Hydrogen Evolution at Conjugated Polymer Nanoparticle Electrodes

Abstract

Currently, there is a global effort being made to reduce greenhouse gas emissions through the implementation of renewable energies. An attractive alternative to fossil fuels is hydrogen, as it can be stored, transported and used as on demand as a liquid fuel while producing only water vapor as a by-product. The production of hydrogen can be attained through the photoelectrochemical splitting of water into hydrogen and oxygen, representing a sustainable, carbon neutral method of hydrogen generation. Our research focuses on the use of conjugated polymers, namely poly(3-hexylthiophene) (P3HT), as photocathode materials to convert solar energy into hydrogen. Using phenyl-C61-butryic acid methyl ester (PCBM) as an electron acceptor to effectively separate the photogenerated electron-hole pair within the semiconducting polymer, we can take advantage of these separated charges to perform electrochemical reactions at the polymer/electrolyte interface. This work investigates the preparation of nanostructured organic thin films from P3HT:PCBM nanoparticles and their characterization as photoelectrodes for photoelectrochemical hydrogen evolution. The morphology and optoelectronic properties of the nanostructured photocathodes are compared with conventional, solution-cast thin films of P3HT:PCBM. The nanostructured photoelectrodes provide increased surface area compared with solution-cast films, as well as greater control of the nanoscale morphology within each nanoparticle, leading to enhanced P3HT:PCBM phase segregation. The photo-assisted deposition of platinum nanoparticles as hydrogen evolution reaction (HER) catalysts onto the nanostructured P3HT:PCBM photocathodes facilitates the photoreduction of protons to H2.