The rational design of highly efficient and stable electrodes is necessary for energy storage and electrocatalysis. Herein, we developed a nanometre thin bimetallic ultrathin Co_xNi_1−x(OH)₂ nanosheet with a large lateral size by the ionic layer epitaxy (ILE) technique as an efficient bifunctional electrode material for pseudocapacitors and the oxygen evolution reaction. Its electrochemical performance was readily tuned by controlling the Co/Ni ratio. The nanosheet with a 1 : 3 Co : Ni ratio (termed Co₁Ni₃-NS) showed an excellent volumetric (areal) capacitance of 3783 F cm⁻³ (3 mF cm⁻²) at 0.3 mA cm⁻² with 336 mW h cm⁻³ energy density at 256 W cm⁻³ power density and excellent stability, substantially outperforming other monometallic and bimetallic NSs. Moreover, as an electrocatalyst, Co₁Ni₃-NS delivered a lower overpotential (η₁₀ = 318 mV) and Tafel slope (61 mV dec⁻¹) in an alkaline environment. In situ Raman spectroscopy was employed to demonstrate the dynamic structural evolution of the catalyst during the OER process. Furthermore, DFT investigations further revealed that Co₁Ni₃-NS is a promising electrode with higher quantum capacitance and lower overpotential compared to other Co/Ni ratios. These findings pave a new way for controlled synthesis of highly efficient, bimetallic, and bifunctional electrode materials for pseudocapacitors and the OER.

中文翻译：

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揭示超薄双金属 CoxNi1−x（OH）2 纳米片用于伪电容器和析氧反应的性能


高效稳定的电极的合理设计对于储能和电催化是必要的。在此，我们通过离子层外延 （ILE） 技术开发了一种具有大横向尺寸的纳米薄双金属超薄 Co_xNi_1−x（OH）₂ 纳米片，作为用于伪电容器和析氧反应的高效双功能电极材料。通过控制 Co/Ni 比率，可以很容易地调整其电化学性能。具有 1 ： 3 Co ： Ni 比率的纳米片（称为 Co₁Ni_3-NS）在 0.3 mA ^cm-2 时显示出 3783 F ^cm-3 （3 mF ^cm-2） 的出色体积（面）电容，在 256 W ^cm-3 时具有 336 mW h ^cm-3 的能量密度功率密度和出色的稳定性，大大优于其他单金属和双金属 NS。此外，作为电催化剂，Co₁Ni_3-NS 在碱性环境中提供较低的过电位 （η₁₀ = 318 mV） 和塔菲尔斜率 （61 mV ^dec-1）。原位拉曼光谱用于证明 OER 过程中催化剂的动态结构演变。此外，DFT 研究进一步表明，与其他 Co/Ni 比率相比，Co₁Ni_3-NS 是一种很有前途的电极，具有更高的量子电容和更低的过电位。 这些发现为赝电容器和 OER 的高效、双金属和双功能电极材料的受控合成铺平了一条新道路。