Abstract
According to numerous previous reports, a Z-scheme with two photon absorbers is the most promising strategy to achieve artificial photosynthesis, but in addition to two efficient catalysts — one for oxygen evolution, the other for CO2 reduction — two different and complementary semiconducting sensitizers are required. Here we present the synthesis of two bipyridine-functionalized terthiophenes, which can be electropolymerized to give photoactive p-type semiconductors the capability to perform as photocathode in photoelectrochemical cells for water photosplitting or artificial photosynthesis. Indeed the bipyridine moiety in their structure allows the binding of transition metal carbonyl complexes employed in CO2 reduction, and their band-gap is suitable for the coupling with wide band-gap semiconductors, which have already found application as photoanodes. Finally, they are characterized by photogenerated charge carrier density between 1.1 and 1.4 × 1019 cm−3, with first-order recombination constant of 0.7–1.8 × 10−2 s−1. These figures are of the same order of magnitude of their inorganic counterparts and would therefore guarantee photoconductivity of the device and the activation of the organometallic catalysts with which they should be coupled to function as photocathodes for CO2 reduction.
Highlights
Energy availability at a low cost is a fundamental requisite to maintain the complex society to which we are accustomed
We report the synthesis of two bipyridine-functionalized terthiophene monomers and of their homopolymers and copolymers with thiophene, which we characterized at their photoelectrochemical properties with particular attention
We demonstrated the synthesis of two bipyridine-functionalized terthiophenes that can be electropolymerized giving p-type photoactive organic semiconductors, as witnessed by the open circuit potential (OCP)
Summary
Energy availability at a low cost is a fundamental requisite to maintain the complex society to which we are accustomed. Increasing efforts in recent decades have been dedicated to increase energy efficiency, to reduce the energy demand maintaining at least constant the quality of life and to improve the competitiveness of renewable sources such as solar, geothermal and wind power, with significant increase in cumulative capacity and market shares as results [2,3,4,5] In this perspective, artificial photosynthesis represents an important resource, because, converting solar power into chemicals can be complementary to battery technologies and photovoltaics in order to mitigate its intermittent nature and to allow its storage and transportation without needing a power grid. The electronic transport chains are usually simplified and involve a smaller number of intermediate steps Though simpler, this design is prone to recombination, which usually represents the main path for energy losses [11,12]
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