Tungsten trioxide (WO3), as a typical transition metal oxide, receives extensive attention because of its great potential applications in chromogenic, gas sensor , photocatalysis and batteries. Electrochromism is the phenomenon that a material can change its optical properties reversible by application of an electric field.

Nitrogen oxides (NOx) have become one of the main atmospheric pollutants with the increasing consumption of fossil fuels as well as the rapid growth of the automobile exhaust emissions. NOx causes serious environmental problems such as acid rain, photochemical smog, and ozone depletion.

Trivalent lanthanide ions (Ln3+) have caught a lot attention due to its applications as upconverting luminescent materials in biological analysis, counterfeit in printed documents, and back-lighting in liquid crystal displays.

Vehicle emissions by burning fossil fuels had produce serious air pollutions. Some major pollutants include itrogen oxides (NOx), sulfur dioxide (SO2) and volatile organic compounds (VOC). As the indoor environment has attracted more attentions, the indoor air purification device is becoming more popular in the market. 

Fossil fuels as the current major energy source has promoted many environmental issues due to the large-scale emission of CO2 and other pollutants. Issues brought by fossil fuels include global warming, climate change, and sea level rise. Solar energy as a clean energy source has caught great interest globally, and is belived to be a promising solution to climate change and fossil fuel depletion. Photoelectrochemical water splitting (PEC) is an effective solar conversion technology to store the energy in hydrogen gas (H2).

Nitrogen oxides (NOx) are produced from the emissions of stationary sources and automobiles. Direct emission of NOx into the atmosphere without purification will lead to photochemical smog, acid rain and even global warming. The selective catalytic reduction (SCR) of NO with NH3 is widely employed for reduction of NOx emissions from stationary sources like gas, oil and coal- fired power plants. The most common catalyst is vanadium well-dispersed on a titania support as V2O5-TiO2.

There are four main preparation methods of preparing tungsten copper: mixed-press sintering method, activation sintering method, infiltration method, and nano/ultrafine mixed powder sintering method.