NC | 二维矿物水凝胶衍生的单原子锚定异质结构实现超稳定析氢反应

近日，香港城市大学-吕坚&李扬扬，哈尔滨工业大学(深圳)-孙李刚等人在Nature Communications上发表重要文章，论文题为“Two-dimensional mineral hydrogel-derived single atoms-anchored heterostructures for ultrastable hydrogen evolution”。氢能是实现碳中和的关键。具有单金属原子分散的异质结构材料是制氢的理想材料。然而，如何实现高稳定性、低成本、方便的单原子锚定异质结构催化剂的大规模制备仍然是一个巨大的挑战。在这里，作者报道了从矿物水凝胶开发的单铁(Fe)原子分散异质结构的钼基纳米片。这些合理设计的纳米片在碱性条件下表现出优异的析氢反应(HER)活性和可靠性，在10 mA cm^-2下表现出38.5 mV的过电位，在高达200 mA cm^-2的电流密度下，超过600 h时性能没有下降，优于大多数之前报道的非贵金属电催化剂。实验和密度泛函理论结果表明，o配位的单Fe原子分散异质结构极大地促进了H2O的吸附和有效吸附氢(H*)的吸附/解吸。本文报道的单原子分散异质结构HER电催化剂的绿色、可扩展生产对促进其大规模实施具有重要意义。

第一作者：Fucong Lyu

通讯作者：Ligang Sun, Yang Yang Li, Jian Lu

通讯单位：香港城市大学

论文DOI：10.1038/s41467-022-33725-8

Figure 1. a General characteristics comparison of the common substrate precursors for SACs (more details presented in Table S1); b schematic of synthesis of the Fe/SAs@Mo-based-HNSs eletrocatalyst; c SEM image, d TEM image, with inset of the SAED pattern, e high-resolution TEM image, and f STEM image of an FePMoG with an Fe3+: PMo molar ratio of 25:1, and the corresponding EDS elemental mapping of Fe (green), Mo (violet), phosphorus (P; orange), and oxygen (O; cyan).

Figure 2. a XRD patterns; b low-magnification TEM image, c SAED pattern, d high-magnification TEM image, e HRTEM image, and f HAADF-STEM image and the corresponding EDS elemental mapping of Fe (green), Mo (violet), P (orange) and O (cyan).

Figure 3. a Mo 3d XPS spectra; b Fe 2p XPS spectra; c P 2p XPS spectra; d Mo K-edge XANES spectra; e corresponding k2-weighted FT of EXAFS spectra; f wavelet transforms for k2-weighted EXAFS signals at Mo K-edge; g Fe K-edge XANES spectra; h corresponding k3-weighted FT of EXAFS spectra; and i wavelet transforms for k3-weighted EXAFS signals at Fe K-edge.

Figure 4. a Polarisation curves at a scan rate of 5 mV s−1 with potential error (iR) correction; b corresponding Tafel plots; c Electrochemical impedance spectroscopy (EIS) of the FeMoP-T samples and 20% Pt/C at an overpotential of 200 mV; d calculated electrochemical double-layer capacitance for selected as-prepared materials; e Faradaic efficiency of Fe/SAs@Mo-based-HNSs at different applied potentials. The error bar reflects the three device results; f Hydrogen production at a specific constant current density of 10 mA/cm2. The error bar reflects the three device results; g long-duration curves at a constant current density of 200 mA cm−2.

Figure 5. a DFT-calculated ΔEH2O on various exposed surfaces of MoP, MoP2, MoO2, MoP/MoP2, MoP/MoO2, MoP2/MoO2, Fe@MoO2−1, and Fe@MoO2−2, respectively. As a reference, the ΔEH2O of the Pt(111) surface is marked by the grey dashed line. b DFT-optimised atomic configurations and corresponding electron density differences for MoP (a1 and a2), MoP2 (b1 and b2), MoO2 (c1 and c2), MoP/MoP2 (d1 and d2), MoP/MoO2 (e1 and e2), MoP2/MoO2 (f1 and f2), Fe@MoO2−1 (g1 and g2), and Fe@MoO2−2 (h1 and h2), after H2O adsorption at their surface sites. Yellow isosurfaces and blue isosurfaces represent the depletion and segregation of electrons, respectively. c ΔGH* profiles of various catalytic sites at the surfaces of MoP, MoP2, MoO2, MoP/MoP2, MoP/MoO2, MoP2/MoO2, Fe@MoO2−1, and Fe@MoO2−2. d Representative atomic configurations after H* adsorption at the surface sites of MoP/MoP2, MoP/MoO2, MoP2/MoO2, Fe@MoO2−1, and Fe@MoO2−2, with corresponding ΔGH*. e DFT-calculated 2D electron density differences after adsorption of H* on active sites in heterostructured interface models and monoatomic dispersed models. Red backgrounds and blue backgrounds represent the depletion and accumulation of electrons (e/Å3), respectively.

【总结】

综上所述，作者设计了一种高效的HER电催化剂，由多孔Fe/SAs@Mo基HNSs组成，它是通过一种新型的低温磷酸化形成的环境友好和简单的自组装无机-无机配位FePMoG纳米片。在磷化过程中，通过调节温度和时间，可以很容易地调节FePMoG纳米片的孔隙率和非均相界面。因此，制备的Fe/SAs@Mo基HNSs在电流密度为10 mA cm^-2时表现出38.5 mV的过电位，Tafel斜率为35.6 mV dec^-1，在200 mA cm^-2下连续运行600小时以上，极化电位的增加可以忽略，这是迄今为止报道的纳米结构钼基电催化剂的最佳性能之一。这种优异的性能归因于Fe/SAs@Mo基HNSs 优化的电子结构，丰富的界面和边界相，大的活性表面积和孔隙率，以及它们的单个分散原子和异质结构的协同效应。实验和DFT计算表明，Fe/SAs@Mo基HNSs的异质结构界面和单一分散的Fe原子在HER过程中有利于H2O的吸附和适当的H*吸附/解吸，其多孔二维网络意味着可以充分利用其活性位点。

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