Revealing structural evolution of PbS nanocrystal catalysts in electrochemical CO2 reduction using in situ synchrotron radiation X-ray diffraction

Abstract

We investigated the structural evolution of PbS catalysts under electrochemical CO₂ reduction reaction (eCO₂RR) conditions using an in situ synchrotron radiation X-ray diffraction (SR-XRD) technique. The PbS catalyst with an initial form of size-tunable nanocrystals (NCs) performed efficiently in the electrochemical conversion of CO₂ to formate with a record-high mass activity (MA) of 52.2 ± 5.2 mA mg_Pb⁻¹ at −1.2 V and 74.9 ± 4.7 mA mg_Pb⁻¹ at −1.4 V vs. the reversible hydrogen electrode (RHE). In situ SR-XRD analyses revealed that PbS NCs underwent rapid structural transformation to Pb thin films during the eCO₂RR, providing the real catalytic surface for the eCO₂RR. Such a structural change is complex, with PbS first being converted to PbCO₃ and the latter species being further reduced to Pb. This work highlights the importance of understanding environmental impacts on the instability of nanocatalysts under eCO₂RR conditions and the need for designing more robust electrocatalysts.