High-Performance Overall Water Splitting Electrocatalysts Derived from Cobalt-Based Metal–Organic Frameworks

• Published in: Chemistry of materials Vol. 27; no. 22; pp. 7636 - 7642
• Main Authors: You, Bo, Jiang, Nan, Sheng, Meili, Gul, Sheraz, Yano, Junko, Sun, Yujie
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24-11-2015; American Chemical Society (ACS)
• Subjects: INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/acs.chemmater.5b02877

The design of active, robust, and nonprecious electrocatalysts with both H2 and O2 evolution reaction (HER and OER) activities for overall water splitting is highly desirable but remains a grand challenge. Herein, we report a facile two-step method to synthesize porous Co-P/NC nanopolyhedrons composed of CoP x (a mixture of CoP and Co2P) nanoparticles embedded in N-doped carbon matrices as electrocatalysts for overall water splitting. The Co-P/NC catalysts were prepared by direct carbonization of Co-based zeolitic imidazolate framework (ZIF-67) followed by phosphidation. Benefiting from the large specific surface area, controllable pore texture, and high nitrogen content of ZIF (a subclass of metal–organic frameworks), the optimal Co-P/NC showed high specific surface area of 183 m2 g–1 and large mesopores, and exhibited remarkable catalytic performance for both HER and OER in 1.0 M KOH, affording a current density of 10 mA cm–2 at low overpotentials of −154 mV for HER and 319 mV for OER, respectively. Furthermore, a Co-P/NC-based alkaline electrolyzer approached 165 mA cm–2 at 2.0 V, superior to that of Pt/IrO2 couple, along with strong stability. Various characterization techniques including X-ray absorption spectroscopy (XAS) revealed that the superior activity and strong stability of Co-P/NC originated from its 3D interconnected mesoporosity with high specific surface area, high conductivity, and synergistic effect of CoP x encapsulated within N-doped carbon matrices.