THESIS
2018
xv, 90 pages : illustrations (chiefly color) ; 30 cm
Abstract
Oxygen evolution reaction (OER) is essential to energy conversion and storage technologies. Up to date, the most active catalysts for OER are noble metal based catalysts, including iridium oxide and ruthenium oxide, however the scarcity and high expenses greatly hinder their large-scale application. The objective of this thesis is to develop high efficiency and low cost nanomaterials as an alternative to noble metal based electrocatalysts for OER.
Chapter one surveys the background of OER and the development of OER catalysts. In chapter two, carbon black-supported nickel sulfide-derived nanoparticles (NiS/CB(st)-DNs) were developed as electrocatalysts for OER under alkaline condition. The carbon black-supported nickel sulfide (NiS/CB(st)) were synthesized via a one-step solvothermal...[
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Oxygen evolution reaction (OER) is essential to energy conversion and storage technologies. Up to date, the most active catalysts for OER are noble metal based catalysts, including iridium oxide and ruthenium oxide, however the scarcity and high expenses greatly hinder their large-scale application. The objective of this thesis is to develop high efficiency and low cost nanomaterials as an alternative to noble metal based electrocatalysts for OER.
Chapter one surveys the background of OER and the development of OER catalysts. In chapter two, carbon black-supported nickel sulfide-derived nanoparticles (NiS/CB(st)-DNs) were developed as electrocatalysts for OER under alkaline condition. The carbon black-supported nickel sulfide (NiS/CB(st)) were synthesized via a one-step solvothermal method. The surface of nickel sulfide is converted into nickel oxide under OER conditions which is mainly responsible for the long-time OER activity. After sufficiently optimizing the parameters of synthesis process, the optimal NiS/CB(st)-DNs can catalyze OER to achieve a current density of 10 mA cm
-2 with an overpotential of 277 mV for over 20 h in alkaline condition (1.0 M KOH), with a corresponding Tafel slope of 72 mV dec
-1.
In chapter three, investigation of doping heteroatom into NiS to further enhance the OER activity was made, including iron, cobalt, manganese, and copper. And the OER activity of NiS was mostly enhanced by doping iron. The iron doped nickel sulfide (Fe-NiS) with an irregular morphology was facilely synthesized via a similar solvothermal method. Under the OER conditions, the surface of Fe-NiS is mainly converted into metal oxides and these derived nanoparticles are responsible for the long-time catalytic activity toward OER. The optimal Fe-NiS-DNs exhibit excellent catalytic activity and strong stability for OER in alkaline condition (1.0 M KOH), only requiring an overpotential of 216 mV to achieve a current density of 10 mA cm
-2 for over 10 h, with a corresponding Tafel slope of 46 mV dec
-1. This result is comparable
with precious IrO
2 and RuO
2 catalysts, and the state-of-the-art non-noble catalysts in recent reports. We ascribe the excellent activity of the Fe-NiS-DNs catalyst to Fe incorporation, interaction between the surface metal oxides and the inner sulfides, metallic electrical conductivity of nickel sulfide, and the hierarchically porous structure.
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