Catalytic Hydrogen Combustion

The intermittency associated with renewable energy sources can be mitigated through the use of an energy carrier that can be produced and stored during periods of energy abundance. Hydrogen (H2), as a carbon-free energy carrier, possesses the highest mass energy density relative to other fuels, making it a promising candidate. The chemical energy of H2 can be harnessed through oxidation via a highly exothermic reaction. Nonetheless, the broad flammability range of H2 in air, along with flame instability and elevated temperatures, presents challenges to conventional H2 combustion. Catalytic H2 combustion (CHC) involves the recombination of oxygen (O2) and H2 on the surface of a catalyst. With CHC, the temperature can be easily controlled, thereby minimizing the risks associated with flashbacks and the emissions of nitrogen oxides (NOx). CHC can be used directly for heat and power generation or to improve safety in H2-related applications by preventing the release of surplus H2 into the atmosphere at concentrations exceeding the lower flammability limit of H2 in air. Although the state-of-the-art catalysts for the CHC reaction are based on precious metals, ongoing research aims to discover alternative catalysts, understand the CHC mechanism over different catalysts, and develop new approaches to stabilize the H2 flame. This chapter reviews the efforts toward discovery and investigation of catalysts for the CHC reaction, the mechanism and kinetics involved, as well as applications of CHC for heat and power generation. Finally, the challenges associated with CHC and future research directions are discussed in the conclusion section.