Mott–Schottky Effect Leads to Alkyne Semihydrogenation over Pd-Nanocube@N-Doped Carbon

Abstract

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.

Simultaneously Realizing Rapid Electron Transfer and Mass Transport in Jellyfish‐Like Mott–Schottky Nanoreactors for Oxygen Reduction Reaction

“…Besides, the C 1s peaks in HPCM‐5 exhibits a slight shift to lower one compared to MPCM (Figure 2e). These results further indicated that electrons transfer from Fe to N doped graphitic C at the heterojunction interfaces 6,9a,10,18. Overall, the charge regulation by Mott–Schottky effect in HPCM‐5 effectively causes electrons redistribution, forming a fast electron transfer path and enhancing ORR performance, which will be further discussed latter.…”

“…N heteroatom‐doping in carbon can change the charge or spin distribution, which is beneficial to facilitate the O 2 adsorption and then improve the ORR performance 16. What is more, N doping could open the band gap of C by raising the conduction band bottom and lowering the valence band top 3h,9,10. The introduced N atoms are mainly pyridinic‐N (398.6 eV) and graphitic‐N (401.1 eV) in HPCM‐5, as revealed by the N 1s high‐resolution spectra (Figure 2d).…”

“…As shown in Figure a, a heterojunction model was established to describe interface interaction and accurate electron transfer between Fe and N‐doping graphitic carbon (NG). Electronically rich N atoms doping could open the band gap of graphitic carbon and change its work function, leading to lower valence‐band maximum ( E c ) and higher conduction‐band bottom ( E v ) 2c,3h,9,10. The Fermi level of metal Fe ( E Fa ) is within the band gap of NG and lower than Fermi level of NG ( E Fb ).…”

“…As a result, the dyadic catalysts have substantially improved the chemical reactivity, selectivity, and stability than their single counterpart. Thus, the concept of Mott–Schottky effect has been applied in many catalyst fields, such as photo‐catalytic,7 nitrogen fixation,8 organic reaction,5a,9 methanol dehydrogenation,10 oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) 6,11. However, to our knowledge, this advanced concept is rarely proposed in ORR electrochemistry.…”

Creation of Redox‐Active PdSx Nanoparticles Inside the Defect Pores of MOF UiO‐66 with Unique Semihydrogenation Catalytic Properties

“…Recently, it was found that the metal‐free frustrated Lewis pairs (FLPs) are also highly selective for alkene production . However, the high selectivity of alkenes, especially for the terminal alkenes, was resulted from strict control over the reaction time, because most of the reported semihydrogenation catalysts are also active in alkene hydrogenation reaction …”