In the past few decades, electrochromic devices have received great attention from researchers in related fields in the materials industry. Electrochromism is a reversible change in optical properties (such as absorbance and transmittance) of a material under low electric fields. Electrochromic devices have a wide range of applications, including reflective displays, smart windows, information displays, and electrochromic paper.

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.

Today, hydrogen is used in a variety of industrial applications. Initially, it was the basic material required in various chemical processes such as oil refining, the production of ammonia and methanol, and the synthesis of many polymers. In addition, hydrogen is also used in other industrial sectors, namely: glass and electronics production, metallurgy and food industry. Due to its characteristics, hydrogen is also considered to be one of the most important energy sources and can replace carbon-based fuels.

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.