Highly selective electrocatalytic reduction of CO2 to HCOOH over an in situ derived hydrocerussite thin film on a Pb substrate

A metal oxide electrode has been developed for the electrochemical CO 2 reduction reaction (eCO 2 RR). It exhibits superior activity and product selectivity towards eCO 2 RR by circumventing the previously encountered problem of self-reduction with high-valence metals. Specifically, a hydrocerussite [Pb 3 (CO 3 ) 2 (OH) 2 ] thin film has been synthesized in situ on a Pb substrate (denoted as ER-HC) by an electroreduction method using a lead-based metal–organic framework (Pb-MOF) as a precursor. The ER-HC electrode exhibits a high selectivity of 96.8% towards HCOOH production with a partial current density of 1.9 mA cm −2 at −0.88 V vs. the reversible hydrogen electrode (RHE). A higher HCOOH partial current density of 7.3 mA cm −2 has been achieved at −0.98 V vs. RHE. Physicochemical and electrochemical characterization results demonstrate that the defective hydrocerussite surface exhibits appropriate adsorption free energy of formate (HCOO − ) and a lower reaction free energy for HCOOH production from CO 2 , which greatly boosts the eCO 2 RR activity and HCOOH production selectivity. The structure and eCO 2 RR performance of the hydrocerussite thin film remain stable in 0.1  M KHCO 3 as electrolyte, ensuring its durability. Overall, this work not only provides a metal oxide electrode (metal hydroxide, to be more precise) with excellent eCO 2 RR performance, but also expands the in situ electrochemical derivatization strategy for the fabrication of metal oxide electrodes.