Steering Carbon Hybridization State in Carbon-Based Metal-free Catalysts for Selective and Durable CO2 Electroreduction

Electrocatalytic CO2 reduction using metal-free catalysts offers a promising and cost-effective approach to global carbon neutrality. However, metal-free catalysts frequently suffer from unsatisfactory catalytic performances, especially a low current density and poor stability. Herein, by modulating the orbital hybridization state of carbon, we strategically design a regulable sp3 and sp2 hybrid carbon interface embedded with adjacent boron and nitrogen sites in carbon-based metal-free catalysts for CO2 electroreduction. Soft X-ray chemical imaging visually uncovers that the electronic structure and bonding configuration of the boron active site at the hybrid carbon interface are modulated by the neighboring nitrogen site and sp3 carbon. The concomitant electron density reconfiguration around the interface not only delivers optimum upshift of the boron p-band center, and accordingly the moderate valence-electron depletion, to stabilize the *OCHO intermediate favorable for HCOOH generation but also weakens the boron-carbon and boron-hydrogen hybridization of competing *COOH and *H species, respectively, to promote HCOOH selectivity over CO and H2. The designed electrocatalyst realizes a record-high formate partial current density of up to 50.8 mA cm-2 among metal-free catalysts in the H-cell and maintains a high Faradaic efficiency (>90%) over 108 h. This work elevates the carbon interface design with a tailored carbon hybridization state for efficient CO2 electroreduction.