Global warming from extensive fossil fuel exploitation is the main reason for natural disasters worldwide. In the Net Zero Emission (NZE) pathway, H2 is a key role fuel. The main H2 production technology functioning, such as steam methane reforming (SMR) coal gasification (CG) and electrolysis, are reported together with the photocatalytic system one. A brief overview of the best materials discovered for photocatalytic application is then given and Quaternary Ammonium Cation (QUAT) Derived nano-materials (QDNs) are presented.
This work analyzes the possibility to use QDNs for photocatalytic applications as dyes’ degradation and H2 production. QDNs synthesis methodology, experimental procedure and QDNs characterization are reported. About photocatalytic dye degradation, it was found that, for each dye, at least one of the QDN tested was always able to completely (>95%) degrade the dye under 1 h. Additionally, it was discovered that the best material to use to degrade a dye is not always the same but it may change from dye to dye. The here tested QDNs always perform better than Titanium dioxide Evonik P25 (P25), used as reference, but when tested on sunset yellow. It was also seen that QDNs are active under dark condition. In particular crystal violet was degraded by QDN from TiB2 precursor of 69%, 87% and 94% after 0 min, 1 h and 7d in dark condition while the same values for methylene blue were 75%, 83% and 90%. Lastly, it was found that the solvent greatly affects degradation (water ensure the best results) while QDNs’ synthesis temperature, time and particle size are negligible parameters for long term degradation time (1 h) but not in the short term (5-10 min). Photo-catalytically H2 production results show that each QDN from TiC precursor (at different temperature) produced H2 with an apparent quantum yield (AQY) higher than 5% while P25 AQY was 1%. TCO3 (TiC QDN at 80°C) shows an incredible and constant 11.7% AQY over the 79 days in which it was tested. TCO2 (TiC-QDN at 50°C) shows an initial AQY of 3.4%. However, along the 182 days in which it was tested, AQY increased up to 12.6% of the last measurement thanks to a better re-dispersion of the powder in the H2O/MeOH mixture. The influence of the hole scavenger, of the stirring condition, of the catalyst concentration and of the gold doping was shown. Despite the enhanced AQY reached using gold, this drops quickly to low value (around 5%) making the material not stable.
To sum up, QDNs have shown to be an economical and environmental viable solution for the photocatalytic dyes’ degradation and H2 production.