Precise Modulation of CO 2 ‐to‐Ethanol Conversion by Fully‐Exposed Cu n Clusters Induced by Dangling Bonds in Lacunary Polyoxometalate

ABSTRACT The electrochemical CO 2 reduction toward ethanol under high current density remains challenging. Herein, WO x ‐supported fully exposed Cu clusters (FECCs) confined by hollow mesoporous carbon spheres (HMCS) (Cu‐WO x @HMCS) are fabricated through the “molecular defect confinement” strategy based on the [PW 9 O 34 ] 9− . The [PW 9 O 34 ] 9− features a tri‐lacunary configuration, single‐sided dangling bond characteristics, and excellent liquid‐phase stability, enabling precise anchoring of the {Cu II 6 } cluster to realize atomic dispersion at the molecular level, while enabling the controllable construction of the geometric size and electronic structure of FECCs via Cu─O─W bonds during pyrolysis. The Cu‐WO x @HMCS executes exceptional performance for CO 2 ‐to‐ethanol conversion, with Faradaic efficiencies of 80.6% and 75.3% at partial current densities of 322.4 and 677.7 mA cm −2 , respectively. Mechanism studies reveal the synergistic regulation: (1) The FECCs display a higher Fermi level compared to Cu nanoparticles, acting as a superior electron donor to promote CO 2 adsorption and conversion; moreover, the geometric size effect of FECCs increases the * CO coverage, favoring the C─C coupling. (2) The WO x supplies reactive * H, which favors the hydrogenation of * CO and * CHCOH, steering the asymmetric C─C coupling toward ethanol. This study enables atomic‐level design of catalysts by employing polyoxometalates, delivering a crucial method for precisely constructing fully exposed clusters and highly selective CO 2 RR‐to‐ethanol.