Phosphoric acid-etched boron nitride as a single-atom support for boosting CO₂ electroreduction at high current...

Designing adjustable and robust support materials remains a critical challenge for enhancing the industrial-level CO₂ electroreduction performance of single-atom catalysts. Herein, we report a defective and phosphate-modified boron nitride (BN) support via a facile phosphoric acid etching strategy to anchor single nickel atoms. The optimized electrocatalyst delivers an outstanding maximum CO faradaic efficiency of 97.6 ± 1.2% in an H-cell and a large CO partial current density of 148.6 ± 2.3 mA cm^-2 in a gas diffusion electrode-based flow cell and retains high CO selectivity during 87 h of stable operation. A variety of characterization studies including operando spectroscopy combined with theoretical calculations reveal that phosphoric acid etching redistributes the electronic structures of the interface as well as Ni centers, which significantly optimizes the *CO adsorption. Moreover, the surface phosphate species may play a critical role in stabilizing the key *COOH intermediate. This work not only provides a support material for achieving performance gain of transition metal single atoms, but also offers new insights into interfacial molecule-mediated CO₂ electrochemical conversion.