Densely Packed, Ultra Small SnO Nanoparticles for Enhanced Activity and Selectivity in Electrochemical CO₂ Reduction

Abstract

Controlling the selectivity in electrochemical CO 2 reduction is an unsolved challenge.While tin (Sn) has emerged as apromising non-precious catalyst for CO 2 electroreduction, most Sn-based catalysts produce formate as the major product, which is less desirable than CO in terms of separation and further use.T in monoxide (SnO) nanoparticles supported on carbon black were synthesized and assembled and their application in CO 2 reduction was studied. Remarkably high selectivity and partial current densities for CO formation were obtained using these SnO nanoparticles compared to other Sn catalysts.The high activity is attributed to the ultra-small sizeof the nanoparticles (2.6 nm), while the high selectivity is attributed to al ocal pH effect arising from the dense packing of nanoparticles in the conductive carbon black matrix.Electrochemical reduction of CO 2 to form carbon-based fuels and chemicals has been widely proposed for the storage and utilization of intermittent renewable energies such as solar and wind.[1] However,t wo major deficiencies have prevented CO 2 electroreduction from becoming av iable technology:energy inefficiencyowing to large overpotentials, and poor selectivity leading to separation issues.T herefore, there is tremendous interest in developing active and selective electrocatalysts for CO 2 reduction. In terms of electrochemical activity,n oble-metal catalysts rank the best.[2] Among non-noble metal catalysts,S n-based catalysts stand out. [3,4] However,the major CO 2 reduction product using Sn catalysts is formate (HCOO À ), and CO is generated only in as mall amount.[5] Unlike its acidic form, formic acid which is ahighvalue chemical, formate has no obvious usage and is difficult to separate and convert into other high-value products without adding costly processes.C O, on the other hand, is ah ighly desirable product as it is ag as that can be easily separated and further converted into fuels and bulk chemicals at al arge scale through existing chemical technologies. Achieving high activity and selectivity for CO formation on anon-precious catalyst such as Sn is therefore anotable goal with practical relevance.TheC O 2 electroreduction performance of Sn based catalysts developed recent years is summarized in the Supporting Information, Figure S4. Modulation of size, shape,a nd composition (metal, oxide,o rs ulfide) of monometallic Sn catalysts is effective to achieve high formate formation activity,but these approaches cannot improve CO formation performance.[5a-d] Until now,c ooperative promotion is required to enhance CO formation on Sn-based catalysts.For example,Cu-Sn bimetallic catalysts are reported to favor CO formation; [6] however, Cu also acts as possible catalytic sites.H erein we report an ew strategy that leads to unprecedented activity and selectivity for CO formation among monometallic Sn catalysts.K ey to this performance are the ultra-small size of catalyst nanoparticles and their dense packing in ac onductive matrix, which lead to ah igh density of active s...

Boosting Formate Production from CO2 at High Current Densities Over a Wide Electrochemical Potential Window on a SnS Catalyst

“…A detailed performance comparison between this work and other published Sn‐based electrocatalysts for CO 2 reduction to formate is presented in Figure and Table S1 (Supporting Information). [ 10–14,22a,25,30,31 ] The potential window across −0.5 V to −1.5 V with FE formate over 70% obtained from this work is clearly broader than literature studies that typically display “volcano shape” characteristic. Li et al.…”

“…To overcome the intrinsically poor electrocatalytic CO 2 reduction performance of a bulk Sn with a large overpotential and low current density, various material engineering strategies have been applied. This includes nanostructuring of Sn to structures such as metallic Sn quantum sheets, [ 10 ] coralline structured SnO x , [ 11 ] SnO 2 porous nanowires, [ 12 ] ultrasmall SnO, [ 13 ] and SnS 2 nanosheets, [ 14 ] that promotes surface area and active sites toward selective formate production. In addition to alloying or doping with metals, such as copper, [ 15 ] silver, [ 16 ] palladium, [ 17 ] nickel, [ 18 ] positive synergetic impact of doping of a nonmetallic element, such as sulfur [ 19 ] or nitrogen [ 20 ] is another attractive approach toward enhancing formate production.…”

Nanoparticle‐Based Electrodes with High Charge Transfer Efficiency through Ligand Exchange Layer‐by‐Layer Assembly

“…Increasing the packing density of functional NPs within a limited electrode volume is challenging in electrodes for energy storage [115][116][117][118] and other integrated nanostructures. [57,[119][120][121] Generally, NP-based electrodes with a high mass density cannot be easily achieved by conventional electrode preparation methods such as doctor blading or electrostatic LbL assembly without additional treatments (e.g., the use of a mechanical press or thermal annealing) due to the low-density nature of polymeric (or carbonaceous) materials and electrostatic repulsive forces among NPs with the same charge. [94,101,[122][123][124] On the other hand, it has been reported that in situ LE-LbL assembly can produce densely packed NP multilayers without any NP agglomeration or segregation because the reported approach does not use charged species and/or bulky polymer ligands in organic media.…”

Cathodized copper porphyrin metal–organic framework nanosheets for selective formate and acetate production from CO2 electroreduction

“…However, the formate and acetate production from the CO 2 RR still remains a scientific challenge 22. Major Sn-based catalysts usually suffer from limited reaction selectivity and a narrow range of active voltage,23–25 although a recent Bi-based catalyst has shown high potential for formate generation 26,27. In addition, very few electrocatalysts perform CO 2 reduction to acetate due to the low activity of C–C coupling 28.…”