Engineering p-Orbital States via Molecular Modules in All-Organic Electrocatalysts toward Direct Water Oxidation

Oxygen evolution reaction (OER) is an indispensable anode reaction for sustainable hydrogen production from water electrolysis, yet overreliance on metal-based catalysts featured with vibrant d-electrons. It still has notable gap between metal-free and metal-based electrocatalysts, due to lacking accurate and efficient p-band regulation methods on non-metal atoms. Herein, a molecular modularization strategy is proposed for fine-tuning the p-orbital states of series metal-free covalent organic frameworks (COFs) for realizing OER performance beyond benchmark precious metal catalysts. Optimized combination of benzodioxazole/benzodiimide-based building blocks achieves an impressive applied potential of 1.670 ± 0.004 V versus reversible hydrogen electrode (RHE) and 1.735 ± 0.006 V versus RHE to deliver enhanced current densities of 0.5 and 1.0 A cm^-2, respectively. Moreover, it holds a notable charge transfer amount (stands for a long service life) within operation period that outperforms all reported metal-free electrocatalysts. Operando differential electrochemical mass spectrometry (DEMS) with isotope labeling identifies the adsorbate evolution mechanism (AEM). A variety of spectroscopic techniques and density functional theory (DFT) calculations reveal that the p-band center of these catalysts can be shifted stepwise to optimize the oxygen intermediate adsorption and lower the reaction energy barrier. This work provides a novel perspective for enhancing the electrocatalytic performance of metal-free COFs.