Nanostructured Gallium Nitride Membrane at Wafer Scale for Photo(Electro)catalytic Polluted Water Remediation

Abstract

Photo(electro)catalysis methods have drawn significant attention for efficient, energy-saving, and environmental-friendly organic contaminant degradation in wastewater. However, conventional oxide-based powder photocatalysts are limited to UV-light absorption and are unfavorable in the subsequent post-separation process. In this paper, a large-area crystallinesemiconductor nitride membrane with a distinct nanoporous surface is fabricated, which can be scaled up to a full wafer and easily retrieved after photodegradation. The unique nanoporous surface enhances broadband light absorption, provides abundant reactive sites, and promotes the dye-molecule reaction with adsorbed hydroxyl radicals on the surface. The superior electric contact between the nickel bottom layer and nitride membrane facilitates swift charge carrier transportation. In laboratory tests, the nanostructure membrane can degrade 93% of the dye in 6 hours under illumination with a small applied bias (0.5 V vs. Ag/AgCl). Furthermore, a 2inch diameter wafer-scale membrane is deployed in a rooftop test under natural sunlight. The membrane operates stably for seven cycles (over 50 hours) with an outstanding dye degradation efficiency (>92%) and satisfied average total organic carbon removal rate (~50%) in each cycle. This demonstration thus opens the pathway toward the production of nanostructured semiconductor layers for large-scale and practical wastewater treatment using natural sunlight.

Incorporating Mesoporous Anatase TiO2 Spheres to Conductive Carbon Black Filled PVDF Membrane for Self-Cleaning Photo(electro)catalytic Filtration

“…The maximum absorption wavelength (λ max ) of MB is around 664 nm. The decolorization rates of MB were calculated using the following equation: η = A 0 − A A 0 × 100 % where η is the degradation efficiency and A 0 and A are the absorbance of the MB solution at initial and time t (min), respectively.…”

In Situ Oxidizing Commercial Alloy to Achieve Selective Solar Absorption with High-Temperature Stability

“…Based on the measured reflectance spectra, by increasing the heating temperature, the α ̅ solar increased from 0.713 at 700 °C to 0.848 at 900 °C and then dropped to 0.840 at 1000 °C. With the increasing oxidation temperature, the average size of the oxide increased, and the broad-sized nanostructure was beneficial for the extension of the solar absorption bandwidth, 24,25,32 and a slight drop in the α ̅ solar at 1000 °C can be attributed to the absorption peak away from the solar band although broadband solar absorption spectra can be achieved at a high heating temperature in Figure 3b. The ε ̅ IR increased from 0.094 at 700 °C to 0.223 at 1000 °C due to the increase in surface roughness and oxide thickness 24,33 (Figure 3b,c).…”

Robust Heteroepitaxial Growth of GaN Formulated on Porous TiN Buffer Layers

“…Group III nitride semiconductor materials have gained substantial attention due to their wide-range applications in power electronic devices, optoelectronics, piezoelectric-based surface acoustic wave devices, and various related technologies. These devices exhibit impressive properties, including high electron mobility, adjustable direct band gaps, a high breakdown voltage, and polarization benefits. − Especially, gallium nitride (GaN) has been extensively investigated and stands out due to exceptional chemical and physical stability, enabling GaN to be an ideal semiconductor for use in harsh conditions. , Despite the ongoing challenges in elucidating crystal growth mechanisms, GaN is arguably the most commercially important wide band-gap semiconductor (approximately 3.4 eV) since silicon (Si) and germanium (Ge); the prevalence of the GaN development in high-power electronics and solid-state lighting industries proves its importance. , Thus, many studies continue to explore the growth mechanism of GaN ,− while also developing complementary logic integrated circuits, broadband photodetectors, − and flexible and versatile electronics. , …”