Abstract

Developing efficient and low-cost electrocatalysts for oxygen evolution reaction (OER) with high electrochemical activity and durability for diverse renewable and sustainable energy technologies remains challenging. Herein, an ultrasonic-assisted and coordination modulation strategy is developed to construct sandwich-like metal-organic framework (MOF) derived hydroxide nanosheet (NS) arrays/graphene oxide (GO) composite via one-step self-transformation route. Inducing from unsteady state, the dodecahedral ZIF-67 with Co²⁺ in tetrahedral coordination auto-converts into defect-rich ultrathin layered hydroxides with the interlayered ion NO₃^-. The self-transforming a-Co(OH)₂/GO nanosheet arrays from ZIF-67 (Co(OH)₂-GNS) change the coordination mode of Co²⁺ and bring about the exposure of more metal active sites, thereby enhancing the spatial utilization ratio within the framework. As monometal-based electrocatalyst, the optimized Co(OH)₂-GNS exhibits remarkable OER catalytic performance evidenced by a low overpotential of 259 mV to achieve a current density of 10 mA·cm^-2 in alkaline medium, even exceeding commercial RuO₂. During the oxygen evolution process, electron migration can be accelerated by the interfacial/in-plane charge polarization and local electric field, corroborated by the off-axis electron holography. Density functional theory (DFT) calculations further studied the collaboration between ultrathin Co(OH)₂ NS and GO, which leads to lower energy barriers of intermediate products and greatly promotes electrocatalytic property.

中文翻译：

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由金属-有机骨架改性的具有三明治结构的氧化石墨烯自转化的超薄α-Co（OH）2纳米片阵列，可有效地电催化释放氧气

摘要

为各种可再生能源和可持续能源技术开发具有高电化学活性和耐久性的用于氧气析出反应（OER）的高效，低成本电催化剂仍然具有挑战性。本文提出了一种超声辅助配位调制策略，通过一步自转化构筑三明治结构的金属有机骨架（MOF）衍生的氢氧化物纳米片（NS）阵列/氧化石墨烯（GO）复合材料。从不稳定状态诱导，十二面体ZIF-67的Co ²⁺在四面体自动转换成富含缺陷的超薄层状氢氧化物与层间离子NO ₃ ^- 。ZIF-67（Co（OH）₂的自转变a-Co（OH）₂ / GO纳米片阵列-GNS）改变了Co ²⁺的配位方式，并使更多的金属活性位点暴露，从而提高了框架内的空间利用率。作为单金属基电催化剂，优化的Co（OH）₂ -GNS具有出色的OER催化性能，其低电位为259 mV，可在碱性介质中达到10 mA·cm ^-2的电流密度，甚至超过了工业RuO ₂。在氧气析出过程中，界面迁移/面内电荷极化和局部电场可加速电子迁移，偏轴电子全息图可证实这一点。密度泛函理论（DFT）计算进一步研究了超薄Co（OH）₂之间的协同作用 NS和GO降低了中间产物的能垒并大大提高了电催化性能。