Abstract
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.