The information provided is given as reference. The gas molecules of Nitrogen dioxide (NO2) are not benefit to the human, plant, and animals. The gas can cause various problems, such as negative effect to lungs, smog rain, and is mainly fashioned from the burning of fossil fuels inside the combustion engines, alongside the other forms of NOx, such as NO and N2O.

Electrochromic (EC) materials have received distinguished attention because of their potential applications in smart windows, displays, and antiglare rearview mirrors. More interestingly, the electrochromic smart windows are considered being able to provide indoor comfort and reduce energy consumption in buildings because it could exhibit an ability to regulate the amount of sunlight entering the buildings. To achieve the excellent energy-saving effect, electrochromic smart windows should be able to adjust to near-infrared light along with visible light due to its broad range in sunlight.

Photocatalysis is a great technology to treat wastewater with environmental protection, more straightforward operation, high mineralization rate, and strong oxidation ability to efficiently remove the low concentration of organic pollutants in water.Tungsten trioxide (WO3) is a promising candidate for photocatalyst owing to its narrow energy gap (2.4–2.8 eV), high oxidation potential (+3.1–3.2 VNHE) of the valence band (VB), which is further meritorious for inducing the performance under visible light. WO3 is a widely studied metal oxide semiconductor for many cutting-edge applications such as photo/electrocatalysis, energy storage, smart window, antibacterial, anticancer agents, and pathogens control. Zinc tungstate (ZnWO4) has a wide band gap (about 3.8–5.7 eV) and possesses matched band structures with WO3. The introduction of ZnWO4 not only significantly promotes electron-hole separation but also broadens the absorption edge of WO3 and increases light absorption. Moreover, the addition of noble metal silver (Ag) can improve visible-light photocatalytic efficiency due to the increase of electron-transfer between semiconductor and noble metal.

Global energy demand, mainly based on unsustainable fossil fuels, has grown considerably during the last decades. Moreover, the emission of green house gases had caused environmental pollution and global warming.

Photocatalytic degradation has emerged as a promising technology for complete wastewater decontamination because of its organic and synthetic dormancy, essential limit, cost-viability, and long-haul security against chemical corrosion.

Metal oxide semiconductor (MOS) materials have been widely applied for gas sensing and environmental protection, because of their wide availability and high sensitivity to low ppm concentration of gases.

Tungsten carbide (WC) has several excellent properties, including high melting point (2600–2850 °C), great hardness, high fracture toughness, high electrical and thermal conductivities, which make it become a promising material in various fields. Considering these excellent properties, WC has been widely used as cemented tungsten carbide materials in the tool industry to produce cutting, mining tools, drilling tools and general wear parts.

Hydrogen fuel could play a key role in future sustainable energy systems as demand for energy is globally increasing. Moreover, an environment friendly energy resources are in urgent need to replace the current fossil fuel energy systems. Among the available energy sources, hydrogen possesses significantly high energy density compared to conventional fossil fuels and hence emerges as one of the ideal replacements to fossil fuels.

Tungsten (W) alloy are widely applied in many engineering applications including radiation shields, counterweight balance, electrical contacts, damping devices, and kinetic energy penetrators. The wide applications benefit from its high melting point, good thermal stability, high strength, and high radiation absorption capacity. However, tungsten alloy suffers from low temperature brittleness and unexpected growth characteristics in recrystallization.

Sustainable energy sources are crucial in the modern world, where conventional fossil fuels contribute towards an alarming percentage of hazardous pollutants in the environment. Hydrogen is a non-polluting fuel and a replenishable energy source, able enough to take the edge of an energy crisis. Noble metal platinum (Pt) has been proved to be the most effective electrocatalyst for hydrogen evolution reaction (HER). However, the high price of Pt limits its applications.