In situ grown Co9S8 nanocrystals in sulfur-doped carbon matrix for electrocatalytic oxidation of hydrazine

The development of effective and low-cost anode catalysts is a big challenge in the application of direct hydrazine fuel cell (DHFC). Herein, we report the in-situ grown Co9S8 nanocrystals into S-doped carbon matrix (Co9S8@S-C) as an efficient electrocatalyst for hydrazine oxidation reaction (HzOR). Co9S8 nanocrystals serve as the active site for electrocatalytic HzOR, and the conductive and porous S-doped carbon matrix not only promotes the charge and mass transfer, but also immobilizes and protects the Co9S8 nanocrystals from damage during HzOR. The optimal Co9S8@S-C-600 catalyst possesses a high Brunauer-Emmett-Teller (BET) specific surface area of 60.8 m2 g−1, and shows a current density (j) of 376 mA∙cm−2 for HzOR in alkaline medium at 0.3 V vs RHE, whose activity exceeds that of some previously reported electrocatalysts for HzOR. Furthermore, the activity retention rate of Co9S8@S-C-600 is 92.8% after 12 h HzOR test at a j value of greater than 300 mA∙cm−2, which is much better than that of Pt/C catalyst (15% activity retention). The excellent activity and durability of the Co9S8@S-C-600 catalyst are mainly attributed to the combined effect of highly active Co9S8 nanocrystals and the conductive and porous S-doped carbon matrixes, which makes Co9S8@S-C-600 as an effective non-noble metal electrocatalysts for HzOR.