Zns Atomic Layer-modified Ultrathin Zn Nanosheets For Effective CO₂ Reduction

Electrochemical reduction of CO₂ into value-added chemicals provides a facile solution to energy and environment crisis.Due to the sluggish reaction kinetics of CO₂ reduction,efficient and robust electrocatalysts are highly required to accelerate this reaction?Non-precious metals were identified as promising catalysts for the practical application of reduction of CO₂.Nevertheless,they usually suffer from poor electrocatalytic performance,such as large overpotential and low selectivity,which may originate from the inappropriate adsorption energy of intermediates of CO₂reduction.The modification of catalysts with heteroatoms,functional groups,and adion is successful in tuning their adsorption energy,thus boosting the intrinsic property for CO₂ reduction.However,these residual heteroatoms were gradually lost during the electroreduction process,leading to a poor long-term durability.Here we report that a conceptually new electrocatalyst,Zn nanosheet coated with porous ZnS subnanometer layer,can achieve excellent catalytic performance.1.We synthesize a novel ZnS/Zn/ZnS?S-Zn-S?sandwich nanostructure consisting of inner Zn NSs?4 nm in thickness and several microns in the lateral size?and ZnS porous subnanometer layer?0.68 nm in thickness?via chemical vapor deposition.2.The experimental investigations demonstrate that the S-Zn-S catalyst achieves⁹4.2%Faradaic efficiency of CO at-0.8 V?vs.RHE?,overwhelming all Zn-based electrocatalysts and even overtaking noble-metal catalysts.Moreover,the S-Zn-S catalyst exhibits high long-term durability,the Faradaic efficiency keeps above 90%after 15 h testing while the current density remains unchanged.The structure and composition of S-Zn-S NSs kept unchanged after electrochemical reduction.3.We identify the active sites for CO₂ reduction via a comparative study of S-Zn-S NSs,ZnS layer,Zn@ZnS NSs,and Zn NS.On the basis of the performance comparation,we can deduce that the active sites should locate in Zn NSs,and ZnS layer can promote CO production.The ZnS atomic layer acts as a modification,enhancing the intrinsic activity of Zn,increasing the TOF by a factor of three,and the CO₂ molecule is more easily activated.4.Theoretical investigations demonstrate that the ZnS layer on the Zn NSs can enhance the adsorption of intermediates*COOH,resultantly,the energy barrier is lowered.Due to the simple synthetic process,this strategy is expected to apply to more low-cost metal materials for highly active and stable catalysts.