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Charge Transfer Kinetics of Photo‐Electrochemical Hydrogen Evolution Improved by Nonstoichiometric Ni‐rich NiO x ‐Coated Si Photocathode in Alkaline Electrolyte
Author(s) -
Jung JinYoung,
Yu JinYoung,
Yoon Sanghwa,
Yoo Bongyoung,
Lee JungHo
Publication year - 2018
Publication title -
advanced sustainable systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.499
H-Index - 24
ISSN - 2366-7486
DOI - 10.1002/adsu.201700138
Subject(s) - photocathode , non blocking i/o , electrolyte , photocurrent , materials science , electrochemistry , reversible hydrogen electrode , hydrogen , electrocatalyst , inorganic chemistry , analytical chemistry (journal) , chemistry , electrode , catalysis , working electrode , optoelectronics , electron , biochemistry , physics , organic chemistry , quantum mechanics , chromatography
The integration of electrocatalyst (EC) with light‐absorbing semiconductor photoelectrode is regarded as a representative framework for photoelectrochemical (PEC) devices. When considering the charge transfer pathways, PEC performance is governed by the charge kinetics at the EC/electrolyte and the semiconductor/EC interfaces. Here, systematic investigations are reported, made on the overall kinetics of the PEC hydrogen evolution reaction (HER) in an alkaline electrolyte. A non‐stoichiometric (Ni‐rich) NiO x ( x < 1) EC is deposited on a Si photocathode passivated with a SiO x layer. A few distinctive features of the Ni‐rich NiO x film are identified in contrast with the conventional O‐rich NiO y ( y ≥ 1) which could lower the series resistance along the charge transfer pathways. The Ni‐rich NiO x is found to possess both NiO and NiNi (by oxygen‐vacancy) bonds, which act as suitable catalytic sites for dissociating water molecules and recombining two hydrogen atoms, respectively. In addition, the Ni‐rich NiO x reveals both n‐type and metallic conduction behavior, a feature that may contribute to lowering bulk resistance as well as tunneling resistance through SiOx layer. As a result, this noble metal‐free EC‐integrated Si photocathode achieves the highest potential of 0.41 V vs. reversible hydrogen electrode to produce a photocurrent density of 10 mA cm 2 .