Decoding Dual-Functionality in N-doped Defective Carbon: Unveiling Active Sites for Bifunctional Oxygen Electrocatalysis.

Oxygen electrocatalysis plays a pivotal role in energy conversion and storage technologies. The precise identification of active sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for developing an efficient bifunctional electrocatalyst. However, this remains a challenging endeavor. Here, it is demonstrated that metal-free N-doped defective carbon material derived from triazene derivative exhibits excellent bifunctional activity, achieving a notable ΔE value of 0.72 V. Through comprehensive X-ray photoelectron spectroscopy and Raman spectroscopic analyses, the active sites responsible for oxygen electrocatalysis are elucidated, resolving a long-standing issue. Specifically, pyridinic-N sites are crucial for ORR, while graphitic-N are good for OER. A predictive model utilizing π-electron descriptors further aids in identifying these sites, with theoretical insights aligning with experimental results. Additionally, in situ ATR-FTIR spectroscopy provides clarity on reaction intermediates for both reactions. This research paves the way for developing metal-free, site-specific electrocatalysts for practical applications in energy technologies.