Near-Infrared Active Tri-nanohybrid for Enhanced Energy Harvesting

Efficient energy harvesting through full solar spectrum utilization has been considered a promising solution to world energy and environmental issues. In this direction, lead sulphide (PbS) quantum dot (QD) based hybrid materials find greater application due to their near-infrared (NIR) active photo response. Slower charge injection and inefficient charge separation limit photoactive response of such NIR active low band gap semiconductor like PbS QDs. Moreover, constructing dual charge transfer pathways in a PbS QDs based nanocomposite through the formation of hybrids with suitable materials can be advantageous in suppressing the charge recombination. In this work, we have synthesized a nanocomposite after decorating the PbS-QDs with semiconducting TiO2 nanoparticles modified with multiwall carbon nanotubes (MWCNT) and thus forming the tri-hybrid (PbS-TiO2-MWCNT) nanocomposites. The enhanced photo-activities of the tri-hybrid, as compared to di-hybrids like PbS-TiO2, PbS-MWCNT were confirmed by the steady state, time-resolved photoluminescence (TRPL) measurements and reactive oxygen species (ROS) generation measurements. Higher ROS generation in the tri-hybrid has been correlated with a faster interfacial electron transfer due to the dual charge injection pathway of PbS QD to TiO2 and MWCNT. The enhanced activity of the trio-hybrid has also been analyzed from the first principal calculations in light of an efficient interfacial electron transfer as a result of the dual charge injection pathway. The photoelectrochemical water-spilling response of the photoanodes in terms of photocurrent density, electrochemical impedance, and Mott-Schottky measurements on PbS-TiO2 and PbS-TiO2-MWCNT photoanodes reveal that a combination of MWCNT and TiO2 exhibits an increase in electrical double layer capacitance, decrease in series resistance and enhancement of carrier density with NIR illumination at the heterojunction. Overall, all the dynamical studies at the interface of the trihybrid-based photoanodes demonstrate its potential of utilization as a futuristic NIR- active photoelectrochemical water-splitting material.