Title: Copper-Intercalated Birnessite as a Water Oxidation Catalyst

Abstract

Here, we report a synthetic method to increase the catalytic activity of birnessite toward water oxidation by intercalating copper in the interlayer region of the layered manganese oxide. Intercalation of copper, verified by XRD, XPS, ICP, and Raman spectroscopy, was accomplished by exposing a suspension of birnessite to a Cu⁺-bearing precursor molecule that underwent disproportionation in solution to yield Cu⁰ and Cu²⁺. Electrocatalytic studies reflected that the Cu-modified birnessite exhibited an overpotential for water oxidation of ~490 mV (at 10 mA/cm²) and a Tafel slope of 126 mV/decade compared to ~700 mV (at 10 mA/cm²) and 240 mV/decade, respectively, for birnessite without copper. Impedance spectroscopy results suggested that the charge transfer resistivity of the Cu-modified sample was significantly lower than Cu-free birnessite, suggesting that Cu in the interlayer increased the conductivity of birnessite leading to an enhancement of water oxidation kinetics. Density functional theory calculations show that the intercalation of Cu⁰ into a layered MnO₂ model structure led to a change of the electronic properties of the material from a semiconductor to a metallic-like structure. This conclusion from computation is in general agreement with the aforementioned impedance spectroscopy results. X-ray photoelectron spectroscopy (XPS) showed that Cu⁰ coexisted with Cu²⁺ inmore » the prepared Cu-modified birnessite. Control experiments using birnessite that was decorated with only Cu²⁺ showed a reduction in water oxidation kinetics, further emphasizing the importance of Cu⁰ for the increased activity of birnessite. The introduction of Cu⁰ into the birnessite structure also increased the stability of the electrocatalyst. At a working current of 2 mA, the Cu-modified birnessite took ~3 times longer for the overpotential for water oxdiation to increase by 100 mV compared to when Cu was not present in the birnessite.« less

Authors:

Thenuwara, Akila C. ^[1]; Shumlas, Samantha L. ^[1]; Attanayake, Nuwan H. ^[1]; Cerkez, Elizabeth B. ^[1]; McKendry, Ian G. ^[1]; Frazer, Laszlo ^[1]; Borguet, Eric ^[1]; Kang, Qing ^[1]; Zdilla, Michael J. ^[1]; Sun, Jianwei ^[1]; Strongin, Daniel R. ^[1]

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+ Show Author Affiliations

1. Temple Univ., Philadelphia, PA (United States)

Publication Date:

Mon Oct 19 00:00:00 EDT 2015

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Center for the Computational Design of Functional Layered Materials (CCDM)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1371092

Grant/Contract Number:  

SC0012575

Resource Type:

Accepted Manuscript

Journal Name:

Langmuir

Additional Journal Information:

Journal Volume: 31; Journal Issue: 46; Related Information: CCDM partners with Temple University (lead); Brookhaven National Laboratory; Drexel University; Duke University; North Carolina State University; Northeastern University; Princeton University; Rice University; University of Pennsylvania; Journal ID: ISSN 0743-7463

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY