Confining Nickel Nanoparticles in Hierarchical Nitrogen-Doped Carbon Nanocages for Efficient Electrochemical CO₂ Reduction to CO

Electrochemical CO₂ reduction (CO₂RR) represents an attractive strategy for achieving carbon neutrality. Nevertheless, developing efficient and inexpensive catalysts is still challenging. Herein, we report a yolk-shell catalyst consisting of Ni nanoparticles (NPs) confined in hierarchical nitrogen-doped carbon nanocages (Ni@hNCNC) for efficient CO₂RR, which demonstrates high CO faradaic efficiency of 98% and impressive CO partial current density of 195 mA cm^-2 at -1.4 V (versus reversible hydrogen electrode) in neutral electrolyte and 352 mA cm^-2 at -1.1 V in alkaline electrolyte, outperforming the counterparts of Ni NPs supported on the outer surface of hNCNC (Ni/hNCNC) and confined in undoped hierarchical carbon nanocages. The combined experimental and theoretical studies reveal that the main active sites are the pyridinic N and Ni atoms at the interfaces of the Ni-hNCNC composite. The exceptional performance of Ni@hNCNC is attributed to the electronic interaction between N dopants and Ni NPs, the efficiently exposed interfacial active sites, as well as the confinement of hNCNC to keep a stable structure during CO₂RR. This study provides an efficient route to enhance the electrocatalytic CO₂-to-CO performance in neutral solution by confining a low-cost Ni catalyst in N-doped carbon nanocages.