Uniform CO2-enriched microenvironment enabled by sequentially functionalized hollow double-shell structure for maximal active site utilization in CO2 electroreduction

Sequentially functionalized hollow multishell architectures typically boost catalysis via enhanced site exposure and reactant enrichment; however, their potential to modulate intrinsic activity through spatiotemporal ordering remains elusive and underexplored. Here, we demonstrate that the sequentially functionalized double-shell architecture homogenizes mass transport to establish a uniform microenvironment, which synchronizes the electronic structures of active sites for equivalent excitation and maximized collective utilization, thereby enhancing catalytic activity and selectivity. A double-shell nanotube catalyst was developed, in which the pyridinic-N-doped defective carbon inner shell enables efficient CO 2 enrichment and supply within catalytic microenvironment, while the outer carbon shell hybridized with Ni single atoms and nanoparticles facilitates electrocatalytic CO 2 reduction. COMSOL simulations reveal that temporal-spatial ordering enhances both the magnitude and spatial uniformity of local CO 2 concentration at the active sites. This catalyst delivers enhanced CO 2 -to-CO activity and selectivity, achieving a CO partial current density of 496.5 mA cm –2 with Faradaic efficiency above 97.5% over 100–500 mA cm –2 in flow-cell, along with 145 h of stable operation at 100 mA cm −2 with FE CO > 94% in an MEA. The mechanistic analyses reveal that the uniform CO 2 -enriched microenvironment homogenizes and optimizes the electronic structure of all active sites, lowering the *COOH formation barrier and promoting *CO desorption to enhance catalytic performance. These findings reveal a previously unrecognized role of temporal‑spatial ordering, offering a powerful design principle for advanced catalysts.