3 years ago

Topotactic Engineering of Ultrathin 2D Nonlayered Nickel Selenides for Full Water Electrolysis

Topotactic Engineering of Ultrathin 2D Nonlayered Nickel Selenides for Full Water Electrolysis
Gengfeng Zheng, Ghim Wei Ho, Hao Wu, Xin Lu
Fabrication of ultrathin 2D nonlayered nanomaterials remains challenging, yet significant due to the new promises in electrochemical functionalities. However, current strategies are largely restricted to intrinsically layered materials. Herein, a combinatorial self-regulating acid etching and topotactic transformation strategy is developed to unprecedentedly prepare vertically stacked ultrathin 2D nonlayered nickel selenide nanosheets. Due to the inhibited hydrolyzation under acidic conditions, the self-regulating acid etching results in ultrathin layered nickel hydroxides (two layers). The ultrathin structure allows limited epitaxial extension during selenization, i.e., the nondestructive topotactic transformation, enabling facile artificial engineering of hydroxide foundation frameworks into ultrathin nonlayered selenides. Consequently, the exquisite nonlayered nickel selenide affords high turnover frequencies, electrochemical surface areas, exchange current densities, and low Tafel slopes, as well as facilitating charge transfer toward both oxygen and hydrogen evolution reactions. Thus, the kinetically favorable bifunctional electrocatalyst delivers advanced and robust overall water splitting activities in alkaline intermediates. The integrated methodology may open up a new pathway for designing other highly active 2D nonlayered electrocatalysts. Ultrathin 2D nonlayered NiSe nanosheets with a thickness of 1.25 nm are synthesized via a nondestructive topotactic selenization from their unconventional acid-etched ultrathin layered Ni(OH)2 counterparts. The ultrathin character of the nanosheets is responsible for the intact selenization transformation, leading to advanced bifunctional oxygen evolution reaction and hydrogen evolution reaction catalytic activities in alkaline intermediates.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201702704

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