Concurrent Oxidation-Reduction Reactions in a Single System Using a Low-Plasma Phenomenon: Excellent Catalytic Performance and Stability in the Hydrogenation Reaction.

The catalytic activity and stability of metal nanocatalysts toward agglomeration and detachment during their preparation on a support surface are major challenges in practical applications. Herein, we report a novel, one-step, synchronized electro-oxidation-reduction "bottom-up" approach for the preparation of small and highly stable Cu nanoparticles (NPs) supported on a porous inorganic (TiO 2 @SiO 2 ) coating with significant catalytic activity and stability. This unique embedded structure restrains the sintering of CuNPs on a porous TiO 2 @SiO 2 surface at a high temperature and exhibits a high reduction ratio (100% in 60 s) and no decay in activity even after 30 cycles (>98% conversion in 3 min). This occurs in a model reaction of 4-nitrophenol (4-NP) hydrogenation, far exceeding the performance of most common catalysts observed to date. More importantly, nitroarene, ketone/aldehydes, and organic dyes were reduced to the corresponding compounds with 100% conversion. Density functional theory (DFT) calculations of experimental model systems with six Cu, two Fe, and four Ag clusters anchored on the TiO 2 surface were conducted to verify the experimental observations. The experimental results and DFT calculations revealed that CuNPs not only favor the adsorption on the TiO 2 surface over those of Fe and AgNPs but also boost the adsorption energy and activity of 4-NP. This strategy has also been extended to the preparation of other single-atom catalysts (e.g., FeNPs-TiO 2 @SiO 2 and AgNPs-TiO 2 @SiO 2 ), which exhibit excellent catalytic performance.