Direct Glucose Fuel Cell: Carbon Support Effect on the Anode Nanocatalysts Efficiency
Authors: Lemoine Charly , Dubois Lionel , Napporn Teko W. , Servat Karine , Kokoh Kouakou Boniface 
Published: February 2020

Glucose is a promising fuel for new implantable electrochemical power sources due to its abundance in the human body. The selective oxidation of this sugar to gluconic acid requires an active and efficient catalyst surface. Platinum is the reference catalyst, but displays a fast deactivation due to the poisoning effect of strongly chemisorbed intermediates during glucose electro-oxidation1. On the other hand, gold is well known for its exceptional electrochemical activity and selectivity on aldehydes and hemiacetals conversion in a large pH window2. Combining these two metals as unique electrocatalyst for glucose oxidation, becomes a way to overcome poisoning issue. Furthermore, the nature of the support also plays an important role in the enhancement of the catalyst activity and stability. Recently, researches on graphene-like materials have shown the benefit of their utilization as support for electrocatalysts3. In the present work, gold and platinum monometallic and bimetallic nanoparticles have been synthesized on different carbon supports: amorphous carbon Vulcan XC 72R and reduced graphene oxide (rGO). Physicochemical and electrochemical characterizations show that i) Bromide Anion Exchange (BAE) synthesis method provides good anchorage and dispersion of the nanoparticles (particle mean size < 10 nm) on supports, ii) glucose electro-oxidation on gold monometallic catalysts starts at 0.3 V/RHE in alkaline media and before 0.1 V/RHE for platinum monometallic and bimetallic catalysts, iii) rGO supported platinum, and gold-platinum alloys (Au70Pt30
and Au50Pt50
) exhibit higher power density than the corresponding nanocatalysts supported on Vulcan when used as anode in an alkaline glucose/oxygen fuel cell (Figure 1). The electrochemical study in near-biological conditions confirms and even accentuates the differences between the supports in terms of efficiency, stability and compatibility.

The chromatographic and mass spectrometry analyses of the reactions products from the operation of this direct glucose fuel cell in alkaline medium demonstrate the presence of gluconate as a major product. Moreover, glucuronate considered as a high value added compound, has been clearly identified.

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Figure 1: Polarization and power density curves of different nanocatalysts used as anode in a glucose/oxygen fuel cell recorded in 0.1 mol L-1 KOH + 50 mmol L-1 glucose. All catalysts have a metal loading of 20 wt. % on carbon substrates. Pt/Vulcan is used as cathode catalyst.

Figure 1