Fe Ions-Doped TiO2 Aerogels as Catalysts of Oxygen Reduction Reactions in Alkaline Solutions

Abstract

Aerogels have interconnected networks and preeminent pore structures. When used as the catalysts for oxygen reduction reaction (ORR), they can facilitate the mass transfer and expose more active sites. Here, we synthesized the Fe-doped titanium oxide-based aerogels (TA/Fes) by the sol–gel method combined with thermal treatment. The specific surface areas of the TA/Fes ranged from 475 to 774 m2·g−1, and the pore volumes varied from 0.96 to 1.72 cm3·g−1. The doping effect of the Fe ions and the oxygen vacancies in anatase enhance the electrical conductivity, leading to the low Rct (313.3–828.2Ω). All samples showed excellent stability (2.0–4.5 mV) and 4e− pathway. The limiting current density of TA/Fe3 reached 5.34 mA·cm−2, which was comparable to that of commercial Pt/C. The preparation method is inspiring and the as-prepared aerogel catalysts have potential in promoting the scale of fuel cells.

General Approach to the Synthesis of Metal Hybrid Carbon/Titania Aerogel for the Oxygen Reduction Reaction

“…The results showed an increase of electron density for the Ti atom in CTA-M, which may be attributed to the formation of oxygen vacancies. 12,23 Although no XRDdetectable crystalline phase has been formed, this valence state existed in the system. This is due to the fact that these two peaks originated from oxygen vacancies in the anatase crystalline form, and the appearance of oxygen vacancies leads to the transformation of Ti 4+ to Ti 3+ to fit the electrostatic equilibrium in the system, thereby leading to a transformation in the electronic structure around Ti and the emergence of peaks.…”

“…In comparison to other samples, CTA-Fe-A showed better pore structure (high specific surface area and high pore volume), which enhanced the electrochemical catalytic performance, demonstrating the relationship between the catalytic performance and specific surface area and pore volume. The pore structure parameter of CTA/Sm-A is only compared to CTA-Fe-A, and its E onset and E 1/2 are improved in comparison to those of undoped samples, which are 0.82 and 0.66 V 12 . CTA-La-A and CTA-Zr-A have the worst pore structure, leading to the least E onset , E 1/2 , and J limit .…”

“…It can be observed that the Tafel slopes of CTA-Fe-A/N are superior to those of other metal-doped samples. 12,23 The number of transferred electrons (n) and hydrogen peroxide yield (HO 2 − ) are important performance indicators to evaluate the oxygen reduction electrocatalysts, as shown in Figure 12. The number of electrons transferred was 3.93 and 3.97 for CTA-Fe-A and CTA-Fe-N, corresponding to the HO 2 − yields of 3.6 and 1.39% when the potential was 0.6 V versus RHE.…”

“…Chu et al synthesized the Fe-doped titanium-oxide-based aerogels (TA/Fes) by the sol−gel method combined with thermal treatment. 12 The doping effect of the Fe ions and the oxygen vacancies in anatase enhance the electrical conductivity, leading to low R ct (313.3−828.2 Ω). All samples showed excellent stability (2.0−4.5 mV) and 4e − pathway.…”

Dye-sensitized solar cells based on highly catalytic CNTs/Ti3C2Tx MXenes composite counter electrode

“…[42][43][44][45][46] The measurement and analysis of R ct can provide an important reference for the elds of CE materials, electrochemical sensors, [47][48][49] and catalysts. 50,51 From the results, it can be found that the addition of Ti 3 C 2 T x has a signicant effect on the EIS of CEs. When the Ti 3 C 2 T x addition is 1.0 wt%, the C/T-1.0 wt% exhibits a value of R ct of only 6.64 U, which is much lower than the CNTs CE (14.39 U) and close to the performance of Pt CE (2.85 U).…”