Title: Dye-sensitized photocathodes for oxygen reduction: efficient H ₂ O ₂ production and aprotic redox reactions

Abstract

Dye-sensitized photoelectrochemical cells (DSPECs) can be used to store solar energy in the form of chemical bonds. Hydrogen peroxide (H₂O₂) is a versatile energy carrier and can be produced by reduction of O₂ on a dye-sensitized photocathode, in which the design of dye molecules is crucial for the conversion efficiency and electrode stability. Herein, using a hydrophobic donor-double-acceptor dye (denoted as BH4) sensitized NiO photocathode, hydrogen peroxide (H₂O₂) can be produced efficiently by reducing O₂ with current density up to 600 μA cm^-2 under 1 sun conditions (Xe lamp as sunlight simulator, λ > 400 nm). The DSPECs maintain currents greater than 200 μA cm^-2 at low overpotential (0.42 V vs. RHE) for 18 h with no decrease in the rate of H₂O₂ production in aqueous electrolyte. Moreover, the BH4 sensitized NiO photocathode was for the first time applied in an aprotic electrolyte for oxygen reduction. In the absence of a proton source, the one-electron reduction of O₂ generates stable, nucleophilic superoxide radicals that can then be synthetically utilized in the attack of an available electrophile, such as benzoyl chloride. The corresponding photocurrent generated by this photoelectrosynthesis is up to 1.8 mA cm^-2. Transient absorption spectroscopy also proves that theremore » is an effective electron transfer from reduced BH4 to O₂ with a rate constant of 1.8 × 10⁶ s^-1. This work exhibits superior photocurrent in both aqueous and non-aqueous systems and reveals the oxygen/superoxide redox mediator mechanism in the aprotic chemical synthesis.« less

Authors:

Sun, Jiaonan  ^[1];

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Yu, Yongze ^[1]; Curtze, Allison E. ^[1]; Liang, Xichen ^[1]; Wu, Yiying ^[1]

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+ Show Author Affiliations

1. Department of Chemistry and Biochemistry, The Ohio State University, Columbus, USA

Publication Date:

Wed May 29 00:00:00 EDT 2019

Research Org.:

The Ohio State Univ., Columbus, OH (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)

Sponsoring Org.:

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

OSTI Identifier:

1510536

Alternate Identifier(s):

OSTI ID: 1609888

Grant/Contract Number:  

FG02-07ER46427; AC02-06CH11357

Resource Type:

Published Article

Journal Name:

Chemical Science

Additional Journal Information:

Journal Name: Chemical Science Journal Volume: 10 Journal Issue: 21; Journal ID: ISSN 2041-6520

Publisher:

Royal Society of Chemistry

Country of Publication:

United Kingdom

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Chemistry