Direct borohydride-air fuel cells and batteries: toward non-precious metal catalysts and regenerative systems

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The sustainable and affordable generation of energy for the myriad of applications our modern society is employing, ranging in power requirement scale from micro-to mega-watts, demands a variety of systems with specific attributes for a certain class of applications. In the context of fuel cells, the direct borohydride (NaBH4) fuel cell (DBFC) is newer, having being first proposed in the 1960s and has started receiving significant attention only during the past decade. DBFC can overcome the challenges faced by much more intensely studied fuel cell systems (e.g. hydrogen, methanol) due to four factors: a) it is a hydrogen-rich liquid fuel stable in alkaline media, hence it simplifies the fuel delivery and storage, b) it has higher theoretical specific energy (9.3 Wh/g) compared to liquid fuels used in direct fuel cells (methanol, formic acid, ethanol), c) the inherent absence of carbon in the fuel removes the commonly encountered problems associated with catalyst poisoning by COad, and d) DBFC offers the realistic opportunity to eliminate completely the need for expensive Pt- based catalysts at both the anode and cathode. Dr. Gyenge's group is the only one in Canada studying DBFC. The research combines experimental work in applied electrocatalysis and electrochemical engineering with first-principles modelling of surface reactions which is carried out in collaboration with Prof. H. Kasai, Osaka University, Dept. of Applied Physics. Three critical areas are addressed: i) discovery of novel non-precious metal catalysts for the complete 8-electron oxidation of NaBH4 by studying osmium (which itself is five times cheaper than platinum) as a model, due to the unusal electrocatalytic activity and catalytic durability of osmium recently discovered by Dr. Gyenge's group, ii) electrodeposition of nanostructured MnO2 cathode for oxygen reduction in alkaline media, iii) investigation of the regeneration of NaBH4 by using bifunctional electrodes.