Improved photocatalytic performance of TiO2/carbon photocatalysts: Role of carbon additive

A series of TiO2 - based photocatalysts have been prepared by the incorporation of 10 wt% of various carbon-based nanomaterials as modifying agents to titania. More specifically, commercial TiO2 P25 was modified through a wet impregnation approach with methanol with four different carbon nanostructures: single-walled carbon nanotubes (SWCNTs), partially reduced graphene oxide (prGO), graphite (GI), and graphitic carbon nitride (gCN). Characterization results (XPS and Raman) anticipate the occurrence of important interfacial phenomena, preferentially for samples TiO2/SWCNT and TiO2/prGO, with a binding energy displacement in the Ti 2p contribution of 1.35 eV and 1.54 eV, respectively. These findings could be associated with an improved electron-hole mobility at the carbon/oxide interface. Importantly, these two samples constitute the most promising photocatalysts for Rhodamine B (RhB) photodegradation, with nearly 100% conversion in less than 2 h. These promising results must be associated with intrinsic physicochemical changes at the formed heterojunction structure and the potential dual-role of the composites able to adsorb and degrade RhB simultaneously. Cyclability tests confirm the improved performance of the composites (e.g., TiO2/SWCNT, 100% degradation in 1 h) due to the combined adsorption/degradation ability, although the regeneration after several cycles is not complete due to partial blocking of the inner cavities in the carbon nanotubes by non-reacted RhB. Under these reaction conditions, Rhodamine-B xanthene dye degrades via the de-ethylation route.

Reversible Mg-Metal Batteries Enabled by a Ga-Rich Protective Layer through One-Step Interface Engineering

Practical applications of Mg-metal batteries (MMBs) have been plagued by a critical bottleneck─the formation of a native oxide layer on the Mg-metal interface─which inevitably limits the use of conventional nontoxic electrolytes. The major aim of this work was to propose a simple and effective way to reversibly operate MMBs in combination with Mg(TFSI)₂-diglyme electrolyte by forming a Ga-rich protective layer on the Mg metal (GPL@Mg). Mg metal was carefully reacted with a GaCl₃ solution to trigger a galvanic replacement reaction between Ga³⁺ and Mg, resulting in the layering of a stable and ion-conducting Ga-rich protective film while preventing the formation of a native insulating layer. Various characterization tools were applied to analyze GPL@Mg, and it was demonstrated to contain inorganic-rich compounds (MgCO₃, Mg(OH)₂, MgCl₂, Ga₂O₃, GaCl₃, and MgO) roughly in a double-layered structure. The artificial GPL on Mg was effective in greatly reducing the high polarization for Mg plating and stripping in diglyme-based electrolyte, and the stable cycling was maintained for over 200 h. The one-step process suggested in this work offers insights into exploring a cost-effective approach to cover the Mg-metal surface with an ion-conducting artificial layer, which will help to practically advance MMBs.

Reduction of 1 / f Noise in Single-Walled Carbon Nanotubes (SWCNTs) Using Gas Adsorption Technique

Single-walled carbon nanotube (SWCNT) plays a major role in electromagnetic absorption and shielding. Their applications as semiconductors make a breakthrough in communication by miniaturizing the communication devices. The main drawback of the SWCNT is found to $1/f$ noise. Because of this limitation, high attenuation at the low-frequency band cannot be achieved, limiting its application in terms of selectivity. The spectral density study shows that the noise’s amplitude is directly proportional to the temperature and inversely proportional to the number of carriers in the nanotube. The SWCNT is mainly synthesized using hydrocarbons which contains carbonaceous impurities. On the removal of impurities, more surface oxygen functional groups are formed. On the other hand, the diameter of the carbon nanotube is very small, increasing the resistance of carrier flow. In this research work, gas adsorption was used in SWCNT by treating the carbon nanotube using nitric acid. Isotherms determine porous size. The adsorbate-adsorbent interaction on carbon nanotube reduces the microporosity in the surface by treating with nitric acid. Therefore, the density of the surface increases and the CNT bundle separation will be reduced, increasing the carbon nanotube’s resistivity. This increase in resistivity reduces the excess carrier flow; therefore, the temperature will reduce the $1/f$ noise. The proposed system is cost-effective and has shown 11% improvement by reducing the noise amplitude by increasing carbon nanotube resistance. This proposed method has less complexity compared with existing models.

Using a Chloride-Free Magnesium Battery Electrolyte to Form a Robust Anode-Electrolyte Nanointerface

Magnesium bis(hexamethyldisilazide) (Mg(HMDS)₂)-based electrolytes are compelling candidates for rechargeable magnesium batteries due to their high compatibility with magnesium metal anode. However, the usual combination of Mg(HMDS)₂ with chloride salts limits their practical application due to severe corrosion of cell components and low anodic stability. Herein, we report for the first time, a chloride-free Mg(HMDS)₂-based electrolyte in 1,2-dimethoxyethane. By chemically controlling the moisture content using tetrabutylammonium borohydride as a moisture scavenger, the electrolyte demonstrates outstanding electrochemical performance in magnesium plating/stripping, with an average Coulombic efficiency of 98.3% over 150 cycles, and is noncorrosive to cell components. Surface analysis and depth profiling of the magnesium metal anode reveals the formation of a robust solid electrolyte interphase at the anode-electrolyte nanointerface, which allows magnesium plating/stripping to occur reversibly. The electrolyte also demonstrates good compatibility with a copper sulfide nanomaterial cathode, which exhibits a high initial discharge capacity of 261.5 mAh g^-1.