Abstract
The large‐scale application of electrochemical reduction of CO2, as a viable strategy to mitigate the effects of anthropogenic climate change, is hindered by the lack of active and cost‐effective electrocatalysts that can be generated in bulk. To this end, SnO2 nanoparticles that are prepared using the industrially adopted flame spray pyrolysis (FSP) technique as active catalysts are reported for the conversion of CO2 to formate (HCOO−), exhibiting a FEHCOO − of 85% with a current density of −23.7 mA cm−2 at an applied potential of −1.1 V versus reversible hydrogen electrode. Through tuning of the flame synthesis conditions, the amount of oxygen hole center (OHC; Sn≡O●) is synthetically manipulated, which plays a vital role in CO2 activation and thereby governing the high activity displayed by the FSP‐SnO2 catalysts for formate production. The controlled generation of defects through a simple, scalable fabrication technique presents an ideal approach for rationally designing active CO2 reduction reactions catalysts.
Highlights
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It can be observed that a higher feed-rate during flame spray pyrolysis (FSP) results in increasing particle sizes of the FSP-SnO2 which is consistent with the X-ray diffraction (XRD) and N2 adsorptiondesorption results, vide infra
Summary
In order to systematically control the morphology and surface properties of SnO2, FSP was utilized. FSP-SnO2-5 was thermally annealed in air (referred as HT-FSPSnO2-5) to reduce the amount of OHC This control sample was evaluated for CO2RR (Figure S13, Supporting Information) and we can clearly demonstrate that the removal of defects (as observed from EPR spectra and the corresponding double integrated intensity, Figure S14, Supporting Information) leads to decreased formate production, in line with our hypothesis. It is well established that the application of bias during CO2RR with SnO2 catalysts leads to partial reduction of oxide layers to generate SnOx sites.[56,57] The removal of O from defected SnO2 lattice during in situ reduction of the catalyst results in increasing the oxygen vacancies To understand this changing defect structure under applied potentials, in situ Raman spectroscopy (detailed, Supporting Information) was carried out with FSP-SnO2-5. These findings illustrate the ability to potentially tune CO2RR properties through synthetic manipulation of FSP conditions to optimizing for surface area and defect density
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