CuAs₂O₄: Design, Hydrothermal Synthesis, Crystal Structure, Photocatalytic Dye Degradation, Hydrogen Evolution Reaction, Knoevenagel Condensation Reaction, and Thermal Studies

Abstract

CuAs2O4 has been explored as a heterogeneous catalyst in the fields of photocatalysis, electrocatalysis, and solvent-free organic transformation reactions. The homogeneity has been successfully attained for the first time by designing a pH-assisted hydrothermal synthesis technique. Single-crystal X-ray diffraction studies reveal that no phase transition has been observed by lowering the temperature up to 103 K with no existence of satellite reflections. The crystal structure exhibits tetragonal symmetry with space group P42/mbc and consists of [CuO6] octahedra and [AsO3E] tetrahedra (E represents the stereochemically active lone pair). Structural investigation shows a cylindrical void inside the structure, which could lead to interesting physical and chemical properties. The photocatalytic dye degradation efficiency with methylene blue (MB) showed ∼100% degradation, though the degradation efficiency increased by 2-fold with the addition of 6% H2O2. The reusability of the catalyst up to the 10th cycle with ∼35% MB dye degradation has been established. It can exhibit HER activity with a low overpotential of 165 mV with respect to RHE to attain the current density of j = 10 mA cm–2. SEM and TEM revealed rod-shaped particles, which supported the large number of catalytic active sites. The structural consistency of the catalyst after photodegradation and HER studies is confirmed by the PXRD pattern. XPS confirms the oxidation state of Cu and As in the compound. The catalytic activity toward the Knoevenagel condensation reaction at moderate temperature under solvent-free condition is also studied. TG-DTA shows an endothermic minimum (T min) at 436 °C due to the mass loss of As2O3.

Constructing a P2W18O626–-Containing Hybrid Photocatalyst via Noncovalent Interactions for Enhanced H2 Production

“…Powder X-ray diffraction (PXRD) patterns were collected on a Rigaku Miniflex 600 diffractometer with Cu Kα radiation in the 2θ range of 3–60° with a step size of 0.02°. A Le Bail , fit was performed using the FULLPROF suite . 2θ zero shift and unit cell parameters were allowed to vary for the refinement.…”

Unraveling an Unusual Covalent C–Sb Bond Formation in a Co3Sb4CO6F6 Pseudo-superstructure

“…The presence of stereochemically active lone pair, cation and halide ions triggered to crystallize the [M-L-O-X] compound with interesting physical characteristics i.e., magnetism, surface properties, etc. − The [M-L-O-X] with soft halides (e.g., Cl/Br/I) possess a covalent metal-oxide network without bonded halide ions. The building blocks are generally interconnected through the oxide bridging resulting in layered structures, whereas the halide atoms reside in the van der Waals gap. − The transition metal oxyfluorides [M-L–O-F], on the other hand, possess different structural features as the fluoride atoms are directly attached with the metal centers. This structural imparity could be attributed to the size and electronegativity differences of the halides.…”