Weak-Field Electro-Flash Induced Asymmetric Catalytic Sites toward Efficient Solar Hydrogen Peroxide Production.

Borocarbonitride (BCN), in a mesoscopic asymmetric state, is regarded as a promising photocatalyst for artificial photosynthesis. However, BCN materials reported in the literature primarily consist of symmetric N-[B] units, which generate highly spatial coupled electron-hole pairs upon irradiation, thus kinetically suppressing the solar-to-chemical conversion efficiency. Here, we propose a facile and fast weak-field electro-flash strategy, with which structural symmetry breaking is introduced on key nitrogen sites. As-obtained double-substituted BCN (-BCN) possesses high-concentration asymmetric [B]-N-C coordination, which displays a highly separated electron-hole state and broad visible-light harvesting, as well as provides electron-rich N sites for O affinity. Thereby, -BCN delivers an apparent quantum yield of 7.6% at 400 nm and a solar-to-chemical conversion efficiency of 0.3% for selective 2e-reduction of O to HO, over 4-fold higher than that of the traditional calcined BCN analogue and superior to the metal-free CN-based photocatalysts reported so far. The weak-field electro-flash method and as-induced catalytic site symmetry-breaking methodologically provide a new method for the fast and low-cost fabrication of efficient nonmetallic catalysts toward solar-to-chemical conversions.