DFT Study of the BH4- Hydrolysis on Au(111) Surface

Revolutionary ZVI-Entrapped Sol-Gel Silica Matrices: Efficient Catalytic Reduction of High-Concentration Halo-Organic Compounds-Addressing Bromoacetic Acid Contamination in Industrial Wastewaters

The de-halogenation of highly concentrated halo-organic compounds using Zero Valent Iron entrapped in silica matrices as a catalyst was investigated. This study aimed to evaluate the effectiveness of the Zero Valent Iron-entrapped organically modified silica matrices in transforming highly concentrated hazardous halogenated compounds into environmentally benign materials in the presence of BH4-. The Zero Valent Iron-entrapped silica gel matrices were synthesized using the sol-gel method. The de-halogenation products were analyzed using high-performance liquid chromatography. The results suggest that the Zero Valent Iron-entrapped silica matrices are effective catalysts in the de-halogenation reaction of halo-organics by BH4- with 100% efficiency. The current work also highlights the complete de-bromination of harmful wastewater generated by the bromoacetic acid manufacturing industry using Zero Valent Iron-entrapped silica matrices. Therefore, Zero Valent Iron-entrapped silica matrices can be considered potential candidates for the catalytic removal of highly concentrated halo-organic compounds from contaminated water. This technology can play a crucial role in reducing the environmental impact of hazardous substances.

The Effectiveness of Silver and Gold in Catalytic Homogenous and Heterogenous Borohydride Hydrolysis - a DFT Study

Energy demands, and environmental aspects raised the need to study hydrogen-carrying material such as borohydride for the practical usage of hydrogen as a cleaner and more efficient fuel. A proper understanding of the hydrogen generation mechanism is a key requirement for the designing of efficient catalysts, as the non-catalytic hydrolysis of borohydride in non-acidic media is a slow process. The hydrolysis mechanism of borohydride varies considerably using homogeneous and heterogeneous catalysts. A comparison of the hydrolysis mechanism of borohydride using gold and silver as homogenous and heterogeneous catalysts is given in this review. Unexpectedly, with gold catalyst, Au+ or Au(111), only two steps of hydrolysis occur and BH(OH)2 is produced, while with silver catalyst, Ag+ or Ag(111), the hydrolysis can proceed to completion.

Hydrogen adsorption on various transition metal (111) surfaces in water: a DFT forecast

The hydrogen adsorption and hydrogen evolution at the M(111), (M = Ag, Au Cu, Pt, Pd, Ni & Co) surfaces of various transition metals in aqueous suspensions were studied computationally using the DFT methods. The hydrogens are adsorbed dissociatively on all surfaces except on Ag(111) and Au(111) surfaces. The results are validated by reported experimental and computational studies. Hydrogen atoms have large mobility on M(111) surfaces due to the small energy barriers for diffusion on the surface. The hydrogen evolution via the Tafel mechanism is considered at different surface coverage ratios of hydrogen atoms and is used as a descriptor for the hydrogen adsorption capacity on M(111) surfaces. All calculations are performed without considering how the hydrogen atoms are formed on the surface. The hydrogen adsorption energies decrease with the increase in the surface coverage of hydrogen atoms. The surface coverage for the H2 evolution depends on each M(111) surface. Among the considered M(111) surfaces, Au(111) has the least hydrogen adsorption capacity and Ni, Co and Pd have the highest. Furthermore, experiments proving that after the H2 evolution reaction (HER) on Au0-NPs, and Ag0-NPs surfaces some reducing capacity remains on the M0-NPs is presented.

The Competition between 4-Nitrophenol Reduction and BH4- Hydrolysis on Metal Nanoparticle Catalysts

Assessing competitive environmental catalytic reduction processes via NaBH4 is essential, as BH4- is both an energy carrier (as H2) and a reducing agent. A comprehensive catalytic study of the competition between the borohydride hydrolysis reaction (BHR, releasing H2) and 4-nitrophenol reduction via BH4- on M0- and M/M' (alloy)-nanoparticle catalysts is reported. The results reveal an inverse correlation between the catalytic efficiency for BH4- hydrolysis and 4-nitrophenol reduction, indicating that catalysts performing well in one process exhibit lower activity in the other. Plausible catalytic mechanisms are discussed, focusing on the impact of reaction products such as 4-aminophenol and borate on the rate and yield of BH4- hydrolysis. The investigated catalysts were Ag0, Au0, Pt0, and Ag/Pt-alloy nanoparticles synthesized without any added stabilizer. Notably, the observed rate constants for the 4-nitrophenol reduction on Ag0, Ag-Pt (9:1), and Au0 are significantly higher than the corresponding rate constants for BH4- hydrolysis, suggesting that most reductions do not proceed through surface-adsorbed hydrogen atoms, as observed for Pt0 nanoparticles. This research emphasizes the conflicting nature of BH4- hydrolysis and reduction processes, provides insights for designing improved catalysts for competitive reactions, and sheds light on the catalyst properties required for each specific process.