Semiconductor metal oxides (SMOs) are highly potent gas sensors for gaseous detection in terms of screening of air eminence, low expenditure on synthesis and sensing property that can be modified. The semiconductor metal oxide gas sensor is considered the most capable gas-sensing device due to its high sensitivity, fast response, low cost, and small size.

Oxygen reduction reaction (ORR) has been widely studied for its applications in fuel cells. There is a growing demand for clean energy technologies such as fuel cells. Since the energy efficiency and battery voltage of electrochemical cells are limited by the slow kinetics of ORR.Currently, platinum dispersed on carbon (Pt/C) is the most active catalyst for ORR; however, in addition to its high cost, this metal also has problems with ORR overpotential and poor methanol tolerance. Supporting by transition metal oxides such as tungsten trioxide (WO3) and titanium dioxide (TiO2) to the Pt/C electrocatalyst provide not only active sites but also electronic and ionic conductivity.

Hydrogen (H2) is widely concerned as the most potential candidate due to its high energy density and environmentally friendly reaction process. Electrochemical water splitting is a promising hydrogen production technology because it does not contain greenhouse gases and is economical and efficient. As a key semi-reaction process, the hydrogen evolution reaction (HER) plays a decisive role in the efficiency and cost of hydrogen production through electrochemical water splitting.

The nitrogen oxides (NOx) produced by mobile and stationary sources are the main sources of photochemistry and smog acid rain. Ammonia selective catalytic reduction (SCR) is one of the most effective methods for removing NOx. It is widely used in power plants and other industrial environments.Due to its high oxygen storage capacity and excellent redox characteristics of conversion between Ce4+ and Ce3+, the application of cerium oxide-based oxides in the NH3-SCR reaction has attracted more and more attention. However, compared with vanadium catalysts, the SO2 tolerance is a great challenge for CeO2 SCR catalysts applied in stationary sources especially at low and mediate temperatures.

The reduction of fossil fuel sources, environmental pollution caused by engine fuel combustion, and concerns about energy supply have prompted researchers to look for renewable energy sources. Biodiesel has a high flash point (>130 °C), octane number and high combustion yield, as well as appropriate density and viscosity, excellent lubricants, and free sulfur and aromatic compounds. These characteristics have been applied to this engine without any modification and warm-up.

Nitrogen oxides (NOx) emitted by fossil fuel combustion are one of the main air pollutants, posing a serious threat to the ecological environment and human health. To cope with huge environmental pressure and strict emission targets, NH3 selective catalytic reduction of NOx (NH3-SCR) is still the mainstream NOx control technology.

Tungsten-copper (W-Cu) composite materials have comprehensive properties such as good thermal conductivity, electrical conductivity, low thermal expansion, non-magnetic, good performance under vacuum, and arc corrosion resistance, and are widely used in civil industry and aerospace fields. Therefore, they are often used as electrical contacts, especially in high voltage applications.

With the development of industrialization, nitrogen dioxide (NO2) in automobile exhaust and industrial emissions is a serious threat to human health and the ecological environment. 0.1 ppm or even less NO2 will cause significant health effect to human health. Therefore, the highly sensitive NO2 gas sensor has attracted widespread attention. In various gas sensors, metal oxide semiconductor-based sensors are widely applied in industrial, medical and other fields. Due to the presence of several oxidation states of W, tungsten oxide (WO3) is a common sensing material for NO2 semiconductor sensors.