Chalcogen heteroatoms doped nickel-nitrogen-carbon single-atom catalysts with asymmetric coordination for efficient electrochemical CO_(2) reduction

The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2) reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N_(4)-C)configuration to obtain Ni-X-N_(3)-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N_(3)-C(X:S,Se,and Te)SACs,Ni-Se-N_(3)-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98% at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2) battery integrated with Ni-Se-N_(3)-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm^(-2) and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N_(4)-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N_(3)-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of ^(*)COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.

Asymmetrically coordinated main group atomic In-S_(1)N_(3)interface sites for promoting electrochemical CO_(2)reduction

Designing catalysts with highly active,selectivity,and stability for electrocatalytic CO_(2)to formate is currently a severe challenge.Herein,we developed an electronic structure engineering on carbon nano frameworks embedded with nitrogen and sulfur asymmetrically dual-coordinated indium active sites toward the efficient electrocatalytic CO_(2)reduction reaction.As expected,atomically dispersed In-based catalysts with In-S_(1)N_(3)atomic interface with asymmetrically coordinated exhibited high efficiency for CO_(2)reduction reaction(CO_(2)RR)to formate.It achieved a maximum Faradaic efficiency(FE)of 94.3%towards formate generation at−0.8 V vs.reversible hydrogen electrode(RHE),outperforming that of catalysts with In-S2N2 and In-N4 atomic interface.And at a potential of−1.10 V vs.RHE,In-S_(1)N_(3)achieves an impressive Faradaic efficiency of 93.7%in flow cell.The catalytic performance of In-S_(1)N_(3)sites was confirmed to be enhanced through in-situ X-ray absorption near-edge structure(XANES)measurements under electrochemical conditions.Our discovery provides the guidance for performance regulation of main group metal catalysts toward CO_(2)RR at atomic scale.

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.

Working-in-tandem mechanism of multi-dopants in enhancing electrocatalytic nitrogen reduction reaction performance of carbon- based materials

Developing carbon-based electrocatalysts with excellent N2 adsorption and activation capability holds the key to achieve highly efficient nitrogen reduction reaction(NRR)for reaching its practical application.Here,we report a highly active electrocatalyst--metal-free pyrrolic-N dominated N,S co-doped carbon(pyrr-NSC)for NRR.Based on theoretical and experimental results,it is confirmed that the N and S-dopants practice a working-in-tandem mechanism on pyrr-NSC,where the N-dopants are utilized to create electropositive C sites for enhancing N2 adsorption and the S-dopants are employed to induce electron backdonation for facilitating N2 activation.The synergistic effect of the pyrrolic-N and S-dopants can also suppress the irritating hydrogen evolution reaction,further boosting the NRR performance.This work gives an indication that the combination of two different dopants on electrocatalyst can enhance NRR performance by working in the two tandem steps-the adsorption and activation of N2 molecules,providing a new strategy for NRR electrocatalyst design.

酵母催化2-辛酮不对称还原反应特性与醇脱氢酶基因表达水平的关联性研究

研究通过介质工程,选择4种Log P值(分配系数的对数值)的有机溶剂,采用气相色谱技术检测有机溶剂对酿酒酵母催化2-辛酮不对称还原反应的催化活性与反应选择性的影响,并通过荧光定量PCR(RT-PCR)检测不同水/有机溶剂两相体系下YADH1与YADH2基因表达情况,旨在探究不同水/有机溶剂两相体系与酿酒酵母催化2-辛酮不对称还原反应特性的关系,并考察其反应特性与YADH基因的表达水平之间是否存在关联,试图从基因表达水平解释不同有机介质中酵母催化羰基不对称还原特性的内在机制,从而为获得重要手性中间体(S)-2-辛醇产物提供理论指导。分析结果表明,不同水/有机溶剂两相体系对酿酒酵母催化2-辛酮羰基不对称还原反应的催化活性与反应选择性有较大影响,其中,催化活性在水/有机溶剂两相体系比单水相体系降低,但反应选择性却有较大提高(甲苯除外),而且log P值(分配系数的对数值)越大,产物对映体过量(Enantiomeric excess,e.e)值也越大。进一步研究表明,YADH基因表达水平与酵母羰基不对称还原反应特性有重要关联,YADH基因表达水平与酵母催化活性呈正相关,但与反应选择性呈负相关。