Yuan Zhong, Yu Cui, Junbo Zhang, X. Wang, Xuecheng Guo, Qianqi Shi, Canyu Hu, Kun Zhou, Mingjun Shao, Wenqi Nie, Linhua Chu, Ning Zhang, Wenqing Zhang, Hengjie Liu, Ran Long, Ying Xiong
ABSTRACT The performance of scalable, catholyte‐free membrane electrode assemblies (MEAs) is restricted by insufficient interfacial water and proton supply. Here, we present a general strategy for constructing an ideal proton‐feeding microenvironment based on calcium carbonate (CaCO 3 ), an earth‐abundant mineral. Using in situ spectroscopy and theoretical simulations, we reveal that the uniquely hydrophilic surface of CaCO 3 selectively enriches and stabilizes the more mobile and reactive liquid‐like water molecules (2‐HB·H 2 O), thereby establishing an efficient proton highway near the electrode. This enables metal‐loaded CaCO 3 (M/CaCO 3 , M = Zn, and Cu) catalysts to achieve exceptional performance at industrial‐relevant current densities. Crucially, we demonstrate that the catalyst can be synthesized on a kilogram scale directly from unpurified cement plant flue gas. This catalyst enables high‐rate CO 2 conversion to C 2+ (FE C2+ 77.97%) or syngas (19 L h − 1 ; the CO/H 2 ratio ∼2) in a 100 cm 2 electrolyzer stack. This work establishes a general paradigm for using natural minerals to manipulate interfacial water dynamics for industrial electrocatalysis.