Metal-organic framework-derived Co9S8 embedded in N, O and S-tridoped carbon nanomaterials as an efficient oxygen bifunctional electrocatalyst

Designing tailor-made metal-organic frameworks (MOFs) to synthesize target nanomaterials with extraordinary electrochemical oxygen catalytic activity is highly desirable. Here, we rationally designed a 2D Co-MOF [Co(BDC)(2)(SPDP)(2)(DMF)(H2O)] (H2BDC = 1,4-benzenedicarboxylic acid, SPDP = 4,4-(sulfonylbis(4,1-phenylene))dipyridine, DMF = N,N-dimethylformamide) as a single-source precursor through direct carbonization to afford an N, O and S-tridoped carbon matrix encapsulated with Co9S8 nanocomposites (Co9S8@TDC). By virtue of the intrinsic activity of Co9S8 nanoparticles (NPs) as well as the heteroatom-doped carbon shell, Co9S8@TDC possessed excellent electrocatalytic activities for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in alkaline solutions. In particular, Co9S8@TDC-900 displayed an overpotential of 330 mV (vs. RHE) at current density of 10 mA cm(-2) for OER and a half-wave potential of 0.78 V (vs. RHE) for ORR with the limiting current density of 5.45 mA cm(-2), rivalling the performances of RuO2 and Pt/C. As the proof of concept, Co9S8@TDC-900 was employed as a bifunctional oxygen catalyst for a rechargeable Zn-air battery, exhibiting a considerable open-circuit voltage (1.50 V) and impressive long-term charge/discharge stability (45 h at 5 mA cm(-2)). The straightforward strategy provides a facile method for the further exploration of non-noble metal electrochemical oxygen reaction catalysts.