Selective Electrooxidation of Crude Glycerol to Lactic Acid Coupled With Hydrogen Production at Industrially‐Relevant Current Density

Abstract Transforming glycerol (GLY, biodiesel by‐product) into lactic acid (LA, biodegradable polymer monomer) through sustainable electrocatalysis presents an effective strategy to reduce biodiesel production costs and consequently enhance its applications. However, current research faces a trade‐off between achieving industrially‐relevant current density (>300 mA cm −2 ) and high LA selectivity (>80%), limiting technological advancement. Herein, a Au 3 Ag 1 alloy electrocatalyst is developed that demonstrates exceptional LA selectivity (85%) under high current density (>400 mA cm −2 ). The current density can further reach 1022 mA cm −2 at 1.2 V versus RHE, superior to most previous reports for GLY electrooxidation. It is revealed that the Au 3 Ag 1 alloy can enhance GLY adsorption and reactive oxygen species (OH*) generation, thereby significantly boosting activity. As a proof of concept, a homemade flow electrolyzer is constructed, achieving remarkable LA productivity of 68.9 mmol h −1 at the anode, coupled with efficient H 2 production of 3.5 L h −1 at the cathode. To further unveil the practical possibilities of this technology, crude GLY extracted from peanut oil into LA is successfully transformed, while simultaneously producing H 2 at the cathode. This work showcases a sustainable method for converting biodiesel waste into high‐value products and hydrogen fuel, promoting the broader application of biodiesel.