Enhanced Mass Transport and Elevated Active Site Density for Highly Efficient Overall Water Splitting Over Delignification‐Engineered Carbonized Wood

ABSTRACT Wood‐based materials, with a naturally intrinsic hierarchical porous structure, are recognized as exceptional water‐splitting electrocatalyst supports for green hydrogen production. However, lignin, as the structural binding agent within its native architecture, occludes pores and restricts the anchoring of active sites. Here, controllable delignification pretreatment is used to enable the simultaneous modulation of pore architecture for efficient mass transport and improve the anchoring environment to boost active site density. When the lignin removal rate reaches 65.55%, Ni/Ni(OH) 2 ‐DCW‐45 shows hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of 147 and 162 mV at 100 mA·cm −2 , respectively. These overpotentials are reduced by 49.83% and 34.94% compared to Ni/Ni(OH) 2 ‐CW. As a unified cathode/anode in alkaline electrolysis, it drove full water splitting at 1.363 V (10 mA·cm −2 ) with 48‐h stability. Both experimental and DFT calculations reveal that delignification regulates the Ni/Ni(OH) 2 ratio, promotes charge transfer, and strengthens the interaction between reaction intermediates and catalytic sites. This electronic modulation lowered the energy barriers of HER and OER, thereby enhancing the overall water‐splitting performance. This work exploits wood's structural advantages and validates delignification as a powerful tool for synergistic optimization of mass transport and active site density, providing novel insights for high‐performance biomass‐based electrocatalyst design.