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Cathodic Electrodeposition of Ni−Mo on Semiconducting NiFe 2 O 4 for Photoelectrochemical Hydrogen Evolution in Alkaline Media
Author(s) -
Wijten Jochem H. J.,
Jong Ronald P. H.,
Mul Guido,
Weckhuysen Bert M.
Publication year - 2018
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201800112
Subject(s) - materials science , photoelectrochemistry , annealing (glass) , electrochemistry , hydrogen , nickel , water splitting , bifunctional , reversible hydrogen electrode , electrode , inorganic chemistry , analytical chemistry (journal) , chemical engineering , catalysis , metallurgy , chemistry , photocatalysis , working electrode , biochemistry , organic chemistry , chromatography , engineering
Photocathodes for hydrogen evolution from water were made by electrodeposition of Ni−Mo layers on NiFe 2 O 4 substrates, deposited by spin coating on F:SnO 2 ‐glass. Analysis confirmed the formation of two separate layers, without significant reduction of NiFe 2 O 4 . Bare NiFe 2 O 4 was found to be unstable under alkaline conditions during (photo)electrochemistry. To improve the stability significantly, the deposition of a bifunctional Ni−Mo layer through a facile electrodeposition process was performed and the composite electrodes showed stable operation for at least 1 h. Moreover, photocurrents up to −2.1 mA cm −2 at −0.3 V vs. RHE were obtained for Ni−Mo/NiFe 2 O 4 under ambient conditions, showing that the new combination functions as both a stabilizing and catalytic layer for the photoelectrochemical evolution of hydrogen. The photoelectrochemical response of these composite electrodes decreased with increasing NiFe 2 O 4 layer thickness. Transient absorption spectroscopy showed that the lifetime of excited states is short and on the ns timescale. An increase in lifetime was observed for NiFe 2 O 4 of large layer thickness, likely explained by decreasing the defect density in the primary layer(s), as a result of repetitive annealing at elevated temperature. The photoelectrochemical and transient absorption spectroscopy results indicated that a short charge carrier lifetime limits the performance of Ni−Mo/NiFe 2 O 4 photocathodes.