Electrocatalytic two‐electron reduction of oxygen is a promising method for producing sustainable H2O2but lacks low‐cost and selective electrocatalysts. Here, the Chevrel phase chalcogenide Ni2Mo6S8is presented as a novel active motif for reducing oxygen to H2O2in an aqueous electrolyte. Although it has a low surface area, the Ni2Mo6S8catalyst exhibits exceptional activity for H2O2synthesis with >90% H2O2molar selectivity across a wide potential range. Chemical titration verified successful generation of H2O2and confirmed rates as high as 90 mmol H2O2gcat−1h−1. The outstanding activities are attributed to the ligand and ensemble effects of Ni that promote H2O dissociation and proton‐coupled reduction of O2to HOO*, and the spatial effect of the Chevrel phase structure that isolates Ni active sites to inhibit OO cleavage. The synergy of these effects delivers fast and selective production of H2O2with high turn‐over frequencies of ≈30 s−1. In addition, the Ni2Mo6S8catalyst has a stable crystal structure that is resistive for oxidation and delivers good catalyst stability for continuous H2O2production. The described Ni‐Mo6S8active motif can unlock new opportunities for designing Earth‐abundant electrocatalysts to tune oxygen reduction for practical H2O2production.
H2W2O7, a metastable material synthesized via selective etching of the Aurivillius‐related Bi2W2O9, is demonstrated as an electrode for high power proton‐based energy storage. Comprehensive structural characterization is performed to obtain a high‐fidelity crystal structure of H2W2O7using an iterative approach that combines X‐ray diffraction, neutron pair distribution function, scanning transmission electron microscopy, Raman spectroscopy, and density functional theory modeling. Electrochemical characterization shows a capacity retention of ≈80% at 1000 mV s–1(1.5‐s charge/discharge time) as compared to 1 mV s–1(≈16‐min charge/discharge time) with cyclability for over 100 000 cycles. Energetics from density functional theory calculations indicate that proton storage occurs at the terminal oxygen sites within the hydrated interlayer. Last, optical micrographs collected during in situ Raman spectroscopy show reversible, multicolor electrochromism, with color changes from pale yellow to blue, purple, and last, orange as a function of proton content. These results highlight the use of selective etching of layered perovskites for the synthesis of metastable transition metal oxide materials and the use of H2W2O7as an anode material for proton‐based energy storage or electrochromic applications.
more » « less- PAR ID:
- 10447405
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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