Breakdown and utilization
of cellulose are critical for the bioenergy
sector; however, current cellulose-to-energy conversion schemes often
consume large quantities of unrecoverable chemicals, or are expensive,
due to the need for enzymes or high temperatures. In this paper, we
demonstrate a new method for converting cellulose into soluble compounds
using a mixture of Fe
2+
and Fe
3+
as catalytic
centers for the breakdown, yielding Fe
3
O
4
nanoparticles
during the hydrothermal process. Iron precursors transformed more
than 61% of microcrystalline cellulose into solutes, with the composition
of the solute changing with the initial Fe
3+
concentration.
The primary products of the breakdown of cellulose were a range of
aldaric acids with different molecular weights. The nanoparticles
have concentration-dependent tuneable sizes between 6.7 and 15.8 nm
in diameter. The production of value-added nanomaterials at low temperatures
improves upon the economics of traditional cellulose-to-energy conversion
schemes with the precursor value increasing rather than deteriorating
over time.
Cyanobacteria grown in nitrogen-rich industrial wastewater showed increased productivity and higher methane yields when used as a feedstock for methanogenesis.
Indigo-carmine-mediated direct alkaline fuel cells have demonstrated superior power outputs over their non-mediated counterparts. Currently, the mechanism of mediation and stability of mediators are poorly understood. Upon exposure to highly alkaline solutions, we observed that the redox action of indigo carmine diminished, and significant currents were produced, indicating substantial degradation of the dye. The decomposition of indigo carmine at high pH and a poor thermal stability suggest that alternative mediators with low toxicity may be required to enable the widespread application of this device type.
Though direct carbohydrate fuel cells offer a highly efficient pathway from abundant, non-toxic sugars to electricity, currently their potential remains untapped due to a lack of knowledge of the impact of different cell geometries on their output power. In this work, simple modifications to the configuration of carbohydrate fuel cells are shown to significantly impact the performance of alkaline carbohydrate fuel cells. Increasing the density of a metal foam anode from 250 to 1000 mg/cm3 was found to increase power output by up to ~30%. These anode density changes also affected optimal fuel concentrations, which dropped from 1 M to 0.75 M. Decreasing the distance between electrodes from 20 mm to 6 mm resulted in improved maximum power outputs of ~35%. Identifying these new loss mechanisms in this device type provides a basis to optimise alkaline carbohydrate fuel cell performance and provide insights that help reconcile some of the disparities observed throughout the research space.
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