Ordered Hollow Sphere Array Nanoreactors for Direct Electroreduction of Diluted CO₂ Into Ethylene

Direct electroreduction of industrially diluted CO₂ into C₂H₄ represents a promising route for sustainable energy conversion, yet the selectivity and current density of this process are fundamentally constrained by the insufficient reactant concentration and generation of *CO intermediates. Herein, we addressed this issue by designing an ordered hollow sphere array nanoreactor with Cu nanoparticle and Ni single atom as the tandem catalytic sites (Cu-NP/Ni-NC OHSpA) using a unique reverse templating protocol. Mechanistic studies demonstrate that *CO can be generated on Ni site and undergoes spillover to the neighboring Cu particle. Significantly, the ordered hollow sphere array serves as effective CO reservoir to enhance the *CO coverage and thereby promote the C-C coupling to form C₂H₄. As a consequence, Cu-NP/Ni-NC OHSpA exhibits excellent electrocatalytic performance toward the conversion of diluted CO₂ (i.e., 15% CO₂/Ar), affording a C₂H₄ Faradaic efficiency (FE_C2H4) of 57.5% with a partial current density (J_C2H4) of 110 mA cm^-2.