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.

Polyacrylate modified Cu electrode for selective electrochemical CO_(2) reduction towards multicarbon products

Highly selective production of value-added multicarbon(C^(2+))products via electrochemical CO_(2) reduction reaction(eCO_(2)RR)on polycrystalline copper(Cu)remains challenging.Herein,the facile surface modification using poly(α-ethyl cyanoacrylate)(PECA)is presented to greatly enhance the C^(2+)selectivity for eCO_(2)RR over polycrystalline Cu,with Faradaic efficiency(FE)towards C^(2+)products increased from30.1%for the Cu electrode to 72.6%for the obtained Cu-PECA electrode at-1.1 V vs.reversible hydrogen electrode(RHE).Given the well-determined FEs towards C^(2+)products,the partial current densities for C^(2+)production could be estimated to be-145.4 mA cm~(-2)for the Cu-PECA electrode at-0.9 V vs.RHE in a homemade flow cell.In-situ spectral characterizations and theoretical calculations reveal that PECA featured with electron-accepting-C≡N and-COOR groups decorated onto the Cu electrode could inhibit the adsorption of^(*)H intermediates and stabilize the^(*)CO intermediates,given the redistributed interfacial electron density and the raised energy level of d-band center(E_(d))of Cu active sites,thus facilitating the C-C coupling and then the C^(2+)selective production.This study is believed to be guidable to the modification of electrocatalysts and electrodes with polymers to steer the surface adsorption behaviors of reaction intermediates to realize practical eCO_(2)RR towards value-added C^(2+)products with high activity and selectivity.

Modulating redox transition kinetics by anion regulation in Ni-Fe-X(X=O,S,Se,N,and P)electrocatalyst for efficient water oxidation

NiFe-based electrocatalysts will experience dynamical surface reconstruction during oxygen evolution reaction(OER)process,and the derived metal(oxy)hydroxide hybrids on the surface have been considered as the actual active species for OER.Tremendous efforts have been dedicated to understanding the surface reconstruction,but there is rare research on recognizing the origin of improved performance derived from anion species of substrate.Herein,the OER electrocatalytic characteristics were tuned with different anions in NiFe-based catalyst,using NiFe-based oxides/nitride/sulfide/selenides/phosphides(NiFeX,X=O,N,S,Se,and P)as the model materials.The combination of X-ray photoelectronic spectroscopy,electrochemical tests,operando spectroscopic characterizations,and density functional theory(DFT)calculations,reveals that anion with lower electronegativity in NiFe-based catalyst leads to higher conductivity and delayed valence transition of Ni sites,as well as optimized adsorption behavior towards oxygen intermediates,contributing to enhanced OER performance.Accordingly,NiFeP electrocatalyst demonstrates an ultralow overpotential of 265 mV at 20 mA·cm−2 for OER,as well as long-term stability.This work not only offers further insights into the effect of anionic electronegativity on the intrinsic OER electrocatalytic properties of NiFe-based electrocatalyst but also provides guide to design efficient non-noble metal-based electrocatalysts for water oxidation.