Rational design of asymmetric atomic Ni-P1N3 active sites for promoting electrochemical CO_(2)reduction

The atomic-level interfacial regulation of single metal sites through heteroatom doping can significantly improve the characteristics of the catalyst and obtain surprising activity.Herein,nickel single-site catalysts(SSCs)with dual-coordinated phosphorus and nitrogen atoms were developed and confirmed(denoted as Ni-PxNy,x=1,2 and y=3,2).In CO_(2)reduction reaction(CO_(2)RR),the CO current density on Ni-PxNy was significantly higher than that of Ni-N4 catalyst without phosphorus modification.Besides,Ni-P1N3 performed the highest CO Faradaic efficiency(FECO)of 85.0%–98.0%over a wide potential range of−0.65 to−0.95 V(vs.the reversible hydrogen electrode(RHE)).Experimental and theoretical results revealed that the asymmetric Ni-P1N3 site was beneficial to CO_(2)intermediate adsorption/desorption,thereby accelerating the reaction kinetics and boosting CO_(2)RR activity.This work provides an effective method for preparing well-defined dual-coordinated SSCs to improve catalytic performance,targetting to CO_(2)RR applications.

Coordinatively unsaturated single Co atoms immobilized on C_(2)N for efficient oxygen reduction reaction

Developing cost-effective and high-efficiency oxygen reduction reaction(ORR)catalysts is imperative for promoting the substantial progress of fuel cells and metal-air batteries.The coordination and geometric engineering of single-atom catalysts(SACs)occurred the promising approach to overcome the thermodynamics and kinetics problems in high-efficiency electrocatalysis.Herein,we rationally constructed atomically dispersed Co atoms on porous N-enriched graphene material C_(2)N(CoSA-C2N)for efficient oxygen reduction reaction(ORR).Systematic characterizations demonstrated the active sites for CoSA-C2N is as identified as coordinatively unsaturated Co-N_(2)moiety,which exhibits ORR intrinsic activity.Structurally,the porous N-enriched graphene framework in C_(2)N could effectively increase the accessibility to the active sites and promote mass transfer rate,contributing to improved ORR kinetics.Consequently,CoSA-C_(2)N exhibited superior ORR performance in both acidic and alkaline conditions as well as impressive long-term durability.The coordination and geometric engineering of SACs will provide a novel approach to advanced catalysts for energy related applications.

Interface electronic engineering of molybdenum sulfide/MXene hybrids for highly efficient biomimetic sensors

Interface regulation plays a key role in the electrochemical performance for biosensors.By controlling the interfacial interaction,the electronic structure of active species can be adjusted effectively at micro and nano-level,which results in the optimal reaction energy barrier.Herein,we propose an interface electronic engineering scheme to design a strongly coupled 1T phase molybdenum sulfide(1T-MoS2)/MXene hybrids for constructing an efficient electrocatalytic biomimetic sensor.The local electronic and atomic structures of the 1T-MoS2/Ti3C2TX are comprehensively studied by synchrotron radiation-based X-ray photoelectron spectroscopy(XPS),as well as X-ray absorption spectroscopy(XAS)at atomic level.Experiments and theoretical calculations show that there are interfacial stresses,atomic defects and adjustable bond-length between MoS2/MXene nanosheets,which can significantly promote biomolecular adsorption and rapid electron transfer to achieve excellent electrochemical activity and reaction kinetics.The 1T-MoS2/Ti3C2TX modified electrode shows ultra high sensitivity of 1.198μA/μM for dopamine detection with low limit of 0.05μM.We anticipate that the interface electronic engineering investigation could provide a basic idea for guiding the exploration of advanced biosensors with high sensitivity and low detection limit.

Asymmetrically coordinated single-atom iron nanozymes with Fe-N_(1)C_(2)structure:A peroxidase mimetic for melatonin detection

Owing to the unique coordination environment and high atom utilization efficiency,single atom catalysts have been considered as an ideal artificial enzyme to mimic natural enzymes.Herein,single-atom Fe nanozyme anchored on N-doped Ti_(3)C_(2)Tx(Fe SA/N-Ti_(3)C_(2)Tx)with asymmetrically coordinated Fe-N_(1)C_(2)configuration is synthesized by vacancy capture and heteroatom doping strategy,which exhibits excellent peroxidase-like activity.Based on the results of peroxidase catalytic kinetics and X-ray adsorption fine spectroscopy,the Fe-N_(1)C_(2)active sites in Fe SA/N-Ti_(3)C_(2)Tx are responsible for the excellent performance.Furthermore,the developed Fe SA/N-Ti_(3)C_(2)Tx can be employed to quantitative detection of melatonin(MT),which shows a wide linear detection range(0.01-100μM)and an excellent detection limit(7.3 nM)in buffer,0.01-100μM and 7.8 nM in serum samples.Our work proves that MXene-based single atoms can be promising nanozyme in the field of bioassays.

Peroxidase-like single Fe atoms anchored on Ti_(3)C_(2)T_(x)MXene as surface enhanced Raman scattering substrate for the simultaneous discrimination of multiple antioxidants

Single-atom nanozymes(SAzymes)are emerging as promising alternatives to mimic natural enzyme,which is due to high atomic utilization efficiency,well-defined geometric,and unique electronic structure.Herein,Fe single atoms supported on Ti_(3)C_(2)T_(x)(Fe-SA/Ti_(3)C_(2)T_(x))with intrinsic peroxidase activity is developed,further constructing a sensitive Raman sensor array for sensing of five antioxidants.Fe-SA/Ti_(3)C_(2)T_(x)shows excellent peroxidase-like performance in catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine(TMB)with colorimetric reactions.X-ray adsorption fine structure(XAFS)reveals that the electron transport between the Ti_(3)C_(2)T_(x)and Fe atoms occurs along Fe-O-Ti ligands,meanwhile the density functional theory(DFT)calculations confirm the spontaneous dissociation of H_(2)O_(2)and the formation of OH radicals.Furthermore,the peroxidase-like Fe-SA/Ti_(3)C_(2)T_(x)was used as surface enhanced Raman scattering(SERS)substrate of oxidized TMB(TMB+)and achieved satisfied signal amplification performance.Using the blocking effects of free radical reactions,one-off identification of 5 antioxidants,including ascorbic acid(AA),uric acid(UA),glutathione(GSH),melatonin(Mel),and tea polyphenols(TPP),could be realized with this high identifiable catalytic property.This principle could realize 100%distinguish accuracy combined with linear discriminant analysis(LDA)and heat map data analysis.A wide detection concentration ranges from 10^(-8)to 10^(-3)M for five antioxidants was also achieved.