The non-renewable fossil fuels are

The non-renewable fossil fuels are continuing to remain the dominant energy source in power plants and automobiles to satisfy the ever-growing energy demands. However, the combustion of fossil fuels mainly generates nitrogen oxide (NOx) pollutants (NO, NO2, and N2O and their derivatives) which can cause acid rain, photochemical smog, ozone depletion, and eutrophication problems [1–4]. Due to the negative impacts of NOx, the mitigation of NOx emissions is of paramount importance for environmental protection. Several technologies are available to reduce NOx emissions by using catalytic materials and among them, selective catalytic reduction of NOx with NH3 (NH3-SCR) has been widely applied due to its high NOx removal efficiency [5–7]. Usually, the flue gas temperature of the industrial process is as low as 300 ◦C and, thus, the SCR catalyst must be active in the low-temperature regime (100–300 ◦C). V2O5–WO3(MoO3)/TiO2 is the typical and efficient catalyst and has been commercialized for NH3-SCR technology for medium temperature process [8,9]. However, this catalyst has some intrinsic drawbacks such as narrow and high working temperature window (350–400 ◦C), and low N2 selectivity in the high-temperature range [3,10,11]. Therefore, many researchers continue to develop highly active catalysts for low-temperature NH3-SCR in a wide temperature window.