Self-supported ultrathin NiCo layered double hydroxides nanosheets electrode for efficient electrosynthesis of formate

Electrochemical CO_(2)reduction into energy-carrying compounds,such as formate,is of great importance for carbon neutrality,which however suffers from high electrical energy input and liquid products crossover.Herein,we fabricated self-supported ultrathin NiCo layered double hydroxides(LDHs)electrodes as anode for methanol electrooxidation to achieve a high formate production rate(5.89 mmol h^(-1)cm^(-2))coupled with CO_(2)electro-reduction at the cathode.A total formate faradic efficiency of both anode for methanol oxidation and cathode for CO_(2)reduction can reach up to 188%driven by a low cell potential of only 2.06 V at 100 mA cm^(-2)in membrane-electrode assembly(MEA).Physical characterizations demonstrated that Ni^(3+)species,formed on the electrochemical oxidation of Ni-containing hydroxide,acted as catalytically active species for the oxidation of methanol to formate.Furthermore,DFT calculations revealed that ultrathin LDHs were beneficial for the formation of Ni^(3+)in hydroxides and introducing oxygen vacancy in NiCo-LDH could decrease the energy barrier of the rate-determining step for methanol oxidation.This work presents a promising approach for fabricating advanced electrodes towards electrocatalytic reactions.

Tandem electrocatalysis for CO_(2) reduction to multi-carbons

The rising CO_(2) concentration in the atmosphere due to extensive use of fossil fuels has led to serious climate and environmental issues. One efficient solution is that CO_(2) capture from industrial emissions followed its conversion into value-added chemicals driven by renewable energies. CO_(2) electroreduction(CO_(2) RR) features a green and sustainable fashion towards effective CO_(2) conversion, but still suffers from low multi-carbon selectivity and yield. Considering the pivotal role of CO intermediate in C–C coupling to multi-carbon formation, tandem CO_(2) RR systems with separated CO generation and consumption components could facilitate the coupling between *CO-based intermediates to energy-intensive multi-carbons by manipulating CO diffusion and surface coverage. In this aspect, we comprehensively reviewed the design principles of tandem systems for CO_(2) electroreduction reaction. The chemistry behind the C–C coupling regarding to their distribution and diffusion was initially introduced, which was followed by achievements on tandem architectures, from catalysts, electrodes to systems. Future directions and perspectives on advanced tandem system designs for CO_(2) RR were discussed at the end. This review contributes to the understanding of structureperformance correlations in tandem catalysis and helps guide the effective collection of multi-carbons of high-yield and highselectivity.

Structure evolution,dielectric,and conductivity behavior of(K_(0.5)Na_(0.5))NbO_(3)-Bi(Zn_(2/3)Nb_(1/3))O_(3) ceramics

(1-x)K_(0.5)Na_(0.5)Nb0_(3-x)Bi(Zn_(2/3)Nb_(1/3))0_(3)((1-x)KNN-xBZN,x=0.010,0.015,0.020,0.025,and 0.030)lead-free ceramics were fabricated via a traditional solid-state method.The crystal structure,microstructure,dielectric,and conductivity behavior of this system were studied.Combined with X-ray diffraction(XRD)patterns,Rietveld refinement,and dielectric spectroscopy,an orthorhombic phase was determined for x=0.010,an orthorhombic-tetragonal mixed phase was identified for x=0.015,and a rhombohedral symmetry appears in 0.020≤x≤0.030.Both 0.98KNN-0.02BZN and 0.975KNN-0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent(tan)in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to cubic.The activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly,then drop sharply,and finally decline slowly,which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.

Influence of interface point defect on the dielectric properties of Y doped CaCu_(3)Ti_(4)O_(12) ceramics

CaCu_(3)Ti_(4-x)Y_(x)O_(12)(0≤x≤0.12)ceramics were fabricated with conventional solid-state reaction method.Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM),respectively.The impedance and modulus tests both suggested the existence of two different relaxation behavior,which were attributed to bulk and grain boundary response.In addition,the conductivity and dielectric permittivity showed a step-like behavior under 405 K.Meanwhile,frequency independence of dc conduction became dominant when above 405 K.In CCTO ceramic,rare earth element Y^(3+)ions as an acceptor were used to substitute Ti sites,decreasing the concentration of oxygen vacancy around grainelectrode and grain boundary.The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.