The formation of isocyanic acid (HNCO) by reaction of NO and CO with sources of hydrogen has been investigated along with its subsequent hydrolysis on oxides. High HNCO yields are possible with H₂ itself using Pt/SiO₂ and Pd/SiO₂ with Rh/SiO₂ less effective. The H₂ forms NH₃ and H₂O initially but they are recycled to HNCO as the temperature is increased. The NH₃+NO+CO reaction is equally as effective as a generator of HNCO. Oxides other than silica catalyse complete hydrolysis of HNCO to NH₃ and CO₂. The combination of HNCO formation from NH₃ and subsequent hydrolysis back to NH₃ allows the amplification of ammonia by a factor of 3 when using a combination of Pd/SiO₂ followed by CeO₂–SiO₂. Multiplication by 6 is possible with Pt/SiO₂ ahead of CeO₂–SiO₂ since additional HNCO is generated on Pt by the reaction of NO and CO with surface hydrogen derived through the water-gas shift reaction. The reaction of a H₂O/NO/CO mixture over a Pt/Al₂O₃ catalyst forms NH₃ with >80% yield in this way.