TY - JOUR AU - Zhang, Dongbin AU - Han, Xuzhao AU - Kong, Xianggui AU - Zhang, Fazhi AU - Lei, Xiaodong PY - 2020/05/06 Y2 - 2024/03/29 TI - The Principle of Introducing Halogen Ions Into β-FeOOH: Controlling Electronic Structure and Electrochemical Performance JF - Nano-Micro Letters JA - Nano-Micro Lett VL - 12 IS - SE - Articles DO - 10.1007/s40820-020-00440-2 UR - https://nmlett.org/index.php/nml/article/view/450 SP - 107 AB - <p>Coordination tuning electronic structure of host materials is a quite effective strategy for activating and improving the intrinsic properties. Herein, halogen anion (X<sup>−</sup>)-incorporated β-FeOOH (β-FeOOH(X), X = F<sup>−</sup>, Cl<sup>−</sup>, and Br<sup>−</sup>) was investigated with a spontaneous adsorption process, which realized a great improvement of supercapacitor performances by adjusting the coordination geometry. Experiments coupled with theoretical calculations demonstrated that the change of Fe–O bond length and structural distortion of β-FeOOH, which is rooted in halogen ions embedment, led to the relatively narrow band gap. Because of the strong electronegativity of X<sup>−</sup>, the Fe element in β-FeOOH(X)s presented the unexpected high valence state (3 + <em>δ</em>), which is facilitating to adsorb SO<sub>3</sub><sup>2−</sup> species. Consequently, the designed β-FeOOH(X)s exhibited the good electric conductivity and enhanced the contact between electrode and electrolyte. When used as a negative electrode, the β-FeOOH(F) showed the excellent specific capacity of 391.9&nbsp;F&nbsp;g<sup>−1</sup> at 1&nbsp;A&nbsp;g<sup>−1</sup> current density, almost tenfold improvement compared with initial β-FeOOH, with the superior rate capacity and cyclic stability. This combinational design principle of electronic structure and electrochemical performances provides a promising way to develop advanced electrode materials for supercapacitor.</p><p>Highlights:</p><p>1 Halogen ion-incorporated β-FeOOH(X)s (X = F−, Cl−, Br−) were designed and fabricated successfully and showed good performance for negative electrodes of supercapacitors.<br>2 The embedment of X− caused the change of Fe–O bond length and structural distortion of β-FeOOH, which resulted in the narrow band gap and good electric conductivity.<br>3 The presence of unexpected high valence state (3 + δ) Fe element facilitated the adsorption for SO<sub>3</sub><sup>2−</sup> species endowing the β-FeOOH(X)s with good wettability in Na<sub>2</sub>SO<sub>3</sub> electrolyte.</p> ER -