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

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.