Phase-Transition Engineering with Tuning of Defects in TiO₂ for Highly Efficient Electrochemical Nitrogen Reduction

Abstract

Titanium dioxide has recently received a lot of attention as a potential catalyst for the electrochemical nitrogen reduction reaction (NRR). However, the effect of surface reconstruction of titanium dioxide during the phase transition on electrocatalysis has attracted little attention. Here, we develop a facile one-pot phase-transition engineering strategy to implant defects in iron-doped titanium dioxide. Our engineering strategy shows advantages including a simple synthesis process, phasetransition efficiency, cost-effective materials, and scalability. The experimental results and density functional theory (DFT) calculations demonstrate that surface oxygen vacancies and doping Fe atoms play crucial roles as potential electrocatalytic sites for the NRR on Fe−TiO 2 catalysts, which enables efficient inhibition of the hydrogen evolution reaction (HER). A high NH 3 yield of 30.9 ± 0.4 μg h −1 mg cat.−1 and a Faradaic efficiency (FE) of 40.4 ± 1.1% at −0.4 V vs reversible hydrogen electrode are obtained for the NRR, outperforming most Ti-based catalysts reported previously. The formation and electrocatalytic NRR properties of Mn−TiO 2 , Co−TiO 2 , Ni−TiO 2 , and Cu−TiO 2 are also verified.

Interfacial Engineering Boosting the Activity and Stability of MIL-53(Fe) toward Electrocatalytic Nitrogen Reduction

“…26 Meanwhile, Fe is a traditional catalytic active center employed in the Haber−Bosch process and biological nitrogenase. 27,28 Furthermore, metal−organic frameworks (MOFs) have attracted great interest in the eNRR owing to their well-developed porosity, large surface area, custom-built architectures, and rich active sites. 29,30 Additionally, MOFs are widely employed as ideal substrates to obtain the highly active MOF-based catalysts, which have emerged as prospective electrocatalysts for eNRR.…”

“…Among various metal catalysts, the Fe element exhibits excellent performance for NN triple bond activation, owing to its abundant “d” orbital electrons and empty orbitals . Meanwhile, Fe is a traditional catalytic active center employed in the Haber–Bosch process and biological nitrogenase. , Furthermore, metal–organic frameworks (MOFs) have attracted great interest in the eNRR owing to their well-developed porosity, large surface area, custom-built architectures, and rich active sites. , Additionally, MOFs are widely employed as ideal substrates to obtain the highly active MOF-based catalysts, which have emerged as prospective electrocatalysts for eNRR. − Previous investigations have suggested that MOF-based catalysts can offer abundant active sites for electron transfer, thereby facilitating the NN cleavage . Despite its high activity, metal ions in the MOFs encounter critical electrochemical reduction and deactivation issues during the eNRR process because of the relatively weak coordination between metal ions and organic .…”