Metal pre-intercalation promotes water-mediated proton-coupled electron transfer in layered δ-MnO2 for aqueous pseudocapacitive energy storage
Year: 2026
Type: article
Abstract: The charge storage capacitance of δ-MnO 2 -based pseudocapacitors stems from a combination of bulk cation intercalation/deintercalation and surface proton chemisorption/desorption. Here, we investigate the mechanistic origins of the enhanced capacitance in δ-MnO 2 with pre-intercalated Cu 2+ . To this end, we synthesize Au-core/δ-MnO 2 -shell nanostructures with and without Cu 2+ pre-intercalation, enabling real-time in situ spectroscopic monitoring of structure-function relationships during electrochemical cycling. Transition metal pre-intercalation preserves interlayer-confined water, which in turn supports proton-coupled charge storage via the reversible reaction of MnO 2 + H 2 O + e - ⇌ MnOOH + OH - . This confined water forms a hydrogen-bonded network that lowers the energy barrier for proton transport within the interlayer space. Similar mechanistic transition is also evident in δ-MnO 2 systems pre-intercalated with other transition metal ions, such as Co 2+ and Mg 2+ . By tuning the MnO 2 shell thickness, we decouple the relative contributions of proton- and cation-driven processes, revealing that proton intercalation delivers a markedly higher specific capacitance than cation intercalation. Electrolyte-dependent studies further reveal that Cu 2+ pre-intercalation promotes OH - transport within the interlayer space while preserving proton accessibility at active sites. These findings suggest that proton-coupled transport may offer further increases in charge storage performance in pseudocapacitors.
Source: Nature Communications
Institution: Northwestern University
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $6,990
Funders: National Science Foundation, U.S. Department of Energy, Northwestern University, National Energy Research Scientific Computing Center, Total, Office of Science, Materials Research Science and Engineering Center, Harvard University, Quest High Performance Computing, Division of Materials Research, Division of Electrical, Communications and Cyber Systems
Awards: G122673668, NNCI: Soft Hybrid Nanotechnology Experimental (SHyNE) Resource, G1286236842, G1546933644, G1677143136, G1863003419, G2152989731, G2233802770, G2343375527, G2788453484, G3010471893, G3083819904, G3203750490, G3623521785, G3892126996, G3967535168, G419881185, Northwestern University Materials Research Science and Engineering Center, G42916606, G4501827968, G4796240486, G4958141111, G498139845, G5076365615, G6540817556, G6652958823, G7397830644, G969889393
OpenAlex ID: W7171497617