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.

Ionic liquid assisted electrochemical coating zinc nanoparticles on carbon cloth as lithium dendrite suppressing host

The application of lithium metal anode with high specific capacity and energy density is limited by the volume expansion and pulverization caused by dendrite growth during cycle process.We propose a composite lithium anode by immersing molten lithium on the flexible three-dimensional(3D)carbon cloth scaffold with the zinc nanoparticles.The lithiophilic zinc nanoparticles layer of framework is synthesized by fast and easy electrochemical deposition from ionic liquid avoiding high temperature,high pressure and toxic reagent.The lithium is infused into the 3D lithiophilic framework,the composite anode is obtained.The steady network structure can confine the lithium and lead to Li dendrite restraining and reducing volume change due to the low interfacial resistance and reduce the effective current density,which induced the homogeneous Li growth.Benefiting from this,the Li infused 3D carbon cloth-Zn symmetric battery exhibits a low stripping/plating overpotential(~30 mV)and can be stable over 900 h at 1 mA cm-2.The Li//LiFePO4 battery delivers higher reversible capacity(140 mAh g^-1 at 2 C and 120 mAh g^-1 at 5 C)and stable cycling for 1500 and 2000 cycles than bare Li.

A n-Si/CoOx/Ni:CoOOH photoanode producing 600 mV photovoltage for efficient photoelectrochemical water splitting

n-Si,believed as a promising photoanode candidate,has suffered from sluggish oxygen evolution reaction(OER)kinetics and poor chemical stability when exposed to aqueous electrolyte.Herein,CoO_(x)/Ni:CoOOH bilayers were successfully deposited on n-Si substrate by atomic layer-deposition(ALD)and photoassisted electrochemical deposition(PED)for stabilizing and catalyzing photoelectrochemical(PEC)water oxidation.In comparison to the n-Si/CoO_(x)photoanode as reference,the prepared n-Si/CoO_(x)/Ni:CoOOH photoanode upon the optimized PED process presents a much improved PEC performance for water splitting,with the onset potential cathodically shifted to~1.03 V vs.reversible hydrogen electrode(RHE)and the photocurrent density much increased to 20 mA cm^(−2)at 1.23 V vs.RHE.It is revealed that the introduction of Ni dopants increases the work functions of the deposited Ni:CoOOH overlayers,which gives rise to the upward band bending weakened at the n-Si/CoO_(x)/Ni:CoOOH cascading interface while strengthened at the Ni:CoOOH/electrolyte interface(with the band bending shifted from downward to upward),contributing to the decreased and the increased driving forces for charge transfer at the interfaces,respectively.Then,the balanced driving forces at the interfaces would endow the n-Si/CoO_(x)/Ni:CoOOH photoanode with the best PEC performance.Moreover,PED has been evidenced superior to ED to dope Ni into CoOOH with the formed overlayer effectively catalyzing and stabilizing PEC water splitting.