A “competitive occupancy”strategy toward Co-N4 single-atom catalysts embedded in 2D TiN/rGO sheets for high-efficient and stable aromatic nitroreduction
The single-atom catalysts (SACs) have been promising in catalytic fields, but the controllable synthesis of SACs with high stability remain challenging. Here, we show a robust strategy toward the highly-efficient and stable SACs based on “competitive occupancy” of two metal (M) species on graphite oxide (GO). The abundant M1 (Ti) species predominantly occupy more groups of GO, thus leaving a tiny of groups at the gaps of M1 species to combine with M2 (Co2+ etc.) species, and consequently, guaranteeing the formation of Co-N4 SACs embedded in 2D TiN/rGO sheets during the nitridation. Also, the TiN can act as a “spacer” to prevent Co-N4 from aggregation, thus improving the stability of the catalyst. The Co-N4/TiN-rGO exhibits outstanding catalytic performance for fast conversion of high-concentrated aromatic nitro compounds (0.3~2 mM) into amino compounds and excellent re-cycled ability, being at the forefront of reported catalysts. In contrast, the TiN/rGO has no obvious activity, and Co4N-rGO prepared without competition of Ti shows poor activity and stability, which indicate vital role of Co-N4 and TiN for remarkable catalytic ability of Co-N4/TiN-rGO. The reaction mechanism is also proposed based on the theoretical calculation. The strategy is indicative to design Ni (Fe, Cr, Cu)-based SACs .
- This article is part of the themed collection: Journal of Materials Chemistry A HOT Papers