Si-doped and Si, N-codoped carbon nanomaterials exhibited much higher electrocatalytic activity and longer-term stability for the oxygen reduction reaction than non-doped carbon nanomaterials, due to the changes in net charges and the energy characteristics of the Si-containing carbon framework and the adsorption mode of oxygen.

The adsorption and dissociation of H(2) on the neutral and charged gold clusters Au(n) (m)(m=0,+/-1; n=1-6) is investigated using the density functional theory PW91 functional. H(2) interacts very weakly with Au(n) (-1), whereas the interaction with Au(n) (+1) is relatively strong. The binding energies on neutral clusters are between those on the cationic and anionic systems. The binding energy decreases monotonically with the size increase of the cationic clusters while it goes up first and then goes down on the neutral systems with the maximum value of 0.78 eV at Au(3). Au cations show no propensity for the dissociation barrier reduction and are thermodynamically unfavorable for the dissociation. For the first time we find that H(2) dissociation involves valley-ridge inflection points on some clusters. Our results indicate that H(2) dissociates facilely at low temperatures on both neutral and cationic Au(4) and Au(5). The phenomenon that H(2) dissociation was not observed experimentally is not due to the higher dissociation barrier and weak binding of H(2). We also show that the coordination number of the Au atom may not play a determining role in H(2) dissociation.

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We studied the adsorption of C(2)H(4) and CH(2)O on the gold clusters Au(n) (n = 1-5) in various adsorption modes using density functional theory PW91 functional. We found that the binding energies of pi-C(2)H(4) and pi and O-sigma modes of CH(2)O increase first and then decrease with the cluster size. Natural bonding orbital (NBO) analyses reveal that the donor-acceptor interaction plays an important role in these adsorption complexes and there is a nice linear relationship between the calculated binding energy and the stabilization energy estimated with second-order perturbation theory in the framework of NBO analysis. It is demonstrated that the bonding interaction between adsorbates and clusters follows the di-sigma > pi > O-sigma mode. However, due to adsorption induced structural deformation of adsorbates and clusters, the binding energies of different adsorption modes are comparable. It is shown that C(2)H(4) interacts more strongly with the clusters than CH(2)O does and that the previously assigned adsorption mode of C(2)H(4) on Au/MgO may not be the pi modes, but the C-sigma configuration.

Gold nanoparticles play a key role in catalytic processes. We investigated the kinetics of stepwise hydrogenation of acrolein on Au20 cluster model and compared with that on Au(110) surface. The rate-limiting step barrier of CC reduction is about 0.5 eV higher than that of CO hydrogenation on Au(110) surface. On Au20 nanoparticle, however, the energy barrier of the rate-determining step for CC hydrogenation turns out to be slightly lower than the value for the CO reduction. The selectivity difference on the two substrate models are attributed to different adsorption modes of acrolein: via the CC on Au20, compared to through both CC and CO on Au(110). The preference switch implies that the predicted selectivity of competitive hydrogenation depends on substrate model sensitively, and particles with more low-coordinated Au atoms than flat surfaces are favorable for CC hydrogenation, which is in agreement with experimental result.