External electric field induced hydrogen storage/release on calcium-decorated single-layer and bilayer silicene.

Hydrogen storage and release are two essential parameters that define the efficiency of a hydrogen storage medium. Herein, we investigate the effects of the external electric field F on the adsorption-desorption of H2 on a Ca-decorated silicene system (Ca-silicene) based on density functional theory calculations. Our study demonstrates that nine H2 molecules per Ca atom can be adsorbed and 6.4 wt% H2 can be adsorbed on Ca-silicene with an average binding energy of 0.19 eV per H2, while the appropriate F can be used to effectively enhance the hydrogen storage-release on the Ca-silicene system. The high synergetic effect may be attributed to the observation that F induces an enhancement of the charge transfer between H2 molecules and the Ca-silicene system. Thus, the Ca-silicene system together with the synergy of F can efficiently facilitate H2 adsorption-desorption, completing the whole hydrogen storage-release cycle.

Tuning electronic and magnetic properties of partially hydrogenated graphene by biaxial tensile strain: a computational study.

Using density functional theory calculations, we have investigated the effects of biaxial tensile strain on the electronic and magnetic properties of partially hydrogenated graphene (PHG) structures. Our study demonstrates that PHG configuration with hexagon vacancies is more energetically favorable than several other types of PHG configurations. In addition, an appropriate biaxial tensile strain can effectively tune the band gap and magnetism of the hydrogenated graphene. The band gap and magnetism of such configurations can be continuously increased when the magnitude of the biaxial tensile strain is increased. This fact that both the band gap and magnetism of partially hydrogenated graphene can be tuned by applying biaxial tensile strain provides a new pathway for the applications of graphene to electronics and photonics.

Revealing the active intermediates in the oxidation of formic acid on Au and Pt(111).

The mechanisms of formic acid (HCOOH) oxidation on Au(111) under gas-phase and electrochemical conditions was studied by using density functional theory and then compared with the analogous processes on Pt(111). Our results demonstrate that a mechanism involving a single intermediate molecule is preferred on both Au and Pt(111). Furthermore, under gas-phase conditions, HCOOH oxidation proceeds through the same mechanism (formate pathway) on Au and Pt(111), whereas under electrochemical conditions, it can take place through significantly different mechanisms (formate and/or direct pathways), depending on the applied electrode potential. Our calculations help to rationalize conflicting experimental explanations and are crucial for understanding the mechanism of this fundamental (electro-)catalytic process.