本文要点：
共价有机骨架(COFs)由于其可调的结构和组成，经常被用于氧还原反应(ORR)以生产过氧化氢。然而，COF电催化剂需要精确的结构工程，如杂原子或金属位点掺杂，以调节ORR过程中的反应途径。
在这项工作中，作者设计了一种基于四苯基对苯二胺的COF电催化剂，即TPDA-BDA，它表现出优异的双电子(2e) ORR性能，H2O2选择性高达89.7%，法拉第效率(FE)为86.7%，高于迄今为止报道的H2O2电合成的COFs。
理论和实验结果表明，通过用联苯嵌段取代联吡啶，O2还原成OOH*中间体的限速步骤能垒显著降低，反应路径从4e变为2e ORR。此外，TPDA-BDA COF的给体-受体特性和较窄的光学带隙增强了电子导电性和还原能力，从而提高了催化活性。
结果，即使在50小时的稳定性试验后，H2O2的选择性仍保持在85%以上。这项工作揭示了COF电催化剂的结构-性能关系，并为高效和选择性生产过氧化氢的高性能2e ORR COF电催化剂的合理设计提供了新的策略。
Scheme 1. The synthetic routes and molecular structures of TPDA-BDA and TPDA-BDD COFs.
Figure 1. PXRD patterns of (a) TPDA-BDA COF and (b) TPDA-BDD COF with the experimental studies in black, Pawley-refined profiles in red, the differences between the experimental studies and refined PXRD patterns in blue, and the theoretical patterns of AAstacking in purple.
Figure 2. SEM images and the corresponding EDS mappings for C, N and O elements of (a, c) TPDA-BDD COF and (b, d) TPDA-BDA COF. TEM and HRTEM images of (e-g) TPDA-BDD COF and (h-i) TPDA-BDA COF.
Figure 3. (a) FTIR spectra; (b) N 1s high-resolution XPS spectra; (c) N2 adsorption isotherm and desorption isotherm at 77 K; (d) UV-Vis DRS diffuse reflectance spectroscopy of TPDA-BDA COF and TPDA-BDD COF; (e) The Tauc plot and (f) Mott-Schottky plot in 0.5 M Na2SO4 with scan rate 10 mV s-1 of TPDA-BDA COF.
Figure 4. (a) LSV curves collected on disk electrode; (b) LSV curves collected on ring electrode; (c) E0 and JL; (d) the electron-transfer number; (e) the H2O2 selectivity of TPDA-BDA COF and TPDA-BDD COF; (f) LSV curves of TPDA-BDA COF in an Ar-saturated 0.1 M KOH with 10 mM H2O2; (g) Durability test; (h) The Faradaic efficiency and H2O2 yield; (i) i–t plot of the H2O2 generation for TPDA-BDA COF.
Figure 5. Kohn–Sham LUMOs and HOMOs of (a) TPDA-BDD COF and (b) TPDA-BDA COF models. (c) Energy level diagram; (d) Predicted active sites; (e) Free energy diagrams; the adsorption models of intermediate OH* on (f) TPDA-BDA COF and (g) TPDA-BDD COF.
https://doi.org/10.1002/anie.202424720
