Controlled Synthesis of Nickel Encapsulated into Nitrogen-Doped Carbon Nanotubes with Covalent Bonded Interfaces: The Structural and Electronic Modulation Strategy for an Efficient Electrocatalyst in Dye-Sensitized Solar Cells

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.

Three-dimensional graphene networks and RGO-based counter electrode for DSSCs

“…Moreover, the good interface condition between the Ni and 3DGNs was also advantageous for the electron transport. 35,36 As expected, the combination of the RGO and 3DGNs brought about a remarkable enhancement of the performance of the resulting DSSCs (Table 1, a h as high as 9.42% was achieved), implying the achieved synergy of the 3DGNs and RGO. Cyclic voltammetry is widely used to analyze the electrocatalytic activities of CEs.…”

Assemblage of Perovskite LaNiO3 Connected With In Situ Grown Nitrogen‐Doped Carbon Nanotubes as High‐Performance Electrocatalyst for Oxygen Evolution Reaction

“…The peaks of the N 1s (Figure f) located at 398.6, 400.7, 401.5, and 404.6 eV correspond to pyridinic, pyrrolic, quaternary, and pyrrolidone . It is well known that pyridinic nitrogen could improve the structural defect density, and thus provides more active sites as catalysts in some other reactions …”

Enhanced electrocatalytic performance of nickel diselenide grown on graphene toward the reduction of triiodide redox couples

“…16,33 Simultaneously, from the parameters in Table 1, the R ct value of NiSe 2 /RGO NPs CE (R ct ¼ 1.52 U cm À2 ) is also lower than that of NiSe 2 NPs CE (R ct ¼ 3.82 U cm À2 ), and even inferior to that of Pt CE (R ct ¼ 1.72 U cm À2 ), indicative of its supreme electrocatalytic activity for triiodide reduction. 19,34 The integration of low R ct and R S of NiSe 2 /RGO NPs CE can efficiently lower the charge transfer resistance and facilitate the transfer of electron, thus contributing to the improvement of the electrocatalytic performance of DSSCs. 35 Tafel polarization measurement is an effective technique for examining the charge-transfer kinetics of CEs.…”