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Precisely regulating surface reconstruction of copper (Cu) chalcogenides‐based catalysts to promote the multicarbon (C2+)selectivity of the electrochemical CO2 reduction reaction (CO2RR) is hampered by the challenging control of the intractable anions and the optimal Cuδ+ reduction (0 < δ < 1). Herein, a porous carbon‐supported copper selenides electrocatalyst that can remarkably improve the C2‐product yield and especially unveil the time‐revolved electrochemical CO2RR reconstruction process to enable the high C2‐selectivity, most notably for ethanol is constructed. The Faradic efficiency (FE) of C2‐products achieved is as high as ≈85.2% with a partial current density of 229.5 mA cm−2. Operando infrared spectroscopy and density functional theory (DFT) calculations unravel that the surface Se vacancies (VSe) formation brings closer the neighboring Cu+ atoms and activates the Cu sites, thereby rendering efficient generation of the key intermediates (*CO and *CHO) and lowering the C–C coupling barrier for C2 production. The appearance of metallic Cu can shorten the next‐nearest Cu0–Cu+ distance for O atom to bridge in, leading to the preferential formation of *OC2H4 towards ethanol instead of C–O bond cleavage to form ethylene. This work opens the avenue of designing suitable local atomic structures catalysts to engage the intermediates for targeted CO2RR products. [ABSTRACT FROM AUTHOR]

Post‐treatment is a widely used strategy to reduce defects in perovskite films, but has been largely limited to the solution phase. Herein, the posttreatment tool kit and develop a universal amine salts (AIXI) vapor healing strategy by taking advantage of the penetrating power of vapor and the soft‐matter characteristics of halide perovskite is expanded. In a striking demonstration, the post‐treatment of pristine perovskite layers allows simultaneous filling of the MA+ and I– vacancies, passivation of both the cation and anion defects, and healing of the films to high order and high crystallinity required for high device performance, from the surface to the bulk and all the way down to the bottom. Experiments and DFT calculations revealed that charge extraction can be enhanced and non‐radiative recombination can be reduced by regulating the energy levels and reducing the trap states via the AIXI vapor healing. Moreover, the diffusing AIXI can reach the NiOx surface to obstruct the undesirable interfacial reactions and passivate the interface defects, further reducing the open‐circuit voltage (Voc) loss. The vapor healing strategy substantially reduces the trap density from 4.76 × 1015 to 1.04 × 1015 cm–3, and promots power conversion efficiency of the champion device from 17.92% to 20.48% with superior device consistency, Voc up to 1.114 V and the operational device stability. [ABSTRACT FROM AUTHOR]