Daxiang Gui, Xing Dai, Zetian Tao, Tao Zheng, Xiangxiang Wang, Mark A. Silver Orcid, Jie Shu, Lanhua Chen, Yanlong Wang, Tiantian Zhang, Jian Xie, Lin Zou, Yuanhua Xia, Jujia Zhang, Jin Zhang, Ling Zhao*, Juan Diwu, Ruhong Zhou*, Zhifang Chai and Shuao Wang*

Abstract

Although comprehensive progress has been made in the area of coordination polymer (CP)/metal−organic framework (MOF)-based proton-conducting materials over the past decade, searching for a CP/MOF with stable, intrinsic, high anhydrous proton conductivity that can be directly used as a practical electrolyte in an intermediate-temperature proton-exchange membrane fuel cell assembly for durable power generation remains a substantial challenge. Here, we introduce a new protonconducting CP, (NH₄)₃[Zr(H_2/3PO₄)₃] (ZrP), which consists ofone-dimensional zirconium phosphate anionic chains and fully ordered charge-balancing NH4⁺ cations. X-ray crystallography, neutron powder diffraction, and variable-temperature solid-state NMR spectroscopy suggest that protons are disordered within an inherent hydrogen-bonded infinite chain of acid−base pairs (N−H···O−P), leading to a stable anhydrous proton conductivity of 1.45×10⁻³S·cm⁻¹ at 180°C, one of the highest values among reported intermediate-temperature proton-conducting materials. First-principles and quantum molecular dynamics simulations were used to directly visualize the unique proton transport pathway involving very efficient proton exchange between NH₄⁺ and phosphate pairs, which is distinct from the common guest encapsulation/dehydration/superprotonic transition mechani**s. ZrP as the electrolyte was further assembled into a H₂/O₂ fuel cell, which showed a record-high electrical power density of 12 mW·cm⁻² at 180 °C among reported cells assembled from crystalline solid electrolytes, as well as a direct methanol fuel cell for thefirst time to demonstrate real applications. These cells were tested for over 15 h without notable power loss.