Cu₂O nano-particles were prepared by the liquid-phase reduction method and the effect of the dispersant was studied. The microstructure, surface morphology and optical properties of Cu₂O nano-particles were characterized by X-ray diffractometer, X-ray photoelectron spectroscopy, nitrogen static adsorption, scanning electron microscope, particle size analysis, ultraviolet visible light spectrophotometer and photoluminescence spectrometer. The photocatalytic degradation of fluroxypyr using Cu₂O was studied by the response surface methodology, and the quadratic multinomial mathematical model was established. The results indicated that the Cu₂O crystal particles prepared using the dispersant of polyvinylpyrrolidone were of high purity with the preferential orientation of (111). The average particle size was 605.4 ± 124.8 nm, the specific surface area was 22.641 m²/g, the band gap was approximately 2.04 eV and the absorption edge was about 650 nm. R² of the established quadratic model was 0.9973 and had good fitness, indicating that the established model was reliable. The optimal degradation conditions were obtained as follows: the initial concentration of fluroxypyr was 11.17 mg/L, the pH of the solution was 12.0 and the H₂O₂ concentration was 15 mg/L. The degradation rate of fluroxypyr could reach 83.2% and the relative error was 1.20%. After nine times of recycling, more than 75% of fluroxypyr could be degraded.

A bifunctional electrocatalyst with high efficiency and low costs for overall water splitting is critical to achieving a green hydrogen economy and coping with the energy crisis. However, developing robust electrocatalysts still faces huge challenges, owing to unsatisfactory electron transfer and inherent activity. Herein, NiFe LDH/NiS₂/VS₂ heterojunctions have been designed as freestanding bifunctional electrocatalysts to split water, exhibiting enhanced electron transfer and abundant catalytic sites. The optimum NiFe LDH/NiS₂/VS₂ electrocatalyst exhibits a small overpotential of 380 mV at 10 mA cm⁻² for overall water splitting and superior electrocatalytic performance in both hydrogen and oxygen evolution reactions (HER/OER). Specifically, the electrocatalyst requires overpotentials of 76 and 286 mV at 10 mA cm⁻² for HER and OER, respectively, in alkaline electrolytes, which originate from the synergistic interaction among the facilitated electron transfer and increasingly exposed active sites due to the modulation of interfaces and construction of heterojunctions.

Cyclic voltammetry and chronoamperometry were used to study the deposition process at the initial stage of Cu₂O electrodeposition on indium tin oxide-coated glass. The current transient data and predicted values were analyzed by the instantaneous and progressive nucleation models under different electrolyte concentrations. The effects of the Cu₂O nucleation mechanism on microstructure and photoelectric properties of Cu₂O were investigated by X-ray photoelectron spectroscopy, X-ray diffractometry, scanning electron microscopy, ultraviolet visible spectrophotometry and fluorescence spectrophotometry. The results show that the electrochemical deposition process of Cu₂O is irreversible and controlled by diffusion, and the diffusion coefficient was calculated to be 2.2 × 10⁻⁶ cm²·s⁻¹. The nucleation mechanism of Cu₂O is related to the electrolyte concentration. When the concentrations of Cu(AC)₂ were 5 mM and 15 mM, the nucleation processes of Cu₂O were consistent with the progressive nucleation and instantaneous nucleation models, respectively. Under the instantaneous nucleation mechanism, the prepared Cu₂O displayed a uniform structure, composed of sword-shaped dendritic crystal. Compared to the progressive nucleation, the purity of the Cu₂O was higher, the bandgap narrower (2.006 eV), and the photoluminescence intensity higher. The Cu₂O had a high carrier density (4.9 × 10²² cm⁻³) and a low charge transfer resistance (127.27 KΩ·cm²). It exhibits superior photoelectric performance.