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Photocatalytic nitrogen reduction is the promising way for ammonia production, the question now is that the search of highly active and low active catalysts. Based on the first-principles calculation, single boron atom is anchored on the g-C$_2$N to form B/g-C$_2$N, the results show that B/g-C$_2$N can serve as a potential photocatalyst for N$_2$ fixation. The introduction of B atom to g-C$_2$N, the energy gap will reduce from 2.45 eV to 1.21 eV, and also show strong absorption in the visible light region. In addition, N$_2$ can be efficiently reduced on B/g-C$_2$N through the enzymatic mechanism with low onset potential of 0.07 V and rate-determing barrier of 0.50 eV. The "acceptance-donation" interaction between B/g-C$_2$N and N$_2$ plays a key role to active N$_2$, the BN$_2$ moiety of B/g-C$_2$N acts as active and transportation center. And the activity originates from the strong interaction between 1$\pi$1$\pi$* orbitals of N$_2$ and molecular orbitals of B/g-C$_2$N, the ionization of 1$\pi$ orbital and the filling of 1$\pi$* orbital can increase the N$\equiv$N bond length greatly, making the activation of N$_2$. Overall, this work demonstrates B/g-C$_2$N is a promising photocatalyst for N$_2$ fixation.

The TiC monolayer sheet, a new two-dimensional structure, is proposed as a promising hydrogen storage material because of its high specific surface area and the large number of exposed Ti ions on the surface. First principles calculations showed that both chemisorption and physisorption of H2 can take place on the TiC sheet surface, with adsorption energies of 0.36 and 0.09 eV per H2, respectively. For 1 and 1/4 monolayer (ML) coverages, the dissociation barriers of H2 on the TiC sheet surface were calculated to be 1.12 and 0.33 eV, respectively. Thus, as well as physisorption and chemisorption, there were dissociated H atoms on the TiC sheet surface. The maximum H2 storage capacity was calculated to be up to 7.69% (mass fraction). The capacities were 1.54%, 3.07%, and 3.07% for dissociated H atoms, and chemisorption and physisorption of H2, respectively. Considering only Kubas adsorption, the hydrogen storage capacity was 3.07% . The adsorption energy for H2 chemisorption on the TiC sheet surface only slightly changed at different coverages, which benefits the storage and release of H2.

Coherent transport through a quantum dot embedded in one arm of a double-slit-like Aharonov-Bohm (AB) ring is studied using the Green's function approach. We obtain experimental observations such as continuous phase shift along a single resonance peak and sharp inter-resonance phase drop. The AB oscillations of the differential conductance of the whole device are calculated by using the nonequilibrium Keldysh formalism. It is shown that the oscillating conductance has a continuous bias-voltage-dependent phase shift and is asymmetric in both linear and nonlinear response regimes.

Based on the density functional theory, we investigate negatively charged clusters , which show significant catalytic properties in the simultaneous removal of N2O and CO. We find that in these clusters, the platinum atom acts as the adsorption center for N2O, the gold and Pt atoms act as electron donors during the reaction, and the charge transfers from the bimetallic cluster to the N2O molecule. As the proportion of Au in the cluster increases, the d band center shifts down further away from the Fermi level, meanwhile more charge is transferred to the N2O molecule, resulting in weaker N–O bond strength. Therefore bimetallic cluster shows better catalytic properties than the other clusters, especially pure Pt4− and Au4− clusters. This means that there is a synergetic effect between the Pt and Au atoms in the negatively charged bimetallic clusters. Our results help to reveal the mechanism of bimetallic clusters as excellent catalysts.