pH Dependence of Dihydroxyacetone Oxidation by Electrocatalytic\nViologen Self-Assembled Monolayers on Gold Electrodes

Carbohydrate fuel cells garner much\nresearch interest as the world’s\nfocus shifts from fossil fuels to renewable energy. Many catalyst\noptions are available for carbohydrate fuel cell development, including\nenzymes and microbes, various metal-based catalysts, and natural or\nsynthetic mediators. Research challenges include low power output,\nsystem fouling and poisoning, inefficient electron release, and complex\nmechanisms, with multiple pathways leading to low product selectivity.\nHere, we further investigate a novel approach to catalyze carbohydrate\noxidation using Au electrodes with viologen self-assembled monolayers\n(SAMs). SAM-mediated fuel cells have the potential to address the\nchallenges of other catalyst systems by protecting the electrode surface\nand controlling the local concentration and structure to increase\ncurrent generation. The effects of increasing pH on dihydroxyacetone\n(DHA) oxidation by three viologen SAMs on Au electrodes are presented.\nCurrent and power generated during DHA oxidation at varying pH were\nmeasured and compared to those of bare Au performance. Two of the\nSAMs produced more current and power than bare Au at elevated pH.\nThe SAM system produced more current and peak power per molecule than\nboth dilute and concentrated homogeneous viologen systems in the same\ncell setup. These results demonstrate the benefits and limitations\nof electrodes modified with redox-active groups for the production\nof electricity from simple sugars and other carbohydrate sources.\nThese results are encouraging for the development of new strategies\nfor electrical power generation from renewable resources.