Cobalt Single Atoms in Hexagonal Boron Nitride Host for Efficient Electrochemical Nitrate Reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Stabilizing single transition-metal atoms in inert hexagonal boron nitride (hBN) is challenging due to a lack of anchoring sites.
• Developing efficient electrocatalysts for nitrate-to-ammonia electroreduction (NO3RR) is crucial for nitrogen conversion.

Purpose of the Study:

• To develop a novel strategy for anchoring single cobalt atoms within hBN nanosheets.
• To investigate the electrocatalytic performance of single cobalt atoms in hBN (Co1/hBN) for NO3RR.

Main Methods:

• In situ co-pyrolysis to synthesize Co1/hBN.
• Electrochemical testing of Co1/hBN and control catalysts (Co1/NG, carbon-supported Co atoms).
• EXAFS and DFT analyses to elucidate the coordination environment and reaction mechanism.

Main Results:

• Co1/hBN exhibited significantly higher NO3RR performance, with a sixfold increase in per-site turnover frequency compared to carbon-supported Co atoms.
• The catalyst demonstrated high Faradaic efficiency, yield rate, and a low Tafel slope.
• DFT calculations revealed that the polar hBN lattice facilitates nitrate adsorption and induces a flexible coordination environment (Co-N6 to distorted Co-N4) that lowers the energy barrier for NO3RR.

Conclusions:

• The in situ co-pyrolysis strategy effectively stabilizes single cobalt atoms in hBN.
• Host-induced coordination flexibility in hBN is a key factor for enhancing NO3RR kinetics.
• Co1/hBN represents a highly promising single-atom electrocatalyst for nitrogen-conversion reactions.