Photoelectrocatalytic nitrogen fixation with Vo-BiOBr/TiO2 heterostructured photoelectrode as photocatalyst

Photocatalytic or photoelectrocatalytic nitrogen fixation is considered as a very promising way to reduce energy requirements. Here, Vo-BiOBr/TiO2 nanocomposite photoelectrode was constructed by modifying TiO2 nanotube arrays with BiOBr nanosheets with oxygen vacancies (Vo) for photoelectrocatalytic nitrogen fixation. The oxygen vacancy promotes the adsorption and activation of N2 on the catalyst surface. The Lewis basicity of nitrogen is enhanced by transferring the photogenerated electrons on the conduction band of BiOBr to the π anti-bonding orbit of N2, which is more beneficial for the addition of protons. On the other hand, the heterojunction between TiO2 and Vo-BiOBr facilitates the separation of photogenerated carriers. The photogenerated holes on the valence band of TiO2 travelled to the counter electrode to produce oxygen at a negative potential, avoiding the further oxidation of NH3. Vo-BiOBr/TiO2 displays a high NH3 production rate of 25.08 μg h−1 cm−2 at −0.2 V which is 3.3 times higher than that of BiOBr/TiO2. The synergistic effect between TiO2 and Vo-BiOBr results in enhanced light absorption and higher photoelectrocatalytic efficiency for the N2 reduction reaction.