Atomic Dispersed Hetero‑Pairs for Enhanced Electrocatalytic CO_(2)Reduction

Electrochemical carbon dioxide reduction reaction(CO_(2)RR)involves a variety of intermediates with highly correlated reaction and ad-desorption energies,hindering optimization of the catalytic activity.For example,increasing the binding of the*COOH to the active site will generally increase the*CO desorption energy.Breaking this relationship may be expected to dramatically improve the intrinsic activity of CO_(2)RR,but remains an unsolved challenge.Herein,we addressed this conundrum by constructing a unique atomic dispersed hetero-pair consisting of Mo-Fe di-atoms anchored on N-doped carbon carrier.This system shows an unprecedented CO_(2)RR intrinsic activity with TOF of 3336 h−1,high selectivity toward CO production,Faradaic efficiency of 95.96%at−0.60 V and excellent stability.Theoretical calculations show that the Mo-Fe diatomic sites increased the*COOH intermediate adsorption energy by bridging adsorption of*COOH intermediates.At the same time,d-d orbital coupling in the Mo-Fe di-atom results in electron delocalization and facilitates desorption of*CO intermediates.Thus,the undesirable correlation between these steps is broken.This work provides a promising approach,specifically the use of di-atoms,for breaking unfavorable relationships based on understanding of the catalytic mechanisms at the atomic scale.

Cooperation between single atom catalyst and support to promote nitrogen electroreduction to ammonia:A theoretical insight

The co-catalysis between single atom catalyst(SAC)and its support has recently emerged as a promising strategy to synergistically boost the catalytic activity of some complex electrochemical reactions,encompassing multiple intermediates and pathways.Herein,we utilized defective BC_(3)monolayer-supported SACs as a prototype to investigate the cooperative effects of SACs and their support on the catalytic performance of the nitrogen reduction reaction(NRR)for ammonia(NH_(3))production.The results showed that these SACs can be firmly stabilized on these defective BC_(3)supports with high stability against aggregation.Furthermore,co-activation of the inert N_(2)reactant was observed in certain embedded SACs and their neighboring B atoms on certain BC3 sheets due to the noticeable charge transfer and significant N–N bond elongation.Our high-throughput screening revealed that the Mo/DV_(CC)and W/DV_(CC)exhibit superior NRR catalytic performance,characterized by a low limiting potential of−0.33 and−0.43 V,respectively,which can be further increased under acid conditions based on the constant potential method.Moreover,varying NRR catalytic activities can be attributed to the differences in the valence state of active sites.Remarkably,further microkinetic modeling analysis displayed that the turnover frequency of N_(2)–to–NH_(3)conversion on Mo/DV_(CC)is as large as 1.20×10^(−3)s^(−1)site^(−1) at 700 K and 100 bar,thus guaranteeing its ultra-fast reaction rate.Our results not only suggest promising advanced electrocatalysts for NRR but also offer an effective avenue to regulate the electrocatalytic performance via the co-catalytic metal–support interactions.

Mo_(2)P Monolayer as a Superior Electrocatalyst for Urea Synthesis from Nitrogen and Carbon Dioxide Fixation:A Computational Study

Urea synthesis through the simultaneous electrocatalytic reduction of N_(2)and CO_(2)molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production,in which the development of stable,highly efficient,and highly selective catalysts to boost the chemisorption,activation,and coupling of inert N_(2)and CO_(2)molecules remains rather challenging.Herein,by means of density functional theory computations,we proposed a new class of two-dimensional nanomaterials,namely,transition-metal phosphide monolayers(TM_(2)P,TM=Ti,Fe,Zr,Mo,and W),as the potential electrocatalysts for urea production.Our results showed that these TM_(2)P materials exhibit outstanding stability and excellent metallic properties.Interestingly,the Mo_(2)P monolayer was screened out as the best catalyst for urea synthesis due to its small kinetic energy barrier(0.35 eV)for C-N coupling,low limiting potential(-0.39 V),and significant suppressing effects on the competing side reactions.The outstanding catalytic activity of the Mo_(2)P monolayer can be ascribed to its optimal adsorption strength with the key^(*)NCON species due to its moderate positive charges on the Mo active sites.Our findings not only propose a novel catalyst with high-efficiency and high-selectivity for urea production but also further widen the potential applications of metal phosphides in electrocatalysis.

Ultrathin origami accordion-like structure of vacancy-rich graphitized carbon nitride for enhancing CO_(2) photoreduction

Retaining the ultrathin structure of two-dimensional materials is very important for stabilizing their catalytic performances.However,aggregation and restacking are unavoidable,to some extent,due to the van der Waals interlayer interaction of two-dimensional materials.Here,we address this challenge by preparing an origami accordion structure of ultrathin twodimensional graphitized carbon nitride(oa-C_(3)N_(4))with rich vacancies.This novel structured oa-C_(3)N_(4) shows exceptional photocatalytic activity for the CO_(2) reduction reaction,which is 8.1 times that of the pristine C_(3)N_(4).The unique structure not only prevents restacking but also increases light harvesting and the density of vacancy defects,which leads to modification of the electronic structure,regulation of the CO_(2) adsorption energy,and a decrease in the energy barrier of the carbon dioxide to carboxylic acid intermediate reaction.This study provides a new avenue for the development of stable highperformance two-dimensional catalytic materials.

Revealing the Intrinsic Peroxidase-Like Catalytic Mechanism of Heterogeneous Single-Atom Co-MoS2

The single-atom nanozyme is a new concept and has tremendous prospects to become a next-generation nanozyme.However,few studies have been carried out to elucidate the intrinsic mechanisms for both the single atoms and the supports in single-atom nanozymes.Herein,the heterogeneous single-atom Co-MoS2(SA Co-MoS2)is demonstrated to have excellent potential as a high-performance peroxidase mimic.Because of the well-defined structure of SA Co-MoS2,its peroxidase-like mechanism is extensively interpreted through experimental and theoretical studies.Due to the different adsorption energies of substrates on different parts of SA Co-MoS2 in the peroxidase-like reaction,SA Co favors electron transfer mechanisms,while MoS2 relies on Fenton-like reactions.The different catalytic pathways provide an intrinsic understanding of the remarkable performance of SA Co-MoS2.The present study not only develops a new kind of single-atom catalyst(SAC)as an elegant platform for understanding the enzyme-like activities of heterogeneous nanomaterials but also facilitates the novel application of SACs in biocatalysis.

N-heterocyclic carbene as a promising metal-free electrocatalyst with high efficiency for nitrogen reduction to ammonia

Electrocatalytic nitrogen reduction reaction(NRR)at ambient conditions holds great promise for sustainably synthesizing ammonia(NH3),while developing highly-efficient,long-term stable,and inexpensive catalysts to activate the inert N≡N bond is a key scientific issue.In this work,on the basis of the concept"N-heterocyclic carbenes(NHCs)",we propose a carbon decorated graphitic-carbon nitride(C/g-C3N4)as novel metal-free NRR electrocatalyst by means of density functional theory(DFT)computations.Our results reveal that the introduced C atom in g-C3N4 surface can be regarded as NHCs and catalytic sites for activating N≡N bond,and are stabilized by the g-C3N4 substrate due to sterically disfavored dimerization.Especially,this NHCs-based heterogeneous catalysis can efficiently reduce the activated N2 molecule to NH3 with a low overpotential of 0.05 V via an enzymatic mechanism.Our work is the first report of NHCs-based electrocatalyst for N2 fixation,thus opening an alternative avenue for advancing sustainable NH3 production.

The 9L^(LUC)/Wistar rat glioma model is not suitable for immunotherapy

The availability of a well-characterized animal brain tumor model will play an important role in identifying treatments for human brain tumors. Wistar rats bearing 9L glioma cells can develop solid, well-circumcised tumors, and may be a useful animal model for the evaluation of various therapeutic approaches for gliosarcomas. In this study, the 9L/Wistar rat glioma model was produced by intracerebral implantation of 9L^LUC glioma cells syngenic to Fischer 344 （F344） rats. Bioluminescence imaging showed that tumors progressively grew from day 7 to day 21 in 9L^LUC/F344 rats, and tumor regression was found in some 9L^LUC/Wistar rats. Hematoxylin-eosin staining verified that intracranial tumors were gliomas. Immunohistochemistry results demonstrated that no CD4- and CD8-positive cells were found in the syngeneic 9L^LUC/F344 model. However, many infiltrating CD4- and CD8-positive cells were observed within the tumors of the 9L^LUC/Wistar model. Our data suggests that compared with 9L/F344 rats, 9L glioma Wistar rats may not be suitable for evaluating brain glioma immunotherapies, even though the model induced an immune response and exhibited tumor regression.

Tuning precise numbers of supported nickel clusters on graphdiyne for efficient CO_(2)electroreduction toward various multi-carbon products

Compared to single-atom catalysts,supported metal clusters can exhibit enhanced activity and designated selectivity in heterogeneous catalysis due to their unique geometric and electronic features.Herein,by means of comprehensive density functional theory (DFT) computations,we systematically investigated the potential of several Ni clusters supported on graphdiyne (Ni_(x)/GDY,x=1–6) for CO_(2) reduction reaction (CO_(2)RR).Our results revealed that,due to the strong interaction between Ni atoms and sp-hybridized C atoms,these supported Ni clusters on GDY exhibit high stabilities and excellent electronic properties.In particular,according to the computed free energy profiles for CO_(2)RR on these Ni_(x)/GDY systems,the anchored Ni_(4) cluster was revealed to exhibit high CO_(2)RR catalytic activity with a small limiting potential and moderate kinetic barrier for C–C coupling,and CH_(4),C_(2)H_(5)OH,and C_(3)H_(7)OH were identified as the main products,which can be attributed to its strong capacity for CO_(2) activation due to its unique configuration and excellent electronic properties.Thus,by carefully controlling the precise numbers of atoms in sub-nano clusters,the spatially confined Ni clusters can perform as promising CO_(2)RR catalysts with high-efficiency and high-selectivity,which may provide a useful guidance to further develop novel and low-cost metal clusters-based catalysts for sustain CO_(2)conversion to valuable chemicals and fuels.

Achieving efficient N_(2)electrochemical reduction by stabilizing the N2H*intermediate with the frustrated Lewis pairs

Electrocatalytic nitrogen reduction reaction(eNRR)with sustainable energy under ambient conditions represents an attractive approach to producing ammonia,but the design of the-state-of-the-art electrocatalyst with high efficiency and selectivity still faces formidable challenges.In contrast to traditional eNRR catalyst design strategies focusing on N≡N triple bond activation,we herein theoretically proposed an alternative strategy to improve eNRR performance via stabilizing the N_(2)H^(*)intermediate using catalysts with the frustrated Lewis pairs(FLPs),i.e.,transition metal(TM)atoms and boron(B)atom co-doped 2D black phosphorus(TM-B@BP).Our density functional theory(DFT)results reveal that the TM atom donates electrons to the adsorbed N_(2)molecule,while B atom provides empty orbital to stabilize the adsorption of N_(2)H^(*)intermediate.This framework successfully identifies five promising candidates(i.e.,Ti-B@BP,V-B@BP,Cr-B@BP,Mn-B@BP and Fe-B@BP)with low theoretical limiting potentials(−0.60,−0.41,−0.45,−0.43 and−0.50 V,respectively)and high selectivity for eNRR.We believe that the intermediate stabilization strategy introduced in current work offers a new opportunity to achieve accelerated and cost-effective ammonia synthesis with electrocatalysis.

Ambient electrosynthesis of urea from carbon dioxide and nitrate over Mo_(2)C nanosheet

Electrocatalytic synthesis of urea through C-N bond formation,converting carbon dioxide(CO_(2))and ni-trate(NO_(3)^(-)),presents a promising,less energy-intensive alternative to industrial urea production process.In this communication,we report the application of Mo_(2)C nanosheets-decorated carbon sheets(Mo_(2)C/C)as a highly efficient electrocatalyst for facilitating C-N coupling in ambient urea electrosynthesis.In CO_(2)-saturated 0.2 mol/L Na_(2)SO_(4)solution containing 0.05 mol/L NO_(3)^(-),the Mo_(2)C/C catalyst achieves an impres-sive urea yield of 579.13μg h^(-1)mg^(-1)with high Faradaic efficiency of 44.80%at-0.5 V versus the reversible hydrogen electrode.Further theoretical calculations reveal that the multiple Mo active sites enhance the formation of^(∗)CO and^(∗)NH_(2)intermediates and facilitate their C-N coupling.This research propels the use of Mo_(2)C-based electrodes in electrocatalysis and accentuates the capabilities of binary metal-based catalysts in C-N coupling reactions.

Applying machine-learning screening of single transition metal atoms anchored on N-dopedγ-graphyne for carbon monoxide electroreduction toward C_(1)products

Carbon monoxide electroreduction(COER)has been a key part of tandem electrolysis of carbon dioxide(CO_(2)),in which searching for high catalytic performance COER electrocatalysts remains a great challenge.Herein,by means of density functional theory(DFT)computations,we explored the potential of a series of transition metal atoms anchored on N-dopedγ-graphyne(TM@N-GY,TM from Ti to Au)as the COER electrocatalysts.We found that the final product selectivity of these single-atom catalysts depended on the position of the metal atom in the periodic table,with metals in the front and middle of each periodic period exhibiting high selectivity for CH_(4),while metals in the back producing CH_(3)OH.Machine learning(ML)found that metal atomic number was intrinsic to the difference in COER performance of these single-atom catalysts(SACs).The free energy changes showed that Mn@N-GY and Ni@N-GY exhibited outstanding COER catalytic performance for producing CH_(4)and CH_(3)OH,respectively.Our results provide theoretical and experimental guidance for designing efficient COER catalysts to generate C_(1)products.

Single-atom rhodium anchored on S-doped black phosphorene as a promising bifunctional electrocatalyst for overall water splitting

Superior bifunctional electrocatalysts with ultra-high stability and excellent efficiency are crucial to boost the oxygen evolution reaction(OER) and the hydrogen evolution reduction(HER) in the overall water splitting(OWS) for the sustainable production of clean fuels. Herein, comprehensive density functional theory(DFT) computations were performed to explore the potential of several single transition metal(TM) atoms anchored on various S-doped black phosphorenes(TM/Snx-BP) for bifunctional OWS electrocatalysis. The results revealed that these candidates display good stability, excellent electrical conductivity, and diverse spin moments. Furthermore, the Rh/S12-BP catalyst was identified as an eligible bifunctional catalyst for OWS process due to the low overpotentials for OER(0.43 V) and HER(0.02 V), in which Rh and its adjacent P atoms were identified as the active sites. Based on the computed Gibbs free energies of OH~*, O~*, OOH~* and H~*, the corresponding volcano plots for OER and HER were established.Interestingly, the spin moments and the charge distribution of the active sites determine the catalytic trends of OER and HER. Our findings not only propose a promising bifunctional catalyst for OWS, but also widen the potential application of BP in electrocatalysis.

Revisiting catalytic performance of supported metal dimers for oxygen reduction reaction via magnetic coupling from first principles

In this study,we selected 10 Co-based double-atom catalysts(DACs)catalysts,namely CoMN_(6)-gra(OH)(M?Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn),and investigated their oxygen reduction reactions(ORR)catalytic performances with/without considering the magnetic coupling by means of density functional theory(DFT)calculations.It was found that CoNiN_(6)-gra(OH),CoCuN_(6)-gra(OH),and CoZnN_(6)-gra(OH)exhibit good catalytic activity of ORR(with low overpotentials of 0.33,0.34 and 0.23 V,respectively)when the magnetic coupling is considered.In particular,magnetic changes in CoMN_(6)-gra(OH)candidates play a vital role in their ORR catalytic activity.Interestingly,the d-band center can be utilized to well rationalize the ORR catalytic activity.This work highlights the importance of considering the magnetic coupling to well predict the activity of ORR catalysts,and discloses that the manipulation of the magnetic coupling between transition metal atoms is an emerging and powerful approach for the development of high-performance electrocatalysts for ORR and other related reactions.

Room-temperature liquid metal synthesis of nanoporous copper-indium heterostructures for efficient carbon dioxide reduction to syngas

Nanoporous metals show promising performances in electrochemical catalysis.In this paper,we report a self-supporting bimetallic porous heterogeneous indium/copper structure synthesized with a eutectic gallium-indium(EGaIn)material on a copper substrate.This nanoporous copper-indium heterostructure catalyst exhibits excellent performance in the reduction of carbon dioxide to syngas.The ratio of H_(2)/CO is tunable from 0.47 to 2.0 by changing working potentials.The catalyst is highly stable,showing 96%maintenance of the current density after a 70-h continuous test.Density functional theory calculations reveal that the indium/copper interface induces charge redistribution within the copper surface,leading to the formation of two distinct active sites,namely,Cu^(δ)and Cu0,and enabling a high-performance generation of CO and H_(2).This work provides a new strategy for obtaining self-supporting nanoporous metal electrode catalysts.

Two-dimensional Pt_(2)P_(3)monolayer:A promising bifunctional electrocatalyst with different active sites for hydrogen evolution and CO_(2)reduction

Green hydrogen production and CO_(2) fixation have been identified as the fundamental techniques for sustainable economy.The open challenge is to develop high performance catalysts for hydrogen evolution reaction(HER)and CO_(2) electroreduction(CO_(2)ER)to valuable chemicals.Under such context,this work reported computational efforts to design promising electrocatalyst for HER and CO_(2)ER based on the swarm-intelligence algorithm.Among the family of transition-metal phosphides(TMPs),Pt_(2)P_(3) monolayer has been identified as excellent bifunctional catalysts due to high stability,excellent conductivity and superior catalytic performance.Different from typical d-block catalysts,p-band center presented by P atoms within Pt_(2)P_(3) monolayer plays the essential role for its reactivity towards HER and CO_(2)ER,underlining the key value of p-electrons in advanced catalyst design and thus providing a promising strategy to further develop novel catalysts made of p-block elements for various energy applications.

Efficient electrochemical reduction of CO to C_(2) products on the transition metal and boron co-doped black phosphorene

The synthesis of high-value multi-carbon products through the electrochemical reduction of carbon monoxide(COER) is one of the promising avenues for carbon utilization and energy storage,in which searching for efficient electrocatalysts that exhibit moderate CO intermediate binding strength and low kinetic barrier for C-C coupling is a key issue.Herein,by means of comprehensive density functional theory(DFT) computations,we theoretically designed three synergistic coupling catalysts by co-doping transition metal(TM=Fe,Co and Ni) and boron(B) into the two-dimensional black phosphorene(BP),namely TMB@BP for COER to C_(2) products.DFT computations and ab initio molecular dynamics simulations reveal the good stability and high feasibility of these proposed TM-B@BP catalysts for practical applications and future experimental synthesis.More interestingly,high-value ethylene(C_(2)H_(4)),ethane(C_(2)H_(6)) and ethanol(C_(2)H_(5)OH) products can be obtained on these three designed electrocatalysts with ultra-small limiting potentials(-0.20~-0.41 V) and low kinetic energy barriers of C-C coupling(0.52~0.91 eV).Meanwhile,the competitive one-carbon(C_(1)) products and hydrogen evolution reaction can also be effectively suppressed.The promising activity and selectivity of these three designed electrocatalysts render them ideal candidates for CO electroreduction,thus providing a cost-effective opportunity to achieve a sustainable production of high value C_(2) chemicals and fuels.

Phthalocyanine-supported single-atom catalysts as a promising bifunctional electrocatalyst for ORR/OER: A computational study

Developing excellent performance catalysts for the oxygen reduction reaction(ORR)and oxygen evolution re-action(OER)is fundamental for the commercialization of energy transduction and storage equipment.In our works,the potential of plenty of transition metals(TMs)anchored on phthalocyanine(TM-Pc)(TM=Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn,Mo,Ru,Rh,Pd,Ag,Re,Os,Ir,and Pt)as electrocatalysts for the ORR/OER was sys-tematically explored through synthetic density functional theory(DFT)computations.These TM-Pc candidates exhibited high electrochemical stability owing to the intense binding among the anchored TM and the Pc-based substrate.Interestingly,the free energy profiles showed that Ir-Pc can be performed as an outstanding bifunc-tional electrocatalyst for ORR/OER due to its ultralow overpotentials(𝜂ORR=0.46 V and𝜂OER=0.23 V),which can be reasonably explained by energetic and electronic descriptors.The present findings not only expand the database of single-atom catalysts(SACs),but also open the way for the reasonable design and development of advanced electrocatalysts for renewable energy technology.