Insights into defective TiO<sub>2</sub> in electrocatalytic N<sub>2</sub> reduction: combining theoretical and experimental studies

Yang, Li; Wu, Tongwei; Zhang, Rong; Zhou, Huang; Li, Xia; Shi, Xifeng; Zheng, Huaiji; Zhang, Yanning; Sun, Xuping

doi:10.1039/c8nr09564g

Cited by 137 publications

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“…In general, the Fe atom substitutes the five-coordinate Ti atom on the TiO 2 (101) surface and creation of oxygen vacancies (V) becomes more probable because of the charge compensation between the metal dopant and lattice defects. [26,53] Theunpaired electrons from V 1decorated Fe-TiO 2 present an open-shell singlet configuration (›fl), indicating the absence of Ti 3+ (Figure S16 a). This suggests that the Fe-doped TiO 2 (101) surface has more oxygen vacancies than that of pristine TiO 2 (101).…”

Section: Angewandte Chemiementioning

confidence: 99%

“…[1][2][3] To date,the dominant industrial route for NH 3 synthesis is the Haber-Bosch process using N 2 and H 2 as the feeding gases,b ut this process operates at high temperature and high pressure,a nd consumes al arge amount of energy while emitting CO 2 . [25] Recent studies have demonstrated that TiO 2 with oxygen defects has good electrocatalytic activity for the NRR, [26,27] and heteroatoms (B, [28] C, [29] V, [30] and Zr, [31] )a re effective dopants to enhance the NRR performances of TiO 2 catalysts. [5][6][7][8] Noble metals perform the NRR efficiently;however, their scarcity and high cost limits their application in large-scale N 2 reduction.…”

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confidence: 99%

“…[8][9][10][11] NRR research has thus shifted to development of noble-metal-free alternatives. [25] Recent studies have demonstrated that TiO 2 with oxygen defects has good electrocatalytic activity for the NRR, [26,27] and heteroatoms (B, [28] C, [29] V, [30] and Zr, [31] )a re effective dopants to enhance the NRR performances of TiO 2 catalysts. [25] Recent studies have demonstrated that TiO 2 with oxygen defects has good electrocatalytic activity for the NRR, [26,27] and heteroatoms (B, [28] C, [29] V, [30] and Zr, [31] )a re effective dopants to enhance the NRR performances of TiO 2 catalysts.…”

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Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Zhu

Xing

et al. 2019

Angewandte Chemie

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Titanium-based catalysts are needed to achieve electrocatalytic N 2 reduction to NH 3 with alarge NH 3 yield and ahigh Faradaic efficiency (FE). One of the cheapest and most abundant metals on earth, iron, is an effective dopant for greatly improving the nitrogen reduction reaction (NRR) performance of TiO 2 nanoparticles in ambient N 2 -to-NH 3 conversion. In 0.5 m LiClO 4 ,F e-doped TiO 2 catalyst attains ah igh FE of 25.6 %a nd al arge NH 3 yield of 25.47 mgh À1 mg cat À1 at À0.40 Vv ersus ar eversible hydrogen electrode.This performance compares favorably to those of all previously reported titanium-and iron-based NRR electrocatalysts in aqueous media. The catalytic mechanism is further probed with theoretical calculations.Asanessential activated nitrogen source,NH 3 is extensively used to manufacture dyes,p olymers,f ertilizers,a nd explosives,and it also serves as carbon-neutral energy carrier with high energy density. [1][2][3] To date,the dominant industrial route for NH 3 synthesis is the Haber-Bosch process using N 2 and H 2 as the feeding gases,b ut this process operates at high temperature and high pressure,a nd consumes al arge amount of energy while emitting CO 2 . [4] Electrochemical N 2 reduction offers an attractive alternative in an environmentally benign and sustainable manner,b ut the strong N N bond is fairly inert and thus difficult to break in ac hemical reaction, underlying the need for electrocatalysts with high activity in the nitrogen reduction reaction (NRR). [5][6][7][8] Noble metals perform the NRR efficiently;however, their scarcity and high cost limits their application in large-scale N 2 reduction. [8][9][10][11] NRR research has thus shifted to development of noble-metal-free alternatives. [12][13][14][15][16][17][18][19][20][21][22][23][24] TiO 2 is highly adaptable as asemiconductor catalyst because of its long-term thermodynamic stability,n atural abundance,a nd nontoxicity. [25] Recent studies have demonstrated that TiO 2 with oxygen defects has good electrocatalytic activity for the NRR, [26,27] and heteroatoms (B, [28] C, [29] V, [30] and Zr, [31] )a re effective dopants to enhance the NRR performances of TiO 2 catalysts. However,T i-based catalysts that simultaneously achieve al arge NH 3 yield with ah igh Faradaic efficiency (FE) are not available thus far.As one of the cheapest and most abundant metals on the earth, [32] Fe also exists in biological nitrogenases for natural N 2 fixation. [33] Fe compounds have been widely utilized as catalysts for artificial N 2 fixation in the Haber-Bosch [4] and electrochemical [34][35][36][37][38][39] processes.I ti st hus natural for us to explore use of Fe as ad opant for TiO 2 ,w hich has not been reported before.Herein, we report on our recent experimental results that Fe-doped TiO 2 is superior in performances for electrocatalytic N 2 reduction under ambient conditions.I n 0.5 m LiClO 4 ,t his catalyst achieves ah igh FE of 25.6 %a nd al arge NH 3 yield of 25.47 mgh À1 mg cat À1 at À0.40 Vv ersus ar eversible hydrogen electrode (...

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Section: Angewandte Chemiementioning

confidence: 99%

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confidence: 99%

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Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Zhu

Xing

et al. 2019

Angewandte Chemie

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“…The as-prepared TiO 2 , OV-TiO 2 -300, and OV-TiO 2 -400 nanostructures were employed as the electrocatalysts. [28,29] Furthermore, it is also an experimental evidence to verify the DFT calculation. Additionally, we also calculated the NH3 r on the basis of the area of the working electrode, which indicates that OV-TiO 2 -400 nanosheets exhibit the highest catalytic activity ( Figure S8, Supporting Information).…”

Section: Wwwadvmatinterfacesdementioning

confidence: 72%

Oxygen Vacancy–Enhanced Electrocatalytic Performances of TiO₂ Nanosheets toward N₂ Reduction Reaction

Fang

et al. 2019

Adv Materials Inter

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>10 MPa) and temperature (>300 °C). [2] This harsh condition is obviously energy consuming and accompanies a large amount of CO 2 output, bringing a serious global warming problem. Alternatively, multiple encouraging strategies, including photocatalysis, mimicking biological nitrogen, and electrocatalysis were gradually developed to realize artificial N 2 fixation at mild conditions. [3][4][5] Among them, N 2 electroreduction is considered as the most promising and environmentally benign way because the electricity utilized during the catalysis can be produced by some renewable sources, such as solar and wind energy. [6] It has been extensively reported that heterogenous catalysts play vital roles in breaking or lowing the energy barrier required in the rate-determining step in electroreduction from N 2 to NH 3 , [7] which is the key in further improving N 2 reduction reaction (NRR) performances. Up to now, although a number of electrocatalysts were investigated, including the metals, [8][9][10][11] the metal oxide or sulfide, [12][13][14] and metal-free compounds, [15][16][17] there are still many shortcomings. One concern is the low NH 3 generation rate ( NH3 r ) and the faradic efficiency (FE) values. It is therefore highly desirable to find effective strategies to further enhance the catalytic activity toward NRR of the heterogenous electrocatalysts.As a result of the high bonding energy of the NN triple bond (941 kJ mol −1 ), [18] N 2 is quite inert. To catalyze the NRR, it is thus indispensable to lower the energy barrier and activate the stable N 2 in an electrocatalytic reaction. Furthermore, the NH3 r and FE values will be significantly improved if the heterogenous electrocatalysts can offer sufficient active sites on their surface. From these perspectives, oxygen vacancies (OVs), one of the most important defects in semiconductor, are of particular interest to enhance the chemisorption and activation of inert N 2 molecules. [19] Furthermore, the OV formation can expose the coordinately unsaturated metal sites, resulting in further capturing and activating N 2 . In addition, the 2D nanosheets have drawn extensive attentions due to their impressive surface structure. [20,21] Generally, the surface area in 2D nanosheets allows a large number of exposed atoms to act as the active sites, which will undoubtedly improve the catalytic activity. The thin nanosheets can decrease the diffusion path, ensuring a rapid electron transport during electrocatalytic procedure. [22] It is therefore feasible that 2D OV-TiO 2 nanostructures will offer a favorable platform to facilitate the Electrocatalysts play vital roles in the enhancement of the catalytic performances of the reduction reaction from N 2 to NH 3 at ambient conditions. This study reports oxygen vacancy-contained TiO 2 nanosheets, which are explored as efficient electrocatalysts toward the N 2 reduction reaction (NRR). Oxygen vacancies are introduced and tuned by annealing the as-prepared TiO 2 nanostructures under H 2 /Ar atmosphere at different temperature...

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“…TiO 2 has attracted significant research interest, principally due to its abundance, nontoxicity, and high stability . Recent studies suggest that oxygen‐defected TiO 2 is effective for the NRR . Hybridization of TiO 2 with reduced graphene oxide is an effective strategy to enhance the NRR performance .…”

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Greatly Enhanced Electrocatalytic N₂ Reduction on TiO₂ via V Doping

et al. 2019

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As a sustainable alternative technology to the Haber–Bosch process, electrochemical N2 reduction offers the hope of directly converting N2 to NH3 at ambient conditions. However, its efficiency greatly depends on screening high‐active electrocatalysts for the N2 reduction reaction (NRR). Here, the recent experimental finding that V is an effective dopant to greatly improve the NRR performances of TiO2 toward ambient N2‐to‐NH3 fixation with excellent selectivity is reported. In 0.5 m anhydrous lithium perchlorate, V‐doped TiO2 nanorods attain a high Faradic efficiency of 15.3% and a large NH3 yield of 17.73 µg h−1 mgcat.−1 at −0.40 and −0.50 V versus reversible hydrogen electrode, respectively, rivaling the performances of most reported aqueous‐based NRR electrocatalysts. Density function theory (DFT) calculations are performed to gain further insight into the catalytic mechanism.

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Insights into defective TiO₂ in electrocatalytic N₂ reduction: combining theoretical and experimental studies

Abstract: Defective TiO2 acts as an effective electrocatalyst for N2-to-NH3 fixation with a yield of 1.24 × 10−10 mol s−1 cm−2 and FE of 9.17% at −0.15 V.

Cited by 137 publications

References 57 publications

Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Oxygen Vacancy–Enhanced Electrocatalytic Performances of TiO₂ Nanosheets toward N₂ Reduction Reaction

Greatly Enhanced Electrocatalytic N₂ Reduction on TiO₂ via V Doping

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Insights into defective TiO2 in electrocatalytic N2 reduction: combining theoretical and experimental studies

Abstract: Defective TiO2 acts as an effective electrocatalyst for N2-to-NH3 fixation with a yield of 1.24 × 10−10 mol s−1 cm−2 and FE of 9.17% at −0.15 V.

Cited by 137 publications

References 57 publications

Greatly Improving Electrochemical N2 Reduction over TiO2 Nanoparticles by Iron Doping

Greatly Improving Electrochemical N2 Reduction over TiO2 Nanoparticles by Iron Doping

Oxygen Vacancy–Enhanced Electrocatalytic Performances of TiO2 Nanosheets toward N2 Reduction Reaction

Greatly Enhanced Electrocatalytic N2 Reduction on TiO2 via V Doping

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Insights into defective TiO₂ in electrocatalytic N₂ reduction: combining theoretical and experimental studies

Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Oxygen Vacancy–Enhanced Electrocatalytic Performances of TiO₂ Nanosheets toward N₂ Reduction Reaction

Greatly Enhanced Electrocatalytic N₂ Reduction on TiO₂ via V Doping