Preparation And Performance Of Cobalt Phthalocyanine-Based Cathode Catalysts

Fuel cells have been considered as one of the most effective ways of hydrogen energy with many advantages such as high energy efficiency, environmental protection, and power density so on. Up to date, Pt-based catalysts are still the most used ones for the fuel cell, but high cost and rare reserves of noble metals Pt has seriously limited the large-scale commercialization. Therefore, it is of interest and importance to explore non-precious metal electrocatalysts with low cost and high performance for development of fuel cells.Metal phthalocyanine compounds are promising catalyst precursor for the ORR because of M-N4 units in the structure. Layered double hydroxides (LDHs) is one kind of anionic lamellar compounds with adjustable chemical compositions and tunable charge density in the host sheet, and changeable guest anions in the interlayer regions. LDHs have been widely used as absorption materials, functional additives for polymers, and catalysts or catalysts precursors. Therefore, it is possible to obtain bifunctional non-precious metal electrocatalysts based on the absorption property and intercalation ability of the LDH with metal phthalocyanine compounds.In this work, NiFe-LDH was prepared by nucleation/crystallization separation method developed in the laboratory, and then the NiFe-LDH was used to absorb CoPcTs and intercalate with CoPcTs to produce CoPcTs/Ni2Fe-LDH and Ni2Fe-CoPcTs-LDH precursors, respectively. The precursors were calcined under inert atmosphere at optimized temperature to obtain Co/CoNx/NiFe2O4/C bifunctional electrocatalytic catalysts. Furthermore, various characterization techniques such as XRD, TEM, and RDE so on were applied to analyze crystal structure, morphology, electrocatalytic performance.(1) A series of CoPcTs/Ni2Fe-LDH precusors with different absorping content of CoPcTs were prepared by adjusting absorption time and then were calcined to produce Co/CoNx/NiFe2O4/C catalysts. Among the investigated samples, the best one was Co/CoNx/NiFe2O4/C when the absorping content was 120 mg·g-1:an onset potential of 0.86 V vs. RHE, a half-wave potential of 0.72 V vs. RHE, and current density of -5.20 mA cm-2 at 0.50 V vs. RHE at a rotating speed of 2500 rpm and the 4e pathway for ORR, and a low overpotential (380 mV) at a current density of 10·mA cm-2 for OER. The ?E (oxygen electrode activity parameter for evaluating the overall electrocatalytic activity and reversibility of a bifunctional electrocatalyst) value for CoNx/NiFe2O4-120 is 0.86 V.(2) A series of Ni2Fe-CoPcTs-LDH precursors were prepared by intercalation of CoPcTs into Ni2Fe-SDS-LDH and then were calcined to obtain Co/CoNx/NiFe2O4/C catalysts. When the intercalated CoPcTs was 141 mg·g-1, the catalyst showed the best bifunctional performance towards ORR and OER:an onset potential of 0.84 V vs. RHE, a half-wave potential of 0.69 V vs. RHE, and current density of -7.01 mA cm-2 at 0.50 V vs. RHE at a rotating speed of 2500 rpm and the 4e pathway for ORR, and a low overpotential (373 mV) at a current density of 10·mA cm-2 for OER. The ?E (oxygen electrode activity parameter for evaluating the overall electrocatalytic activity and reversibility of a bifunctional electrocatalyst) value for CoNx/NiFe2O4-141 is 0.84 V.