Spinel structural disorder influences solar-water-splitting performance of ZnFe2O4 nanorod photoanodes

Impact Factor:

30.849

DOI number:

10.1002/adma.201801612

Journal:

Adv. Mater.

Key Words:

Cation inversion degree, charge transport, crystallinity, nanostructured photoelectrodes, ternary metal oxide semiconductors

Abstract:

Abstract Zinc spinel ferrite, ZnFe2O4 (ZFO), is an emerging photoanode material for photoelectrochemical (PEC) solar fuel production. However, a lack of fundamental insight into the factors limiting the photocurrent has prevented substantial advance in its performance. Herein, it is found that ZFO nanorod array photoelectrodes with varying crystallinity exhibit vastly different PEC properties. Using a sacrificial hole scavenger (H2O2), spatially defined carrier generation, and electrochemical impedance spectroscopy, it is shown that ZFO with a relatively poor crystallinity but a higher spinel inversion degree (due to cation disorder) exhibits superior photogenerated charge separation efficiency and improved majority charge carrier transport compared to ZFO with higher crystallinity and a lower inversion degree. Conversely, the latter condition leads to better charge injection efficiency. Optimization of these factors, and the addition of a nickel?iron oxide cocatalyst overlayer, leads to a new benchmark solar photocurrent for ZFO of 1.0 mA cm?2 at 1.23 V versus reversible hydrogen electrode (RHE) and 1.7 mA cm?2 at 1.6 V versus RHE. Importantly, the observed correlation between the cation disorder and the PEC performance represents a new insight into the factors important to the PEC performance of the spinel ferrites and suggests a path to further improvement. ER -

Co-author:

Yongpeng Liu, Pascal Schouwink, Rebekah A. Wells, Florian Le Formal, Song Sun, Chen Gao

First Author:

Xiaodi Zhu

Correspondence Author:

Néstor Guijarro, Kevin Sivula

Document Code:

1802359

Volume:

30

Issue:

34

Page Number:

1801612

ISSN No.:

0935-9648

Translation or Not:

no

Date of Publication:

2018-07-05

Links to published journals:

https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201801612