Layered solid Brønsted acid for dynamic interfacial pH regulation toward durable zinc anodes

Aqueous zinc-ion batteries (AZIBs) are promising candidates for large-scale grid energy storage due to their inherent safety, durability, and low cost. However, their practical performance is hampered by the hydrogen evolution reaction (HER) on the Zn anode, which causes unstable Zn/electrolyte interfacial pH values, resulting in the formation of byproducts and uncontrollable Zn dendrite growth. To address these issues, we developed a layered solid Brønsted acid HNbMoO₆·H₂O (HNM) for interfacial pH regulation and Zn anode protection. Density functional theory (DFT) calculations suggested that the strong adsorption of OH^- ions by HNM (E_ads = -4.15 eV) and the presence of abundant interlayer hydrated protons in HNM facilitated effective adsorption and neutralization of OH^- ions, thereby offering stable interfacial pH values, preventing alkaline byproduct formation and suppressing tip-induced dendrite growth. Moreover, the layered HNM established stable ion transport channels, enabling ordered Zn²⁺ flux and homogeneous Zn²⁺ deposition. Notably, HNM simultaneously inhibited the HER and accelerated the Zn²⁺/Zn plating/stripping kinetics. Consequently, HNM@Zn enabled an excellent Coulombic efficiency of 99.7% (over 1000 cycles) in asymmetrical cells, an exceptional Zn²⁺ transference number of 0.79 and stable cycling for over 1750 hours in symmetrical cells, retaining a capacity of 130 mAh g^-1 after 1000 cycles in HNM@Zn||α-MnO₂ full cells. This work provides insights into multifunctional anode engineering for interfacial pH regulation towards high-performance AZIBs.