped carbons(M-N-C).Understanding the structural evolution of M-N-C as a function of ZIF pyrolysis temperature is important for realizing high performance catalysts.Herein,we report a detailed investigation of the evolution of Zn single atom catalyst sites during the pyrolysis of ZIF-8 at temperatures ranging from 500 to 900℃.Results from Zn L-edge and Zn K-edge X-ray absorption spectroscopy studies reveal that tetrahedral ZnN4 centers in ZIF-8 transform to porphyrin-like ZnN4 centers supported on N-doped carbon at temperatures as low as 600℃.As the pyrolysis temperature increased in the range 600-900℃,the Zn atoms moved closer to the N4 coordination plane.This subtle geometry change in the ZnN4 sites alters the electron density on the Zn atoms(formally Zn2+),strongly impacting the catalytic performance for the peroxidase-like decomposition of H2 O2.The catalyst obtained at 800℃(Zn-N-C-800) offered the best performance for H2 O2 decomposition.This work provides valuable new insights about the evolution of porphyrin-like single metal sites on N-doped carbons from ZIF precursors and the factors influencing SAC activity.

Microwave-assisted synthesis of photoluminescent glutathione-capped Au/Ag nanoclusters： A unique sensor-on-a-nanoparticle for metal ions, anions, and small molecules

Even though great advances have been achieved in the synthesis of luminescent metal nanoclusters, it is still challenging to develop metal nanoclusters with high quantum efficiency as well as multiple sensing functionalities. Here, we demonstrate the rapid preparation of glutathione-capped Au/Ag nanoclusters （GS-Au/Ag NCs） using microwave irradiation and their unique sensing capacities. Compared to bare GS-Au NCs, the doped Au/Ag NCs possess an enhanced quantum yield （7.8% compared to 2.2% for GS-Au NCs）. Several characterization techniques were used to elucidate the atomic composition, particulate character, and electronic structure of the fabricated NCs. According to the X-ray photoelectron spectroscopy （XPS） and X-ray absorption near-edge structure （XANES） spectra, a significant amount of Au exists in the oxidized state as Au（I）, and the Ag atoms are positively charged. In contrast to those nanoclusters that detect only one analyte, the GS-Au/Ag NCs can be used as a versatile sensor for metal ions, anions, and small molecules. In this manner, the NCs can be regarded as a unique sensor-on-a-nanoparticle.

Unraveling the Dynamic Structural Evolution of Phthalocyanine Catalysts during CO_(2) Electroreduction

Understanding the atomic and electronic changes of active sites promotes the whole new sight into electrochemical carbon dioxide reduction reaction(CO_(2)RR),which provides a feasible strategy to achieve carbon neutrality.Here we employ operando high-energy resolution fluorescence-detected Xray absorption spectroscopy(HERFD-XAS)to track the structural evolution of Ni(II)phthalocyanine(NiPc),considered as the model catalysts with uniform Ni-N_(4)-C_(8) moiety,during the CO_(2)RR.The HERFD-XAS method is in favor of elucidating the interaction of the reactant/catalyst interface from the atomic electronic structure dimension,facilitating the establishment of the catalytic mechanism and the dynamic structure changes.Based on operando measurement,surface sensitive difference spectra(△μ)and spectroscopy simulation,the interfacial interactions between the active sites of NiPc and reactants are monitored and the Ni species gradually reduced by increasing the applied potential is discovered.HERFD-XAS method offers an advanced and powerful tool for elucidating the complex catalytic mechanism in further various systems.

Self-supported Ni6MnO8 3D mesoporous nanosheet arrays with ultrahigh lithium storage properties and conversion mechanism by in-situ XAFS

Murdochite-type Ni6MnO8 three-dimensional mesoporous nanosheet arrays grown on carbon cloth （NMO-SA/CC） are synthesized using an in-situ growth strategy. As self-supported binder-free anodes for LIBs, the NMO-SA/CC hierarchical nanostructures exhibit ultrahigh capacity, excellent cycling stability, and good rate capability. The excellent lithium storage performance can be ascribed to the perfect electrical contact between NMO-SA and CC. The mesopores in the thin nanosheet can maximize the electrode contact with the electrolyte by decreasing the Li＋ diffusion path. Moreover, these effects relieve the pulverization and agglomeration that originate from the large volume variations during the Li＋ intercalation/deintercalation cycles. The in-situ X-ray absorption fine structure （XAFS） spectrum recorded during the initial lithiation/delithiation processes reveals the conversion reaction process.