We investigated the stability of reduced graphene oxide for oxygen density ranging from 6.25% to 50% with the density functional theory and found the most, the second most, and the third most stable oxygen configurations. The effect of relaxation of lattice on the electronic properties is found to be negligible for low O coverage and crucial for higher O coverage, respectively. The densities of states and the band gaps were calculated. The bandgap is found to be a non-monotonic function of oxygen density, with minima at O/C = 11.1% and 25%.

Cocatalysts for H2 production are often made from noble metals, which are expensive and rare. Cocatalysts made from cheap and abundant elements are therefore highly desirable for economically viable H2 production. Here, we demonstrate that amorphous transitional metal borides (TMBs)—made from abundant materials and costing less than 0.1% of the price of Pt cocatalysts—are effective substitutes for Pt-based cocatalysts and result in superior H2 production via water-splitting under visible light irradiation. Under visible-light driven photocatalytic water-splitting, using TMBs as cocatalysts for nanostructured NiCoB/CdS composites achieved an extraordinary H2 production of 144.8mmolh−1g−1, up to 36 times greater than that observed when using CdS alone. The apparent quantum efficiency was measured as 97.42% at 500nm, which is the highest value reported for CdS photocatalysts. The hydrogen atom adsorption energy (ΔE(H)) and hydrogen molecule adsorption energy (ΔE(H2)) of NiB, NiCoB and Pt have been calculated for the first time. Compared with Pt cocatalyst, amorphous TMBs cocatalysts more readily adsorb hydrogen protons and desorb molecular hydrogen during the photocatalytic process. Superior performance of TMBs as cocatalyst, much better than Pt, can be attributed to its powerful trapping electrons ability and highly adsorption of protons. These findings provide a straightforward and effective route to produce cheap and efficient cocatalysts for large-scale water splitting

Because of its novel physical properties, two-dimensional materials have attracted great attention. From first-principle calculations and vibration frequencies analysis, we predict a new family of two-dimensional materials based on the idea of octet stability: honeycomb lattices of pnictogens (N, P, As, Sb, Bi). The buckled structures of materials come from the sp³ hybridization. These materials have indirect band gap ranging from 0.43 eV to 3.7 eV. From the analysis of projected density of states, we argue that the s and p orbitals together are sufficient to describe the electronic structure under tight-binding model and the tight-binding parameters are obtained by fitting the band structures to first-principle results. Surprisingly large on-site spin-orbit coupling is found for all the pnictogen lattices except nitrogen. Investigation on the electronic structures of both zigzag and armchair nanoribbons reveals the possible existence of spin-polarized ferromagnetic edge states in some cases, which are rare in one-dimensional systems. These edge states and magnetism may exist under the condition of high vacuum and low temperature. This new family of materials would have promising applications in electronics, optics, sensors and solar cells.

Wide band gap CsPb₂Br₅ flake single crystals have been successfully obtained and demonstrated to have potential applications in deep-UV photodetection.