Influence of CVD parameters on Co‐TiO₂/CNT properties: A route to enhance energy harvesting from sunlight

Abstract

Carbon nanotubes (CNTs) have been employed to enhance the photoactivity of titanium dioxide (TiO 2 ). In this work, CNTs were deposited by chemical vapor deposition (CVD) onto the surface of anodized Co-TiO 2 nanotubes. The influence of CVD parameters (time and temperature) on the Co-TiO 2 /CNT structure and properties was investigated. We studied three synthesis times (10, 20, and 30 min) and two synthesis temperatures (700 and 800°C). The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD). The photocurrent performance of the electrodes was determined by linear voltammetry. The results showed the successful formation of Co-TiO 2 /CNT hybrid structures. The shortest synthesis time produced higher quality CNTs. The samples synthesized at 700 and 800°C for 10 min exhibited a current density of 1.13 mA.cm −2 and 7.84 mA.cm −2 , respectively, which is 9 and 65 times greater than the Co-TiO 2 sample. The synergistic effect of the CNT deposition and the crystalline phase composition significantly improved the photoresponse of TiO 2 .The proper choice of synthesis parameters allowed the control of the sample structure, leading to the production of electrodes with better light-harvesting performance.

Ultrafast growth of carbon nanotubes using microwave irradiation: characterization and its potential applications

“… Synthesis Methods Catalyst and substrate Carbon source Temp. (ºC) Time Flow rate of gases (ml/min) Product Quality References CVD Co/Al substrate CH 4 2100 15 min VACNT (d:9 um) [ 60 ] Ni/Co–TiB 2 C 2 H 2 900 C 2 H 2 ∼100 ml/min CNT-Co@TiB 2 [ 61 ] NiO/HZSM-5 zeolite PP 500–800 35 min Plastic feed rate 80 g/h, Hydrogen gas concentration 72.21 vol.% MWCNTs (15–25 nm) [ 62 ] Co–TiO 2 Hexane 700–800 10–30 min Hexane ∼150 ml/min MWCNTs (d: 15–30 nm) [ 63 ] Cu/CaCO 3 Pyrolysis gas 800 3 h Pyrolysis gas MWCNT [ 64 ] Arc- discharge Ni/Y Graphite rod 30V & 95A Ar ∼1.43 cm 3 /min; 39kPa MWCNT (d:24 nm and L: 690–1680 nm) [ 65 ] Fe Graphite rod 12kPa; 90A Fe2O3/CNT (d:10 nm) [ 66 ] Mixture of Carbon, paraffin & ZnO powder Graphite rod 20 s 500 Torr, 80A ZnO-CNT (3–10 nm) [ 67 ] Si/Ni Ethanol 30 s 4.5A Ni-filled/CNT (d:10 nm & L: 20–150 nm) ...…”

The effect of CaCO3 in the formation of carbon nanotubes via electrolysis of molten Li2CO3/CaCO3 mixtures

“…2,4,5,[14][15][16] Since the first synthesis of carbon nanotubes (CNTs) was elucidated by Iijima (1991), 17 the scientific community has been searching for methods that allow the production of these nanostructures in a controlled manner and with high quality. CNTs are currently synthesized by technologies such as plasma, 18 electric arc, 19 and chemical vapor deposition 20 techniques. However, the demand for these products is still limited, mainly due to the complexity and the cost involved in production, and consequently adding cost to the final product, they are currently valued at $85 000-$450 000 per ton.…”