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

我们的现代社会正在采用的各种应用，从微型到兆瓦级的电力需求规模，都需要可持续和负担得起的能源发电，这就需要针对特定应用类别的各种具有特定属性的系统。在燃料电池的背景下，直接硼氢化物（NaBH4）燃料电池（DBFC）是较新的，在20世纪60年代首次提出，直到最近十年才开始受到重视。由于以下四个因素，DBFC可以克服更深入研究的燃料电池系统（例如氢，甲醇）所面临的挑战：a)它是一种富氢液体燃料，在碱性介质中稳定，因此它简化了燃料的输送和储存；b)与直接燃料电池中使用的液体燃料（甲醇、甲酸、乙醇）相比，它具有更高的理论比能（9.3 Wh/g）； c)燃料中固有的不含碳消除了与催化剂中毒相关的常见问题。d) DBFC提供了现实的机会，完全消除了在阳极和阴极对昂贵的铂基催化剂的需求。Gyenge博士的团队是加拿大唯一一个研究DBFC的团队。该研究与大阪大学应用物理系H. Kasai教授合作，将应用电催化和电化学工程的实验工作与表面反应的第一性原理建模结合起来。涉及三个关键领域：i)由于Gyenge博士的团队最近发现了不同寻常的电催化活性和催化耐久性，通过研究作为模型的钐（其本身比铂便宜五倍），发现了用于NaBH4完全8电子氧化的新型非贵金属催化剂；ii)在碱性介质中电沉积纳米结构MnO2阴极用于氧还原；iii)使用双功能电极研究NaBH4的再生。

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. The research program has significant breakthrough potential that could lead to the commercial viability of DBFC and it also provides excellent training for new researchers in the field of electrochemical power sources.