Improving the selectivity and retaining the efficiency of catalysts are essential for industrial processes and remain a great challenge. Herein, we developed a facile route to synthesize Pd nanocubes (NCs) using Eosin Y as the photosensitizer under visible light. Subsequently, Pd NCs were uniformly loaded on N-doped carbon nanofibrous microspheres (NCMs) from carbonated chitin microspheres. This Pd NCs@NCM exhibited high reactivity and selectivity in alkyne semihydrogenation. For example, the hydrogenations of phenylacetylene to styrene and of 3-phenyl-2-propyn-1-ol to (Z)-cinnamyl alcohol were 12.9 and 18.3 times faster with Pd NCs@NCM than with Lindlar catalyst. According to the Mott–Schottky effect, loading of Pd NCs on N-doped carbon constructed a rectifying contact and decreased the electron density of Pd NCs. Density functional theory (DFT) calculations suggested that the high concentration of holes doped in Pd NCs weakened the interaction of alkenes on the Pd (100) facet and prevented further hydrogenation for a long time; this period of durable time is very helpful in chemical manufacturing. Thus, Pd NCs@NCM maintained both high reactivity and selectivity in comparison with surface-modified catalysts. This work provides an alternative strategy to design Mott–Schottky catalysts for selective hydrogenation reactions.
Jiashi Wang,Qinhong Wei,Qingxiang Ma,Zhongya Guo,Fangfang Qin,Zinfer R. Ismagilov,Wenzhong Shen
At present, the increasing consumption of fossil fuels as well as the expanding of more effective avenues to prepare carbon materials have inspired scholars' confidence to seek for alternative carbon sources. To address this issue, a N-doped graphene shell encapsulated metallic Co (Co@NGs) catalyst was fabricated using glucose and melamine as carbon source and nitrogen source via carbonization and employed for 5-hydroxylmethylfurfural (HMF) hydrogenation to produce 2,5-dimethylfuran (DMF) biofuel. Here, the prepared Co@NGs catalyst which possessed striking Mott-Schottky effect presented strong electronic interaction at the interface of surface metallic Co and doped N, leading to the electron transfer from metallic Co to doped N on carbon substrate. Experimental results indicated that the decreased electron density of metallic Co was more conductive to selective catalytic hydrogenation of HMF to form DMF. More importantly, the catalytic activity of the Mott-Schottky-type Co@NGs catalyst could be regulated by adjusting the nitrogen content. That is, the high nitrogen content increased the work function of Co@NGs and thus the enhanced rectifying response at the interface by which to enhance the catalytic performance. The best Co@NGs catalyst exhibited both high HMF conversion (close to 100 %) and DMF selectivity (94.7 %), much better than those of conventional N-doped carbon supported Co catalysts.
Jing Jiang,Wei Wei,Zhen Ren,Yang Luo,Xinzhi Wang,Ying Xu,Mingming Chang,Lunhong Ai
Developing efficient catalysts for the dehydrogenation of ammonia borane (AB) is important for the safe storage and controlled release of hydrogen, but it is a challenging task. In this study, we designed a robust Ru-Co 3 O 4 catalyst using the Mott-Schottky effect to induce favorable charge rearrangement. The self-created electron-rich Co 3 O 4 and electron-deficient Ru sites at heterointerfaces are indispensable for the activation of the B-H bond in NH 3 BH 3 and the O H bond in H 2 O, respectively. The synergistic electronic interaction between the electron-rich Co 3 O 4 and electron-deficient Ru sites at the heterointerfaces resulted in an optimal Ru-Co 3 O 4 heterostructure that exhibited outstanding catalytic activity for the hydrolysis of AB in the presence of NaOH. The heterostructure had an extremely high hydrogen generation rate (HGR) of 12238 mL min −1 g cat -1 and an expected high turnover frequency (TOF) of 755 mol H2 mol Ru -1 min −1 at 298 K. The activation energy needed for the hydrolysis was low (36.65 kJ mol −1 ). This study opens up a new avenue for the rational design of high-performance catalysts for AB dehydrogenation based on the Mott-Schottky effect.
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