The performance of single-atom catalysts is greatly influenced by the chemical environment surrounding the central atom. Here, a salt-assisted method is employed to transform the tetrahedral coordination structure of zeolitic imidazolate frameworks - 8 (ZIF-8) into a planar square coordination structure without altering the ligands. During the subsequent carbonization process, concurrent with the evaporation of zinc atoms, the structure of the nitrogen and carbon carriers (NC carriers) undergoes a transition from five-membered rings to six-membered rings to preserve the 2D structure. This transition results in the generation of additional defect sites on the 2D-NC substrates. Hence, the Pt single-atom catalysts with planar square coordination symmetries can be precisely prepared via electrodeposition (denoted as 2D-Pt SAC). The Pt loading of 2D-Pt SAC is 0.49 ± 0.03 µg cm⁻², higher than that of 3D-Pt SAC (0.37 ± 0.04 µg cm⁻²). In the context of the hydrogen oxidation reaction electrocatalysis, under an overpotential of 50 mV, these single-atom catalysts with 2D coordination exhibit mass activities of 2396 A g_Pt⁻¹ (32 times higher than commercial Pt/C catalyst, 2 times higher than 3D-PtNC).

中文翻译：

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对称演化诱导的高密度二维 Pt 单原子催化剂用于碱性氢氧化

单原子催化剂的性能很大程度上受中心原子周围的化学环境影响。在这里，采用盐辅助方法将沸石咪唑酯骨架-8（ZIF-8）的四面体配位结构转变为平面方形配位结构，而不改变配体。在随后的碳化过程中，与锌原子蒸发同时，氮和碳载体（NC载体）的结构经历从五元环到六元环的转变，以保持二维结构。这种转变导致 2D-NC 基板上产生额外的缺陷位点。因此，可以通过电沉积精确制备具有平面方形配位对称性的Pt单原子催化剂（表示为2D-Pt SAC）。 2D-Pt SAC 的 Pt 负载量为 0.49 ± 0.03 µg cm ^-2，高于 3D-Pt SAC 的 Pt 负载量（0.37 ± 0.04 µg cm ^-2）。在电催化氢氧化反应中，在50 mV的过电势下，这些具有2D配位的单原子催化剂表现出2396 A g _Pt ^-1的质量活性（比商业Pt/C催化剂高32倍，比商业Pt/C催化剂高2倍） 3D-PtNC）。