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CuO nanocone arrays were grown in situ on an FTO substrate with thicknesses of 70-600 nm via a low-temperature hydrothermal synthesis method. Their morphological, optical, photoelectrochemical, and photocatalytic performances, were studied, as well as their charge transport photoelectric conversion kinetics. The photocurrent and photocatalytic degradation rate of CuO nanocone arrays increased when the nanocone length increased from 70 to 250 nm, and continued to decrease thereafter. Electrochemical impedance spectroscopy (EIS) indicated that charge separation and transfer were improved with a higher CuO/electrolyte interface area and longer CuO nanocones. But recombination also gradually increased with an increasing CuO nanocone length. Intensitymodulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) spectra showed an increased transport time constant tIMPS with a thicker CuO array, suggesting a more difficult hole transfer with a longer transport path. In contrast, a lower recombination time constant tIMVS was observed in thicker CuO arrays, implying a more severe charge recombination, meaning that electron and hole recombination was inhibited in longer nanocones. Moreover, hole transport kinetics indicated that the low hole diffusion length was less than 50 nm, and was the likely cause of the limited photoelectric conversion in CuO nanocone arrays. [ABSTRACT FROM AUTHOR]

Electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are core materials in many renewable energy technologies including fuel cells, metal-air batteries, and water splitting devices. However, the high cost of the catalysts such as platinum and iridium oxide severely hinders the commercial development of these devices. Herein, we report a simple method for synthesizing effective bifunctional oxygen reduction and oxygen evolution catalysts through the rationally design of bimetallic metal organic framework precursor. The ratio of Zn and Co was optimized to search the critical factors affecting the catalysis of the ORR and OER. We found that for ORR catalysis, both Co/Co9S8 species and heteroatom-doped porous carbons played important roles. In contrast, the Co/Co9S8 species play more important role in OER catalysis. The optimized catalyst NSC-1-5 showed excellent ORR performance, with an onset potential of 0.879 V and a half wave potential of 0.81 V, as well as good OER catalytic activity. This was achieved simply by controlling the ratio of Co and Zn in the precursor, and NSC-1-5 could serve as a bifunctional catalyst for both ORR and OER. This work could shed some light on the design of bifunctional catalyst for both ORR and OER. [ABSTRACT FROM AUTHOR]