Sol-flame synthesis of cobalt-doped TiO₂ nanowires with enhanced electrocatalytic activity for oxygen evolution reaction

Abstract

Doping nanowires (NWs) is of crucial importance for a range of applications due to the unique properties arising from both impurities' incorporation and nanoscale dimensions. However, existing doping methods face the challenge of simultaneous control over the morphology, crystallinity, dopant distribution and concentration at the nanometer scale. Here, we present a controllable and reliable method, which combines versatile solution phase chemistry and rapid flame annealing process (sol-flame), to dope TiO2 NWs with cobalt (Co). The sol-flame doping method not only preserves the morphology and crystallinity of the TiO2 NWs, but also allows fine control over the Co dopant profile by varying the concentration of Co precursor solution. Characterizations of the TiO2:Co NWs show that Co dopants exhibit 2+ oxidation state and substitutionally occupy Ti sites in the TiO2 lattice. The Co dopant concentration significantly affects the oxygen evolution reaction (OER) activity of TiO2:Co NWs, and the TiO2:Co NWs with 12 at% of Co on the surface show the highest OER activity with a 0.76 V reduction of the overpotential with respect to undoped TiO2 NWs. This enhancement of OER activity for TiO2:Co NWs is attributed to both improved surface charge transfer kinetics and increased bulk conductivity.

Flame aerosol synthesis of nanostructured materials and functional devices: Processing, modeling, and diagnostics

“…Lithium propionate ethanol [47] Lithium tert-butoxide 113 tetrahydrofuran/toluene [51]; [52] toluene [52] xylene [51] Tributyl [54] chlorobenzene [53] xylene [ Magnesium tertbutoxide methanol/acetic acid [130] methanol acetic acid=1:1 [58]; [59]; [62] Al Alumatrane ethanol [34]- [38]; [47]; [74] ethanol/isopropanol [36] ethanol/isopropanol/1-butanol [36] ethanol/isopropanol/methanol [36] Ethanol:H 2 O = 97:3 [36] Tetrahydrofuran:ethanol = 9:1 [34] [60]; [61] ethanol [34]; [36] methanol/acetic acid mixture [130] Methanol:acetic acid=1:1 [58]; [59]; [62]; [72]; [73]; [347] o-xylene [101] s-butanol/xylene/methanol:acetic acid=1:1 [68] tetrahydrofuran / toluene [210] Aluminum butoxide [103][104][105][106][107][108][109][110] xylene [354] Aluminium isopropoxide…”

Resolving Hysteresis in Perovskite Solar Cells with Rapid Flame‐Processed Cobalt‐Doped TiO2

“…We applied the sol‐flame doping method to dope TiO 2 with Co; this method successfully introduced substitutional Co 2+ dopants into TiO 2 nanowires . The sol‐flame doping method combines high‐temperature annealing (1000 °C) with high heating/cooling rates, which enables a high concentration of metal dopants to be introduced without affecting the TiO 2 morphology and damaging fluorine‐doped tin oxide (FTO) glasses . The sol‐flame doping process for TiO 2 films is illustrated in Figure 1 a, and the details are described in the experimental section.…”

Fabrication of superior α-Fe2O3 nanorod photoanodes through ex-situ Sn-doping for solar water splitting

“…In most of the reports that use hydrothermal synthesis, dopants are incorporated into the hematite nanostructures during material synthesis (in-situ doping) [6,9,12,14,29]. In-situ doping is a simple process that uses a relatively low sintering temperature, allows for flexibility in the choice of dopants, and requires no additional doping steps [30]. However, changes in the morphology and crystallinity are observed for in-situ doped hematite photoanodes [6,15].…”