One of the biggest challenges of the 21th century is to consume environmentally friendly energy instead of the conventional non-renewable ones. Our largest available renewable energy source is sunlight, which might be harnessed using the gained knowledge in the field of photoelectrochemistry in the past 45 years. Photoelectrodes can help to store solar energy in the form of chemical energy, utilizing different photoelectrochemical (PEC) processes. This strategy, offers a viable avenue for direct H2 evolution and CO2 reduction to useful fuels. There are several requirements that a photoelectrode must fulfill: it has to be stable, insoluble in the test medium, resistant to photocorrosion; but in the meantime, it is expected to have a broad optical absorption, and to show good charge separation-, and transfer behavior. One single material, however, according to our current knowledge, cannot meet all these criteria. For this reason, the attention shifted to composite materials, which contain different components. Design and preparation of an effective composite photoelectrode material is a major undertaking – hence, it has become one of the main research projects in the field of photoelectrochemistry. In this study, we investigated the reasons behind the improved PEC performance of nanocarbon based photoelectrodes. For this purpose, various nanostructured electrodes were prepared, including carbon nanotube networks, spray-coated exfoliated graphene films, and 3D graphene foams. Variable amounts of p-Cu2O was loaded on their surface via a controlled, multiple-step electrochemical deposition protocol. We investigated the effects of various nanocarbon scaffolds, with primary focus on graphene. PEC measurements revealed better performance for the 2D graphene containing photoelectrodes, compared to the bare Cu2O films, if the geometrical area of the electrodes is considered. After taking into account the actual surface area of the nanostructured photoelectrodes, it was found that the 3D graphene based hybrids outperformed their counterparts. This could be rationalized by its interconnected structure, which facilitated effective charge separation and transport, leading to better harvesting of the generated photoelectrons. These structure-property relationships can be exploited in general for the rational design of hybrid photoelectrodes, to obtain potentially attractive candidates for PEC energy conversion schemes, such as water splitting or CO2 reduction.

Reasons behind the improved performance of cuprous oxide/nanocarbon photoelectrodes

254th National Meeting (2017)

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