Molecular Weight Engineering Modulates Lignin‐Metal Supramolecular Framework to Construct Carbon‐Coated CoRu Alloy for Effective Overall Water Splitting

Abstract

AbstractTo overcome the challenges of low catalytic activity and instability, a molecular weight engineering strategy coupled with oxidative ammonolysis is developed to synthesize CoRu‐based alloy catalysts with distinct morphologies and properties from biorefinery lignin. This approach effectively modulates intrinsic active sites and exposes unsaturated nitrogen‐oxygen structures, thereby tailoring the morphology and defect structure of the carbon layers in the catalysts. The as‐synthesized CoRu alloy catalysts from lignin precursors with varying molecular weights are designated as CoRu@OALC‐EtOAC, CoRu@OALC‐EtOH, and CoRu@OALC‐Residual. CoRu@OALC‐EtOAC, featuring a defect‐rich graphitic carbon‐coated CoRu alloy structure, exhibited exceptional overall water‐splitting performance (1.48 V at 10 mA cm−2), significantly surpassing Pt/C || Ru/C (1.58 V at 10 mA cm−2). In contrast, CoRu@OALC‐Residual, with its amorphous carbon‐coated CoRu alloy structure, demonstrated remarkable stability (350 h at 100 mA cm−2), vastly outperforming Pt/C || Ru/C (6 h at 100 mA cm−2). In‐situ Raman spectroscopy and DFT calculations revealed that the defect‐rich carbon layers effectively adsorb *H intermediates, accelerating the catalytic process. This strong adsorption also induces carbon layer rearrangement, leading to its dissolution of the carbon layer and oxidation of CoRu metal particles. This strategy provides a universal method for biomass‐derived catalysts, establishing a direct relationship between molecular weight, catalyst morphology, and electrocatalytic performance.