Adjusting grain boundary within NiCo2O4rod arrays by phosphating reaction for efficient hydrogen production.

In this work, the density and electronic structures of the metal active sites in NiCo2O4nanorod arrays were concurrently tuned by controlling the sample's exposure time in a phosphorization process. The results showed that both the density and electronic structure of the active adsorption sites played a key role towards the catalytic activity for water splitting to produce hydrogen. The optimal catalyst exhibited 81 mV overpotential for hydrogen evolution reaction (HER) at 10 mA cm-2and 313 mV overpotential towards oxygen evolution reaction at 50 mA cm-2. The assembled electrode delivered a current density of 50 mA cm-2at 1.694 V in a fully functional water electrolyzer. The further results of theoretical density functional theory calculations revealed the doping of P elements lowered down the H adsorption energies involved in the water splitting process on the various active sites of P-NiCo2O4-10 catalyst, and thus enhanced its HER catalytic activities.

Nanoporous MoS2 Membrane for Water Desalination: A Molecular Dynamics Study.

Molybdenum disulfide (MoS2), a two-dimensional (2D) material, promises better desalination efficiency, benefiting from the small diffusion length. While the monolayer nanoporous MoS2 membrane has great potential in the reverse osmosis (RO) desalination membrane, multilayer MoS2 membranes are more feasible to synthesize and economical than the monolayer MoS2 membrane. Building on the monolayer MoS2 membrane knowledge, the effects of the multilayer MoS2 membrane in water desalination were explored, and the results showed that increasing the pore size from 3 to 6 Å resulted in higher permeability but with lower salt rejection. The salt rejection increases from 85% in a monolayer MoS2 membrane to about 98% in a trilayer MoS2 membrane. When averaged over all three types of membranes studied, the ions rejection follows the trend of trilayer > bilayer > monolayer. Besides, a narrow layer separation was found to play an important role in the successful rejection of salt ions in bilayer and trilayer membranes. This study aims to provide a collective understanding of this high permiselective MoS2 membrane's realization for water desalination, and the findings showed that the water permeability of the MoS2 monolayer membrane was in the order of magnitude greater than that of the conventional RO membrane and the nanoporous MoS2 membrane can have an important place in the purification of water.

Investigation on electrochemical performance of striped, ß12 and χ3 Borophene as anode materials for lithium-ion batteries.

By developing next-generation lithium-ion batteries (LIBS), demand for exploring novel anode materials with exclusive electrochemical features and ultra-high capacity is increasing. In the current research, first-principles theory, and density functional theory (DFT) calculations were conducted to extensively investigate and compare the capability of three different borophene nanolayers, including striped, ß12, and χ3 borophene, as a novel candidate for anode electrode in LIBs. We first predicted the most preferential Li atom adsorption sites on the three borophene structures. The predicted average formation energies for striped, ß12, and χ3 borophene were obtained 3.123, 3.184, and 3.216 eV, respectively. The positive value of formation energy exhibits the sufficient stability of the structures. Moreover, the negative adsorption energy proved that Li atom insertion on all borophene monolayers is thermodynamically favorable. In order to simulate the lithiation process, we gradually increased the concentration of Li atoms. We found that the fully lithiated striped, ß12 and χ3 borophenes could provide ultra-high specific capacities of 1700, 1983, and 1859 mAh/g, respectively. Structural analysis proved that the surface area expansion rate of the striped borophene in a fully lithiated state was 1%, which was lower than those of ß12 and χ3 borophene with 3.33% and 2.63%, respectively. The analyses of electronic properties confirmed that borophenes were inherently metallic and superior ion conductive agents, even after fully lithiated state. Ion diffusion was studied using Nudged elastic band method and the value of diffusion energy barrier ranged from 0.03 to 0.36 eV which was lower than other promising 2D anode materials. Furthermore, open-circuit voltage results demonstrated that the electronic potential of modeled borophenes was low enough to be in the acceptable range of under 1.2V. All these reports exhibited that borophene nanolayers with excellent specific capacity and superior conductivity were desired candidates for anode materials of next generation LIBs.