Mechanistic study of reaction mechanism on ammonia photodecomposition over Ni/TiO2 photocatalysts

- Ni/TiO2 showed the highest activity among various metal-loaded photocatalysts for the decomposition of NH3 to N2 and H2.
- ESR measurements indicated that the NH2 radical was formed as an intermediate.
- It is possible that NH3 decomposition proceeded via the formation of NH2-NH2.

Photodecomposition of NH3 to H2 and N2 was carried out using metal-supported TiO2 (M/TiO2) photocatalysts in an aqueous NH3 solution under UV irradiation at room temperature. Ni/TiO2 photocatalysts indicated the highest yield of H2. The NH2 radical was formed as a dominant intermediate during NH3 decomposition, as confirmed by electron spin resonance measurements. Reaction pathways via NH2 radical formation were also investigated in detail by density functional theory. The results showed that H2 and the H2N-NH2 as intermediate were formed by the coupling of an NH2 radical and an NH3 molecule in the gas phase during the photodecomposition of NH3. We believe that our findings would be useful for further developing efficient catalytic systems.

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