Vacancy-Enabled Mesoporous TiO₂ Modulated by Nickel Doping with Enhanced Photocatalytic Nitrogen Fixation Performance

Abstract

Photocatalysis provides a sustainable route to convert N 2 to NH 3 with the aid of a photogenerated electron. Beyond the typical issue in the photocatalytic field, NH 3 synthesis requires adsorption, activation, and hydrogenation of N 2 . In this report, Ni-doped TiO 2 (Ni-x-TiO 2 ) photocatalysts were fabricated by a simple sol−gel method to introduce the oxygen defects and Ni site on TiO 2 . The oxygen vacancy (Vo) enhances the adsorption of N 2 on the catalyst surface. The Ni doping induced a defect energy level below the conduction band, which prefers to accept the photogenerated electron. The electron captured by Vo tends to transfer to the adsorbed N 2 and activate N 2 . On the other hand, the Ni site is a typical H 2 production site. It provides enough H 2 for the hydrogenation of N 2 to form NH 3 . To sum up all of these advantages, Ni-doped TiO 2 displays a high NH 3 production rate of 46.80 μmol•g −1 •h −1 which is about 7 times higher than that of pure TiO 2 . This manuscript provides a potential method to design a highly efficient photocatalyst for the NH 3 synthesis.

A Review of MOFs and Their Composites‐Based Photocatalysts: Synthesis and Applications

“…In the past few decades, TiO 2 has been regarded as a promising photocatalyst for the photodegradation of organic pollutants. [ 339,340 ] However, the wide bandgap (≈3.2 eV) of TiO 2 greatly limits its photocatalytic performance. [ 341,342 ] Therefore, developing highly efficient photocatalysts for the remission of the environmental pollution has received remarkable attention.…”

Photocatalytic nitrogen reduction to ammonia: Insights into the role of defect engineering in photocatalysts

“…The nature of the interaction between the TMs and N2 primarily depends on the "acceptance-donation" of electrons, where the combination of empty and occupied d orbitals plays an indispensable role [297,298]. The TM center can accept the lone pair of electrons of N2 through the empty d orbital [299]. The backdonation of d electrons from the TMs to N2 can strengthen the N-TM bonds and also simultaneously weaken the N≡N bonds, facilitating effective N2 binding and activation [300].…”

Rational design of photocatalysts for ammonia production from water and nitrogen gas

“…Zaicheng Sun and coworkers prepared a nickel-doped TiO 2 (Ni-x-TiO 2 , where x = concentration of the Ni precursor controlled in the preparation step) photocatalyst using the sol-gel method [45] show Their optimized sample (Ni-0.8-TiO 2 ) exhibited an NH 3 production rate of 46.80 µmol•g −1 •h −1 under simulated solar light irradiation, which is seven times higher than the rate using pure reference TiO 2 . The Ni-0.8-TiO 2 sample extends the light absorption range to the visible light region with a bandgap energy of 2.92 eV, whereas pure TiO 2 absorbs only UV light with a bandgap energy of 3.2 eV as shown in Fig.…”