Defect Engineering on Carbon‑Based Catalysts for Electrocatalytic CO2 Reduction

Electrocatalytic carbon dioxide(CO2)reduction(ECR)has become one of the main methods to close the broken carbon cycle and temporarily store renewable energy,but there are still some problems such as poor stability,low activity,and selectivity.While the most promising strategy to improve ECR activity is to develop electrocatalysts with low cost,high activity,and long-term stability.Recently,defective carbon-based nanomaterials have attracted extensive attention due to the unbalanced electron distribution and electronic structural distortion caused by the defects on the carbon materials.Here,the present review mainly summarizes the latest research progress of the construction of the diverse types of defects(intrinsic carbon defects,heteroatom doping defects,metal atomic sites,and edges detects)for carbon materials in ECR,and unveil the structure-activity relationship and its catalytic mechanism.The current challenges and opportunities faced by high-performance carbon materials in ECR are discussed,as well as possible future solutions.It can be believed that this review can provide some inspiration for the future of development of high-performance ECR catalysts.

Two-Dimensional Organometallic TM3–C12S12 Monolayers for Electrocatalytic Reduction of CO2

Organometallic nanosheets are a versatile platform for design of efficient electrocatalyst materials due to their high surface area and uniform dispersion of metal active sites.In this paper,we systematically investigate the electrocatalytic performance of the first transition metal series TM3–C12S12 monolayers on CO2 using spin-polarized density functional theory.The calculations show that M3–C12S12 exhibits excellent catalytic activity and selectivity in the catalytic reduction in CO2.The main reduction products of Sc,Ti,and Cr are CH4.V,Mn,Fe and Zn mainly produce HCOOH,and Co produces HCHO,while CO is the main product for Ni and Cu.For Sc,Ti,and Cr,the overpotentials are>0.7 V,while for V,Mn,Fe,Co,Ni,Cu,Zn,the overpotentials are very low and range from 0.27 to 0.47 V.Therefore,our results indicate that many of the M3–C12S12 monolayers are expected to be excellent and efficient CO2 reduction catalysts.

Heterophase engineering of SnO2/Sn3O4 drives enhanced carbon dioxide electrocatalytic reduction to formic acid

Sn-based electrocatalysts have been gaining increasing attention due to their potential contribution in the conversion of CO2 into HCOOH driven by sustainable energy sources;however,their actual capability to catalyze CO2 reduction reaction(CO2RR)still cannot meet the requirements of commercial-scale applications.Therefore developing Snbased catalyst is of vital importance.Herein,the sheet-like heterophase Sn O2/Sn3O4 with a high density of phase interfaces has been first engineered by a facile hydrothermal process,with Sn3O4 as the dominant phase.The evidences from experiments and theoretical simulation indicate that the charge redistribution and built-in electric field at heterophase interfaces boost CO2 adsorption and HCOO*formation,accelerate the charge transfer between the catalysts and reactants,and ultimately greatly elevate the intrinsic activity of the heterophase Sn O2/Sn3O4 towards CO2 RR.Meanwhile,the in-situ generated porous structure and metal Sn during CO2 RR improve the mass transmission within the interlayer volume and the conductivity of Sn O2/Sn3O4.The heterophase Sn O2/Sn3O4 displays high activity and selectivity for CO2 RR,achieving an improvement in CO2 reduction current density,88.3%Faradaic efficiency of HCOOH conversion at-0.9 VRHE,along with a long-term tolerance in CO2 RR.This study demonstrates that heterophase interface engineering is an efficient strategy to regulate advanced catalysts for different applications.

Theoretical insight into the selectivities of copper-catalyzing heterogeneous reduction of carbon dioxide

The chemical reduction of carbon dioxide(CO2) has always drawn intensive attentions as it can not only remove CO2 which is the primary greenhouse gas but also produce useful fuels. Industrial synthesis of methanol utilizing copper-based catalysts is a commonly used process for CO2 hydrogenation. Despite extensive efforts on improving its reaction mechanism by identifying the active sites and optimizing the operating temperature and pressure, it is still remains completely unveiled. The selectivities of CO2 electroreduction at copper electrode could mainly be towards carbon monoxide(CO), formic acid(HCOOH), methane(CH4) or ethylene(C2H4), which depends on the chemical potentials of hydrogen controlled by the applied potential. Interestingly, methanol could hardly be produced electrochemically despite utilizing metallic copper as catalysts in both processes. Moreover, the mechanistic researches have also been performed aiming to achieve the higher selectivity towards more desirable higher hydrocarbons. In this work, we review the present proposals of reaction mechanisms of copper catalyzing CO2 reduction in industrial methanol synthesis and electrochemical environment in terms of density functional theory(DFT) calculations, respectively. In addition, the influences of the simulation methods of solvation and electrochemical model at liquid-solid interface on the selectivity are discussed and compared.

Comparable electrocatalytic performances of carbon-and Rh-loaded SrTiO_3 nanoparticles

Carbon-and Rh-loaded strontium titanate（SrTiO3） nanoparticles（NPs） were synthesized respectively by the wet impregnation method and the aerobic and anaerobic ethanol oxidation methods, and characterized by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction crystallography, UV–vis absorption, Raman spectroscopy, and X-ray photoelectron spectroscopy. Carbon was shown to be uniformly coated on SrTiO3 NPs by the aerobic and anaerobic ethanol oxidation methods Electrocatalytic activities of unmodified and modified SrTiO3 NPs were tested for water splitting and CO2 reduction. The aerobic C-coated and Rh-loaded SrTiO3 catalysts showed comparable activity that was increased by 〉10-fold of that of unmodified SrTiO3 catalyst. These results demonstrate that both metallic and nonmetallic surface modifications can highly improve the electrocatalytic activity of SrTiO3 NPs and point to highlight a more important role of the modifier in the electrocatalytic reactions than of the SrTiO3 structure.