No abstract

Developing an efficient and low-cost synthetic approach to controllably synthesize non-precious-metal counter electrode (CE) electrocatalysts with superior catalytic activity and electrochemical stability is critically important for the mass production of dye-sensitized solar cells (DSSCs). Herein, we proposed a simple, economical, and easily scalable synthetic route for copyrolysis of melamine and nickel acetate precursors to access the well-defined Ni-encapsulated and nitrogen-doped carbon nanotubes (Ni-NCNTs). The synthetic mechanism was comprehensively investigated by creatively analyzing the phase structure evolution and dynamical decomposition behaviors, and revealed the construction of Ni-NCNTs based on the Ni-catalyzed tip-growth mechanism. Furthermore, the meticulous structural design of Ni nanoparticles intercalated in N-doped CNTs endows Ni-NCNTs with homogeneously distributed Ni–C interfaces, abundant structural defects, and a porous architecture, as well as good electrical conductivity and corrosion-resistance properties. When used as counter electrode for DSSCs, the device delivers a high power conversion efficiency of 8.94% under simulated sunlight (AM 1.5, 100 mW cm–2) and long-term stability with a remnant efficiency of 8.34% after 100 h of illumination, superior to those of conventional Pt. The outstanding catalytic performance of Ni-NCNTs was mainly attributed to the synergetic effect of intercalated Ni with N-doped CNTs at the unique Ni–C interfaces, and the concomitant electronic interaction of Ni and N with C atoms in the interfacial nanoregime. The systematic studies on the synthetic mechanism and structure–activity relationship provide a new insight into the rational design of structural and electronic properties for high-performance Ni-NCNT CEs, as well as into the fundamental understanding of their catalytic mechanism for triiodide reduction.

Ultralight benzoxazine-derived porous nitrogen self-doped carbon aerogels with good yield can be prepared by direct polymerization of trifunctional benzoxazine monomers under acid catalysis using concentrated hydrochloric acid. This allows for a significantly widened density range (0.8-4.5 mg cm-3) and avoids any sacrificial etching. When serving as electrode materials for supercapacitors, the resulting hierarchical porous carbon aerogels show ultrahigh specific capacitance, excellent rate performance and good cycling stability (retention of 97.3% even after 10 000 continuous charge-discharge cycles). Besides energy storage devices, the interconnected nanoporous carbon aerogels can also find applications in oil/water separation, heavy metal removal, catalyst supports, and so forth.