Reimagining the eg1 Electronic State in Oxygen Evolution Catalysis: Oxidation‐State‐Modulated Superlattices as a New Type of Heterostructure for Maximizing Catalysis. Issue 41 (1st October 2021)

• Record Type: Journal Article
• Authors: Ding, Ran; Yasini, Parisa; Peng, Haowei; Perdew, John P.; Borguet, Eric; Zdilla, Michael J.
• Is Part Of: Advanced energy materials. Volume 11:Issue 41(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-01
• Subjects: catalysis -- electrochemistry -- layered materials -- manganese oxides -- oxygen evolution reaction -- scanning tunneling spectroscopy -- water oxidation; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202101636
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: The discovery of solid‐phase, inexpensive transition‐metal‐based water oxidation catalysts is a central goal for renewable energy, and has led to a general consensus that a partially populated metal eg d ‐electronic state is desirable, leading to favorable catalysis for certain elements in specific oxidation states. In manganese systems, the key species is manganese(III), whose high‐spin d 4 electronic configuration places an unpaired electron in the eg orbital, which is postulated to contribute to electronic and structural features that support catalysis. Based on density functional theory calculations, it is predicted that electron transfer would be facilitated by a catalyst with alternating low‐ and high‐Mn III ‐content sheets, which positions neighboring band edges in closer energetic proximity. The preparation of such catalysts is demonstrated for the first time and it is shown that the catalytic activity is maximized in these systems over more uniform, but more Mn III ‐rich systems. The best catalyst possesses alternating high‐and low‐average oxidation state sheets with interlayer Cs + ions, and has an overpotential of 450 mV at 10 mA, which represents an improvement of 250 mV over the best unmodified synthetic potassium birnessites. Using scanning tunneling spectroscopy, bandgap modulations consistent with the theoretically predicted band edge shifts are detected. Abstract : The oxygen evolution reaction is the most challenging barrier to solar water splitting, and first‐row transition elements with an unequally populated e g 1 electronic state (such as manganese(III)) are known to be important for catalysis. Here, it is demonstrated that the non‐uniform distribution of these Mn III ions is more important than their total abundance in the catalytic material.