Direct hydrazine fuel cells have been attracting much interest owing to their high theoretical standard equilibrium potential (1.56 V) and high-power density (5400 W h L−1). The electrocatalyst is the pivotal component for the fuel cells, and low-cost, earth-abundant catalysts with high activity and durability are highly desired. Grain boundaries bear many active sites for surface reactions (e.g. electrocatalysis and energy storage), and increasing the grain boundaries has become an important strategy to tune the number of surface active sites and the reaction kinetics. Herein, we show that a simple in-situ electrochemical tuning method can be used to turn Co(OH)x(CO3)0.5(2−x) crystals into interconnected ultrafine nanoparticles with enriched grain boundaries. The grain boundaries offer numerous unparalleled active sites for highly efficient electro-oxidation of hydrazine. To the best of our knowledge, this is the first report on the application of Co(OH)x(CO3)0.5(2−x) as an efficient catalyst for hydrazine electro-oxidation. The electrochemical evaluation was carried out in a typical three-electrode system. The electrochemically-tuned Co(OH)x(CO3)0.5(2−x) shows an onset potential (−1.12 V vs Ag/AgCl) 180 smaller than that of the pristine Co(OH)x(CO3)0.5(2−x), and delivers a high current density of 62.4 mA cm−2 at −0.90 V vs Ag/AgCl in 0.5 M N2H4 with 1.0 M KOH, which is 27 times higher than that of the pristine Co(OH)x(CO3)0.5(2−x). This work produces the most active non-metallic catalyst for hydrazine oxidation with catalytic activity comparable to the state-of-the-art catalysts. In addition, our electrochemical tuning method is applicable to other materials (e.g. Co3O4, Co(OH)2 and Ni(OH)2).

Electrochemically tuned cobalt hydroxide carbonate with abundant grain boundaries for highly efficient electro-oxidation of hydrazine

255th National Meeting (2018)

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