Electron‐Withdrawing Crystalline Pd/Amorphous PdS Drives Dynamic Electron Buffering and Sulfur Locking for Stable CO 2 ‐to‐Formate Reduction

ABSTRACT Sulfur leaching from metal sulfide electrocatalysts undermines formate intermediate stability during CO 2 reduction, yet existing protection strategies remain static. Here, we introduce an interfacial dynamic locking mechanism that actively stabilizes sulfur under reaction conditions. By constructing a crystalline‐amorphous Pd‐PdS heterostructure, the interface triggers electron redistribution from the crystalline Pd core to the amorphous PdS shell. This electron‐withdrawing effect continuously extracts electrons from the Pd core, creating an interfacial electron deficiency that drives dynamic electron buffering. This electronic buffering effect transforms the Pd core into a dynamic electron reservoir, reinforcing Pd–S bonds under operating conditions. Using crystalline Pd/amorphous PdS (c‐Pd/a‐PdS) nanowires as a model system, we demonstrate that this strategy suppresses sulfur dissolution and creates electronically optimized Pd sites favorable for formate production. At an optimal 2 nm shell thickness, the catalyst retains 90% of its initial sulfur and delivers a formate Faradaic efficiency of 77.5% at −0.6 V versus reversible hydrogen electrode, with far less sulfur leaching than a pure amorphous counterpart. Density functional theory calculations confirm this interfacial locking lowers the * OCHO formation energy by 0.35 eV while suppressing CO and H 2 pathways. This work shifts sulfur stabilization from static defense to dynamic electrochemical buffering, offering a general design principle for durable CO 2 reduction electrocatalysts.