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Integrating various active sites into a multi-component system might significantly enhance the oxygen evolution reaction (OER) performance. Herein, the as-prepared iron-molybdenum nitride/molybdenum oxide (Fe-Mo5N6/MoO3-550) composite electrocatalyst under optimum conditions demonstrates excellent electrocatalytic performance toward OER and reaches current densities of 10 and 20 mA cm−2 at overpotentials of 201 and 216 mV, respectively. The OER performance of Fe-Mo5N6/MoO3-550 exceeds that of most previously reported electrocatalytic systems. The significant improvement in the OER performance is ascribed to a combination of mechanisms. The strong electronic interactions among the Fe, Mo5N6 and MoO3 species can accelerate the OER reaction kinetics, which contributes to the OER performance. This work provides new insights into the construction of efficient electrocatalytic materials with inexpensive metals. [ABSTRACT FROM AUTHOR]

Herein, we report a novel graphene oxide (GO) nanohybrid covalently functionalized by covalent organic polymer (COP) based on porphyrin (GO-TPPCOP), as the optical limiter and hydrogen evolution reaction (HER) electrocatalyst. The GO-TPPCOP nanohybrid exhibits markedly enhanced optical limiting and HER activity over that of TPP, GO and TPPCOP alone. More importantly, the optical limiting property and HER activity of GO-TPPCOP nanohybrid are comparable to the state-of-the-art activity of materials from some previous reports. The possible mechanisms of optical limiting and HER are explored by various means, including UV-Vis absorption, fluorescence, photocurrent, electrochemical impedance spectra and Raman spectroscopic techniques. It is demonstrated that the synergistic effect and charge transfer between GO and TPPCOP are important factors in determining its optical limiting and HER performances. These results demonstrate a new strategy to design and develop functional nanohybrids for efficient optical limiting and HER activity by the covalent linkage of GO with COPs. [ABSTRACT FROM AUTHOR]

Herein, three polypyrrole-based nanohybrids were designed and prepared via a nucleophilic substitution reaction, i.e., peripherally substituted porphyrin-functionalized PPy (TPP-PPy), axially coordinated metal-porphyrin-functionalized PPy (SnTPP-PPy), and polypyrrole ternary nanohybrids co-functionalized with peripherally substituted porphyrins and axially coordinated metal-porphyrins (TPP-PPy-SnTPP). The TPP-PPy, SnTPP-PPy and TPP-PPy-SnTPP nanohybrids exhibited improved nonlinear optical and optical limiting performances when compared to the individual PPy and porphyrins under 4 ns, 532 nm laser pulses. Their improved optical nonlinearities were ascribed to a combination of mechanisms and efficient charge transfer effect between the porphyrins and PPy. The charge transfer effect between the porphyrins and PPy was confirmed by UV-vis absorption, fluorescence and electrochemical impedance spectroscopy. The TPP-PPy-SnTPP ternary nanohybrid exhibited the best nonlinear absorption, nonlinear refraction and optical limiting performances because of more effective charge transfer effect, which provides a new avenue for the development of polypyrrole–porphyrin systems in the fields of nonlinear optics and optoelectronic devices. [ABSTRACT FROM AUTHOR]