A series of Pd/TiO 2 catalysts were prepared by incipient wetness impregnation method followed by atmospheric discharge plasma treatment. In order to study the influences of plasma treatment on the catalysts, the samples were characterized by XRD, TPR, TPD, XPS and TEM technologies. It was found that the plasma treatment catalysts possessed a higher acetylene conversion and ethylene selectivity compared to those of the untreated sample. The enhanced performance of the plasma treated catalyst was mainly dependent on two main effects. On one hand, the treated catalyst possessed a higher metal Pd dispersion, which resulted in the easier activation of acetylene. On the other hand, the surface electron density of metal Pd on the treated catalyst got enhanced compared to that of untreated sample, because of the stronger interaction between TiO 2 support and metallic Pd, helping the more desorption of ethylene species from the surface of catalyst.
Controllably mounting foreign atoms on the surfaces of earth-abundant electrocatalysts strongly improve their surface electronic properties for optimizing the catalytic performance of surficial sites to an unusual level, and provides a good platform to gain deep insights into catalytic reactions . The present work describes, employing ultrafine W 2 C nanoislands (average size: 2.3 nm) monodispersed on the N, P dual-doped carbon frameworks as a model system, how to regulate the atomic phosphorous-mounting effect on the surfaces of W 2 C to derive an active and stable P-mounting W 2 C (WCP) catalyst for both acidic and alkaline hydrogen evolution reaction (HER). Since in situ phosphorus substitution into carbon sites of preformed W 2 C nanoislands gradually proceeds from surfaces to solids, so that using a proper amount of phosphorus sources can readily control the surface mounting level to avoid the mass P-doping into the bulk. By this way, the activity per active site of WCP catalyst with robust stability can be optimized to 0.07 and 0.56 H 2 s −1 at –200 mV overpotential in acid and base, respectively, which reach up to the several-fold of pure-phase W 2 C (0.01 and 0.05 H 2 s −1 ). Theoretical investigations suggest that compared with solid P doping, the P mounting on W 2 C surface can more remarkably enhance its metallicity and decrease the hydrogen release barrier. This finding disclosed a key correlation between surface foreign atom-mounting and catalytic activity , and suggested a logical extension to other earth-abundant catalysts for various catalytic reactions .
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