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Revealing molecular-level surface redox sites of controllably oxidized black phosphorus nanosheets


Bulk and two-dimensional black phosphorus are considered to be promising battery materials due to their high theoretical capacities of 2,600 mAh g−1. However, their rate and cycling capabilities are limited by the intrinsic (de-)alloying mechanism. Here, we demonstrate a unique surface redox molecular-level mechanism of P sites on oxidized black phosphorus nanosheets that are strongly coupled with graphene via strong interlayer bonding. These redox-active sites of the oxidized black phosphorus are confined at the amorphorized heterointerface, revealing truly reversible pseudocapacitance (99% of total stored charge at 2,000 mV s−1). Moreover, oxidized black-phosphorus-based electrodes exhibit a capacitance of 478 F g–1 (four times greater than black phosphorus) with a rate capability of ~72% (compared to 21.2% for black phosphorus) and retention of ~91% over 50,000 cycles. In situ spectroelectrochemical and theoretical analyses reveal a reversible change in the surface electronic structure and chemical environment of the surface-exposed P redox sites.

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The data that support the findings of this study are available from the corresponding author upon reasonable request. The data are not publicly available due to restrictions (for example, information that could compromise the privacy of research participants).

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This work was supported by the R&D Convergence Program (CAP-15-02-KBSI) of the National Research Council of Science & Technology, the National Research Foundation funded by the Ministry of Science, ICT, and Future Planning (no. 2017M2A2A6A01021187) and the Energy Technology Development Project (ETDP) funded by the Ministry of Trade, Industry, and Energy (20172410100150), Republic of Korea. The authors thank the Korea Basic Science Institute for technical support and Y. Gogotsi for valuable discussions. S.K. and C.W. (DFT calculations) were supported by financial assistance award no. 70NANB14H012 from the US Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD). This research was supported in part through the computational resources and staff contributions of the Quest High Performance Computing Facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology. S.K. is grateful for discussions with V. I. Hegde, M. Liu and S. Hao at Northwestern University.

Author information

H.S.P., P.N. and X.Y. conceived and designed the experiments. P.N. and X.Y. performed sample fabrication, characterization and electrochemical measurements. P.N. and X.Y. conducted in situ Raman spectroscopy and analysed in situ Raman and in situ NMR data. S.K.P. and H.J.K. carried out in situ NMR spectroscopy. J.-Y.H., J.E.Y., J.K. and M.C. characterized bulk and 2D BP and interpreted data. W.L. and J.Y.H. carried out HAADF-STEM and EDS measurements. S.K. and C.W. performed DFT calculations and data analysis. P.N., X.Y., S.K., M.C. and H.S.P. co-wrote the paper. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to Ho Seok Park.

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Further reading

Fig. 1: Chemical structure and interaction of the foBG hybrid.
Fig. 2: Morphology and microstructure of the foBG hybrid.
Fig. 3: Electrochemical characterizations of the foBG hybrid.
Fig. 4: Pseudocapacitive features of the foBG hybrid.