Enhanced electron delocalization induced by p-p-d orbital coupling for high-rate formic acid electrosynthesis

Abstract The electroreduction of carbon dioxide (CO2RR) to high-value-added formic acid (HCOOH) is of great significance for closing the anthropogenic CO2 cycle. Bismuth oxide (Bi2O3) possesses Biδ+ sites that is favorable for oxygenate intermediate (i.e. *OCHO) adsorption, while the competitive hydrogen evolution reaction is also facilitated, inhibiting broad-range high selectivity. In this work, we propose to build an ultrathin Bi2WO6 nanosheets (NSs) with Aurivillius-phase for enhancing electronic delocalization of Biδ+ by 5d (Bi)−2p (O)−6p (W) orbital coupling. The delocalized Biδ+ sites could boost the coupling between the O 2p orbital of *OCHO and the Bi 6p orbital that promotes *OCHO adsorption and electron transfer from Biδ+ to the *OCHO intermediate, thereby improving the CO2RR performance and maintaining structure. In situ Raman spectroscopy and theoretical calculations demonstrated that delocalized Biδ+ could optimize the structure of interfacial water and decrease the *H coverage for restraining by-product H2 production. As a result, these advantages endowed the Bi2WO6 NSs with high HCOOH selectivity of 97.8% and peak partial current density of 877 mA cm–2, superior to pristine Bi2O3 and Aurivillius-phase bismuth molybdate NSs.