Cobalt tungstate (CoWO4) with monoclinic wolframite structure has been used in a wide range of potential applications including supercapacitors, photocatalysts, catalyst for oxygen evolution reaction (OER) and hydrogen production, microwave dielectric ceramics, photovoltaic electrochemical cells, among others. As electrochemical energy storage devices, batteries and supercapacitors have attracted significant attention due to their intrinsic characteristics of energy and power densities, cycling stabilities and charging-discharging rates.

A fabrication process of tungsten oxide (WO3) nanoplates with ammonium paratungstate has been performed, the product showed great photocatalytic activity due to the plate-like shape. Tungsten oxide (WO3) is a promising candidate for semiconductor gas sensors, electrochromic devices and photocatalysts. Structure and morphology of WO3 have obvious influences on its properties and applications. It has been reported that tungsten oxide with mixed structures exhibits poor optical properties, whereas the single-structure tungsten oxide, either hexagonal or cubic, exhibits noticeable absorption capacity.

As a hydrogen carrier for long-term sustainable energy supply, urea (CO(NH2)2) has been attracting increasing attention due to its stable, relatively non-toxic, non-flammable and renewable properties. Recently, the electrooxidation of urea has been used as an effective approach for hydrogen production as well as treatment of urea-rich wastewater.However, the current major challenge is to improve the catalytic activity and CO-tolerance of the catalyst.

Employing semiconductor powders as photocatalysis for the degradation of organic pollutants in water has received a lot attention in the last decade. Titanium dioxide (TiO2) inhibits amazing photocatalyst properties including high activity, chemical stability, and low cost. Nevertheless, the photocatalytic activity of TiO2 (with band gap of 3.2 eV and excited by photons with wavelengths under 387 nm) is still limited to irradiation by UV wavelengths, so that photocatalytic process does not occur effectively during the irradiation with solar light as only about 4% of the total radiation of the solar spectrum is in ultraviolet region. Thus, modification of TiO2 in the view to obtain a higher light absorption by shifting absorbance to the visible wavelengths has become the aim of many authors. One of the methods is the coupling of TiO2 with other semiconductors such as TiO2/CdS, TiO2/SnO2, TiO2/ZnO, and TiO2/WO3.

Photoelectrochemical (PEC) water-splitting technology is one of the most considerable technologies to synthesis H₂ gas as a clean energy. Titanium dioxide (TiO₂) has caught a lot attention as an effectual photoelectrode in PEC water-splitting for H₂ production owing to its unique and promising functional properties, such as high photocatalytic activity, long term photo-stability, superior oxidation ability, inertness to chemical environment, as well as low cost.

Tungsten oxide (WO3) is believed to be a remarkable and feasible photoactive material due to its stable physio-chemical characteristics under different reaction conditions. Furthermore, WO3 has a band gap energy around 2.6 eV. Nether less, bulk WO3 semiconductor, surface accumulation of photo generated charge carriers led to increase their recombination rate and eventually limiting the photocatalytic efficiency.

In recent years, ultrafine tungsten powders have gained attention owing to their excellent characteristics.  They have been added to hard metals and alloys with superior hardness and wear resistance. Ammonium paratungstate (APT), as important tungsten compound in tungsten industry, is usually utilized to produce metallic tungsten. However, the reduction process from APT to metallic tungsten several complex steps accompanied with different operational atmospheres and temperatures. Furthermore, the high-temperature methods usually failed to produce ultrafine tungsten particles.

Nitrogen oxides (NOx) are emitted from various industrial processes and transportation activities, especially coal–fired power plants. The SCR catalysts that are most used are those in which WO3 is added to VOx/TiO2 (anatase). These vanadium-based catalysts exhibit an excellent efficiency in a temperature range from 300 to 400 °C . However, these vanadium-based catalysts also suffer from several drawbacks, including the harmful effects of vanadium on the environment, the high likelihood of SO2 oxidizing to o SO3, a narrow operation temperature window (300–400 °C), and the formation of N2O at high temperatures.

In particular, ceria is a potential substitute for vanadium due to its oxygen storage capacity and high redox ability when shifting between Ce4+ and Ce3+. Production of tungsten doped CeO2/TiO2 has been achieved with ammonium paratungstate for SCR of NOx, The Ce/Ti with 10 wt.% ceria (10Ce/Ti) exhibited excellent activity.

The preparation method of the SCR catalyst is as following steps: Cerium (III) nitrate [10 wt.% Ce; Ce(NO3)3·6H2O by using ceria (5, 10, 20, and 50 wt.% Ce) and anatase-type TiO2 powder (DT51) had been used as precursors. A calculated amount of TiO2 was gradually added to the ceria solution while stirring. The mixture was agitated in a slurry state for more than 1 h; then the moisture was removed at 70 °C using a rotary vacuum evaporator (Eyela Co., N–N series); and the mixture was dried overnight at 110 °C. Finally, the mixture was calcined in air for 5 h at 500 °C.

The 10Cesingle bondW/Ti catalyst was prepared according to the following process. Cerium nitrate (10 wt.% Ce) and ammonium paratungstate (10 wt.% WO3) were mixed in distilled H2O. The calculated amount of the TiO2 support was impregnated in this solution by stirring for 1 h, and then the moisture was removed at 70 °C using a rotary vacuum evaporator. The mixture was then dried overnight at 110 °C, and was subsequently calcined in air for 5 h at 500 °C. W/10Ce/Ti was prepared through impregnation of 10Ce/Ti and ammonium paratungstate using the method described above.

To sum up, tungsten doped CeO2/TiO2 has been produced with ammonium paratungstate for SCR of NOx, The Ce/Ti with 10 wt.% ceria (10Ce/Ti) exhibited excellent activity. Thus, various metals were added to the 10Ce/Ti. The tungsten-doped 10Ce/Ti catalyst exhibited the highest activity. The highest Ce3+ ratio was observed in 10Ce/W/Ti at 0.3027, and the catalyst efficiency had a positive correlation with higher Ce3+ ratios. The SCR activity was found to increase as the Ce3+ ratio increased when tungsten was added to 10Ce/W/Ti. Thus, the addition of tungsten to Ce/Ti resulted in excellent NOx conversion and SO2 resistance.

WO3 is a popular and least bothered an n-type semiconductor with promising electrochemical properties, a high surface area, a small pore-size distribution, with several exciting chemical and physical properties, which have made it a appropriate material for various applications such as catalysts, gas sensors, and energy storage applications. However, the conventional synthesis methods have the drawbacks of high cost, time consuming, and high environmental pollution.

It is found that tantalum (Ta) and niobium (Nb) in concentrate of wolframite ((Fe,Mn)WO4) has been wasted: some of it goes to the insoluble residue after ammonium-leaching of the tungstic acid slurry; most of it goes to the solution of ammonium tungstate when (Fe,Mn)WO4 concentrate was digested by hydrochloric acid and the slurry of tungstic acid obtained was leached in ammonia. When the ammonium paratungstate (APT) was crystallized from the solution of ammonium tungstate, Ta and No were almost completely left in the mother liquor and their content reached up to 16 g/litre.