The development of efficient, visible-light-responsive photocatalysts remains a critical challenge for the removal of persistent organic pollutants from wastewater. In this study, a graphitic carbon nitride–silver (g-C5N6-Ag) nanohybrid was synthesized via precipitation-induced assembly, enabling the uniform incorporation of Ag species into a carbon nitride framework with a carbon-to-nitrogen molar ratio of 1:1.22, as determined by elemental analysis. Structural and spectroscopic analyses confirmed that Ag incorporation preserves the intrinsic g-C5N6 structure while modifying its electronic properties, thereby enhancing light absorption and improving charge separation. The g-C5N6-Ag nanohybrid achieved over 99% methylene blue removal within 120 min under visible light, compared to 87% for pristine g-C5N6, with ∼97% removal within the first 10 min. Kinetic analysis referenced to the post-adsorption concentration revealed pseudo-first-order behavior, with a higher rate constant for g-C5N6 –Ag (0.0177 min⁻¹) than for pristine g-C5N6 (0.0119 min⁻¹) under visible light. Removal is strongly adsorption-assisted, with ∼95.6% of the dye taken up in the dark, after which irradiation degrades the surface-bound dye and regenerates the adsorption sites; efficiency was retained above 97% over five consecutive cycles. A terephthalic acid photoluminescence assay confirmed the generation of hydroxyl radicals, and scavenging experiments identified superoxide radicals and photogenerated holes as the principal contributors, with hydroxyl radicals playing a secondary role. This study demonstrates a simple strategy to improve the performance of carbon nitride-based photocatalysts for visible-light-driven wastewater treatment.
Copper-doped zinc vanadate nanocomposite (ZnV@Cu) was synthesized in a hydrothermal process with controlled Cu loading (1-5 mol%) and enhanced photocatalytic activity. XRD characterization indicates that phase-pure Zn3V2O8 was obtained with a general decrease in crystallite size from 32 nm (ZnV) to 18 nm (ZnV@Cu-3) along with increased strains and defect density. FTIR confirmed Zn–O–V and V–O–V bonding, while FESEM/TEM displayed a morphological transformation from rod-like crystallites (ZnV) to nanoscale agglomerates (ZnV@Cu-3). EDX and XPS confirmed uniform incorporation of 7at.% Cu with mixed Cu2+/Cu+ states. UV-vis absorption and Tauc’s plots exhibited progressive band gap narrowing from 3.44 eV (ZnV) to 2.24 eV (ZnV@Cu-3), consistent with enhanced visible-light absorption. PL and photocurrent studies corroborated the suppression of electron-hole recombination and improved charge separation upon Cu decoration. Photocatalytic hydrogen evolution studies under visible light demonstrated rates of 290.72, 429.13, 643.70, and 887.84 µmol g-1 h-1 for ZnV, ZnV@Cu-1, ZnV@Cu-2, and ZnV@Cu-3, respectively, with glycerol as the optimal sacrificial reagent. The best-performing ZnV@Cu-3 attained a maximum H2 evolution of 931.78 µmol g-1 h-1 at 363 K and retained 97% activity after five cycles. Simultaneously, ZnV@Cu-3 showed near-complete (99%) malachite green (MG) degradation within 150 min, with a pseudo-first-order rate constant of 0.031 min-1, nearly threefold higher than pristine ZnV. Scavenger tests indicated that hydroxyl radicals (•OH) and holes (h+) were the dominant reactive species. D2O isotopic labeling experiments proved that the real source of protons for photocatalytic H2 generation is water. The enhanced performance of ZnV@Cu-3 was explained by the synergetic effect of Cu-caused bandgap narrowing, defect-mediated charge transfer, and strong formation of the Cu-ZnV heterojunction. The results confirm that ZnV@Cu-3 is an effective, stable, and bifunctional photocatalyst for sustainable H2 generation and environmental remediation.
Aqueous zinc-ion batteries (AZIBs) are promising safer, eco-friendly alternatives to flammable lithium-ion batteries, yet suffer severe performance decay at high temperatures from zinc dendrites and electrolyte volatilization. In this work, a PAM/CMC dual-network crosslinked gel electrolyte (denoted as PCZ gel electrolyte) is constructed by coupling a physically crosslinked CMC network with a chemically crosslinked polyacrylamide network, forming a rigid–flexible interpenetrating framework. The carboxyl groups in CMC dynamically coordinate with hydrated Zn2+, regulating the solvation environment and reducing free water activity in the gel, thereby suppressing hydrogen evolution and corrosion reactions under high-temperature conditions. Meanwhile, the amide groups in PAM establish an extensive hydrogen-bonding network, which significantly enhances the mechanical robustness of the electrolyte. The resulting three-dimensional porous architecture further facilitates uniform Zn2+ transport and homogeneous zinc deposition. Notably, an anion-guided in situ film-forming strategy based on ZnSO4 is employed to regulate the gelation behavior. The moderate coordination strength of SO42- enables dynamic polymer–ion interactions while partially preserving the [Zn(H2O)6]2+ solvation structure and achieve high ionic conductivity and mechanical strength. Consequently, the Zn//Zn battery stably cycles for 600 h at 60 °C, and the Zn//MnO2 full battery retains 90% capacity after 1700 cycles under high temperature.
This study systematically investigated the effects of temperature (400 ∼ 510 °C), treatment time (4 ∼ 12 h), and N2:H2 ratio (1:1, 1:3, 1:5) on the microstructure, hardness, wear resistance, and corrosion resistance of 10CrNi3Mo gear steel. The nitrided specimens were characterized by scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Vickers microhardness testing, friction and wear testing, and electrochemical measurements. The results show that plasma nitriding produced a hardened surface layer comprising a compound layer and a nitrogen diffusion layer. As the temperature increased from 400 to 510 °C, the compound-layer thickness increases gradually up to 4.60 μm, while excessive temperatures caused non-uniform growth and substrate softening. The nitrided layer mainly consisted of Fe2-3N, Fe4N phases and nitrogen-expanded α phase. Higher temperatures and longer treatment times promote Fe4N formation, whereas increases N₂ concentration favored Fe2-3N precipitation. The surface hardness reached approximately 1000 HV0.05, and the effective hardened depth increases with temperature and treatment time. Plasma nitriding significantly improved the tribological and corrosion properties by changing the wear mechanism from adhesive to abrasive wear and reducing corrosion current density. Optimal wear resistance was achieved at 440 °C for 12 h with N2:H2 ratio of 1:3, giving a friction coefficient of 0.64 and wear rate of 1.414 × 10-10 kg/(N·m), while optimal corrosion resistance was obtained at 440 °C for 8 h with N2:H2 ratio of 1:3, where corrosion current density is as low as 0.410 μA·cm-2.
The weak optoelectronic characteristics of Nitrogen-rich graphitic carbon nitride (g-C3N5) hampered eminent photocatalytic activities; hence, we strived to rectify these limitations by using the cold plasma method. Herein, we employed two model inert gases (e.g., N2 and Ar) in the plasma to treat the pristine g-C3N5 (CN), enriching cyano-defects in the resultant nanoparticles (i.e., AxCN and NxCN). These cyano-rich samples had higher light-capturing ability, slower reunion rate of charge carriers, and lower charge transfer resistance than the CN. These merits led to ∼80% removal of Metronidazole (ME) using the A30CN photocatalyst at pH=9 under visible-light irradiation, which the degradation rate constant (k) of ME increased beyond 4.5-fold. Furthermore, the H2(g) evolution rate reached 1085.7 µmol g-1.h-1 (i.e., a 2.32-fold improvement) for the A30CN sample compared with the CN sample. Fortunately, the A30CN sample retained its photo-stability after successive cycles. Unsurprisingly, the growth rate of lentil and mung bean showed that an optimized system of H2O2/light/photocatalyst could effectively mitigate the negative impacts of ME. Overall, the cyano-rich g-C3N5 could be a suitable photocatalyst to enhance green energy production and environmental remediation.
