Biochar from pruning byproducts applied as electrode material in bioinspired metal-air batteries

Biochar is a heterogeneous, aromatic-rich organic material obtained from the thermal degradation of plant or animal biomass in the absence of oxygen, and could be exploited for a variety of uses, such as in soil amendment, as sorbent or feed additive. A convenient source of lignocellulosic materials for biochar production is represented by pruning residues, which would be otherwise discarded or burnt. In the project “Novel materials for bioinspired metal-airbatteries”, biochar from various pruning residues is valorised by exploiting it as electrode materials in electrochemical devices such as fuel cells, electrolyzes and metal-air batteries, which play a key role in many technological sectors.  In particular, wood-derived cathodes are tested in innovative electrochemical energy storage and conversion devices, namely aluminum-air batteries which, due to their high theoretical gravimetric capacity, are considered promising alternative to the lithium-ion batteries in terms of electrochemical performances, cost and eco-sustainability.

A key point of the project is the thorough elucidation of the original wood both from the chemical and morphological viewpoint. Indeed, the efficiency of the derived biochar-derived cathodes significantly depends on the molecular composition and anatomical structure of the used wood. Therefore, the amount and type of lignin of the selected lignocellulosic biomasses, together with the morphology of their internal wood structure will be assessed via different analytical tools, such as infrared spectrometry, nuclear magnetic resonance spectroscopy, as well as light, epifluorescent and scanning electron microscopy. Then, electrochemical polarization studies will allow evaluating the electrochemical performance of the prepared materials. Furthermore, the effect of different pyrolysis temperatures, as well as the addition of heteroatoms via biochar impregnation in nitrogen-rich solutions will be assessed in order to optimise the synthesis preparation of biochar-based cathodes. Finally, the electrochemical properties of biochar-based batteries will be correlated with the chemical and morphological features of biochar itself, as well as with that of the starting raw lignocellulosic pruning residues, so to unravel the chemical and anatomical properties underlying the observed electrochemical properties of biochar-derived batteries. Overall, the production of electrodes from made of biochar from pruning residues is expected to represent a novel and sustainable way to valorise precious lignocellulosic byproducts, which could in turn reduce our dependence from Li-based batteries, therefore, limiting the negative environmental consequences of their massive exploitation.