Boosting Selective Nitrate Electroreduction to Ammonium by Constructing Oxygen Vacancies in TiO₂

Abstract

Electrocatalytic nitrate reduction into recyclable ammonium under benign conditions is significant. However, the development of such a process has been retarded by the lack of efficient electrocatalysts for highly selective synthesis of ammonia from nitrate electroreduction. In this work, TiO 2 nanotubes with rich oxygen vacancies (TiO 2-x ) are reported to exhibit high Faradaic efficiency (85.0%) and selectivity (87.1%) toward the ammonium synthesis from nitrate electroreduction. 15 N isotope labeling experiments prove that ammonium originates from nitrate reduction. Both the 1 H nuclear magnetic resonance (NMR) spectra and colorimetric methods are performed to quantify ammonia. Online differential electrochemical mass spectrometry (DEMS) and density functional theory calculations reveal the function of oxygen vacancy in nitrate electroreduction, that is, the oxygen atom in nitrate fills in oxygen vacancies of TiO 2-x to weaken the N−O bonding and restrain the formation of byproducts, resulting in high Faradaic efficiency and ammonium selectivity. This strategy may open a paradigm for the development of rationally designed nanostructures as the electrocatalysts for selective nitrate electroreduction to ammonium.

Restoring the Nitrogen Cycle by Electrochemical Reduction of Nitrate: Progress and Prospects

“…[29] Density functional theory (DFT) calculations indicate that both nitrate and nitrite are twofold coordinated to the Cu (100) surface. [30] Twofold coordination is sterically favorable for the cleavage of the NO bond and had been employed in the first principles calculation for the mechanism of electrochemical reduction on catalysts. [30][31][32]…”

“…[ 30 ] Twofold coordination is sterically favorable for the cleavage of the NO bond and had been employed in the first principles calculation for the mechanism of electrochemical reduction on catalysts. [ 30–32 ]…”

Photodriven Disproportionation of Nitrogen and Its Change to Reductive Nitrogen Photofixation

“…[11,24,25] OVsi nT iO 2 are often created through the annealing of TiO 2 in an oxygenpoor environment or the reduction of TiO 2 under solvothermal conditions. [26][27][28] Thecreated OVstend to annihilate under oxidative conditions,w ith limited OV concentrations.T he introduction of alien metal ions in the TiO 2 lattice provides an effective way for the control of the OV concentration and stability. [29,30] In particular,s ubstitutional doping of Ti 4+ with Fe 3+ leads to the robust creation of OVs.…”

Preparation and application of one-dimensional nanomaterials derived from titanium carbide

“…催化活性. 例如, 西北大学郭晓辉团队 [30] 测试了一维 [44] (网络版彩图) (d) 循环稳定性测试前和测试后的极化曲线 [30] (网络版彩图) [89,90] 、二氧化碳还 原 [91,92] 、人工固氮 [93,94] 、甲醇电催化氧化 [95] 等电催化 领域也具有广阔的应用前景.…”