Abstract
A selective noble-metal-free molecular catalyst has emerged as a fruitful approach in the quest for designing efficient and stable catalytic materials for CO2 reduction. In this work, we report that a sodium pectate complex of copper (PG-NaCu) proved to be highly active in the electrocatalytic conversion of CO2 to CH4 in water. Stability and selectivity of conversion of CO2 to CH4 as a product at a glassy carbon electrode were discovered. The copper complex PG-NaCu was synthesized and characterized by physicochemical methods. The electrochemical CO2 reduction reaction (CO2RR) proceeds at −1.5 V vs. Ag/AgCl at ~10 mA/cm2 current densities in the presence of the catalyst. The current density decreases by less than 20% within 12 h of electrolysis (the main decrease occurs in the first 3 h of electrolysis in the presence of CO2). This copper pectate complex (PG-NaCu) combines the advantages of heterogeneous and homogeneous catalysts, the stability of heterogeneous solid materials and the performance (high activity and selectivity) of molecular catalysts.
Highlights
The selectivity and the yields of products of the electrochemical CO2 reduction reaction (CO2RR) at room temperature, as shown by many studies, strongly depend on the material of the working electrode, on which the target reaction takes place, and the solvent used [1,2].The main disadvantages of these heterogeneous electrochemical processes are the need to apply a relatively high potential (~−1.90 V vs. the standard hydrogen electrode (SHE)) and a low current density response
TOh2iRs RaratincdlesiesldecetvivoetelydctontvherstosdCiOum2 tpoeCctHat4eas copmropdleuxctwiinthwcaotperpseorlauntidonitss. catalytic activity in the CO2RR. We discovered that this water-soluItbilse wcaetlallyksnto(wPGn -tNhaatCcuo)pipsehrieglhelcytraocdtievse, ains wtheellCaOs 2nRaRnoasntdruscetluercetdivceolyppcoenr vaenrdtscCopOp2er tooCxHid4eass, proomduoctet itnhewealteecrtrsoocluataiolyntsi.c conversion of CO2 to deep reduced products such as meItthiasnwe,eellthkynloewnen, athnadt ectohpapneorle[l1e,2ct5r–o2d7e].s,Haoswweevllear,stnhaenreoastrreuactnuurmedbceorpopf erxamndplceospopfetrhe oxeidleecst,ropcraotmaloyteictchoenevlercstrioncaotaf lCyOtic2 ctonCvHer4s,iCon2Ho4f,CCO2O2 t4oodneseipngreledcuocpedpeprrioodnusc[t2s8s–u3c2h]. aTshe memthoastnceo, emthmyolennme,eacnhdanetihsmanofl s[1u,c2h5–d2e7e]p
Na and Cu concentrations were identified in the complex extract using simultaneous inductively coupled plasma optical emission spectrometer (ICP-OES) model iCAP 6300 DUO by Thermo Fisher Scientific Company (168 Third Avenue, Waltham, MA 02451, USA) equipped with a CID detector
Summary
The selectivity and the yields of products of the electrochemical CO2 reduction reaction (CO2RR) at room temperature, as shown by many studies, strongly depend on the material of the working electrode, on which the target reaction takes place, and the solvent used [1,2]. The low value of the peak current is explained by the slow diffusion of the PG-NaCu molecules to the working electrode due to their large size and high molecular weight. Such a system can be called pseudo-homogeneous, and it combines the advantages of homogeneous and heterogeneous systems. WWhheennaannaaqquueeoouussssoolulutitoionnisisssaattuurraatteeddwwiitthhccaarrbboonnddiiooxxiiddee,, tthhee EEoonnsestetbbeceocommeesseeqquuaal l tidotroee−d−1rue.11dc5.tu1io5VcntVi(,oba(nlbnu,ldeuaneacdutcuaravrtpveaoeitnpienonFttFieigiangultuoriarefel−8o8))f1aa.−5nn10dd.5Vc0c,ootVrrhrr,eeetsshcppueoorcnrnueddnrssrtettdonoetttnhhdseeeitniiynnsieiitttxiyiacaleelpexpodcoetsteee1ndn4tsitami1al4lAoofm/fccAacmar/brc2bom, onw2n,dhwdiioliehxoitixldhe-ee thaemaomunotuonft PoGf P-NGa-CNuaCinutihne tehleecetrleocdteroids eonislyo0n.l1yμ0g.1oμf gthoefstuhbestsaunbcset.aTnchee.reThisearelsoisaalssloighat slsihgihftt isnhitfhteinCtuh(eIIC)/uC(IuI()I/C) rue(dI)urcetidouncptieoankpteoawkatrodws anredgsantievgeaptiovteenptoiatelsn.tials
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