Efficient Photocatalytic Decomposition of Aqueous NH3 Using a Simple Mesoporous Semiconductor Thin Film with External Quantum Efficiency of 35 (= 3.5 × 103%) Based on Total Incident UV Light

UV light-activated highly efficient photocata- lytic decomposition of ammonia to N2 in water was suc- cessfully achieved by using only a simple mesoporous TiO2 thin film coated on a transparent substrate with external quantum efficiency of 35 (= 3.5 9 10 3 %) based on the total incident UV light. The internal quantum effi- ciency exceeded 250 (= 2.5 9 10 4 %) in a large scale 22.2 L submodule meaning that ammonia was once acti- vated at TiO2 by UV light, the activated ammonia under- went more than 250 times oxidative decomposition by O2 probably via a kind of chain reaction mechanism.