Advanced Electrocatalysts for Water Splitting
高效電解水電化學催化劑
Student thesis: Doctoral Thesis
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Detail(s)
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| Award date | 17 Sept 2024 |
Link(s)
| Permanent Link | https://scholars.cityu.edu.hk/en/theses/theses(df5f8619-a7c5-4849-9c84-1d77ffdd0a2d).html |
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| Other link(s) | Links |
Abstract
Electrochemical water splitting is a promising approach for sustainable energy production since it can convert energy from intermittent and renewable sources such as sunlight into hydrogen and oxygen. The water splitting contains two half reactions: the hydrogen evolution reaction (HER) at cathode, and the oxygen evolution reaction (OER) at anode. Both reactions require efficient electrocatalysts in order to promote the overall water splitting into industrially applicable level, especially the kinetically sluggish OER process. Therefore, to develop advanced electrocatalysts for HER and OER is in great demand. This thesis introduces three projects that aim at developing novel, sustainable, and efficient electrocatalysts for HER and OER.
Chapter one introduced the background and recent developments of the electrocatalysts for water splitting. In chapter two, firstly we synthesized iron doped-nickel sulfide (FeNiS) nanoparticles as electrocatalysts for OER in alkaline conditions, that delivered a current density of 10 mA cm-2 with an overpotential of 242 mV. Then we studied the influence of doping high oxidation state metals into FeNiS on the catalytic activity of OER, and we found that doping molybdenum (FeNiMoS) can effectively promote the OER activity, that only need 190 mV to deliver a current density of 10 mA cm-2.
In chapter three, we developed a novel method to synthesize nanoclusters with two metallic elements at merely 1~2 nm. Guided by the studies of HER mechanisms, we assume the bimetallic nanoclusters can favor the HER to follow Volmer-Tafel approach. With this strategy, several types of nanoclusters supported by carbon with different metal combinations were synthesized and applied for HER, including RuPt, NiPt, PtPt, and PtIr. Among these, the RuPt on carbon (RuPt@CB) demonstrated exceptionally high metal mass activity and excellent stability. In acidic conditions, the RuPt@CB catalyst showed 2 and 28.4 A mg-1Me at the overpotentials of 20 and 80 mV, respectively, 28.5 and 20.3 times higher than that of the commercial Pt/C, surpassing most state-of-the-art noble metal-based catalysts for HER. The synergetic effect between Ru and Pt triggers the Volmer-Tafel mechanism and contributes to the fast kinetics of HER.
In chapter four, we investigated a much challenging project, electrocatalysts for OER in acidic conditions. Traditional OER catalysts such as metal oxides are highly unstable in acid, and the reaction kinetics of OER in acid is more sluggish than that in alkaline. In this work, we found that bonding Ir to Ru can effectively prevent Ru from being dissolved in acid, which greatly enhanced the stability of Ru-based catalysts in acid OER. Moreover, RuIr nanoclusters supported by monolayer MoS2 showed stronger stability than RuIr without MoS2. After a series of optimization, the MoS2RuIr only required an overpotential of 179 mV to deliver a current density of 10 mA cm-2, with strong stability over 80 h in acidic conditions.
In chapter five, we gave a summary and future perspectives based on the studies of this thesis.
Chapter one introduced the background and recent developments of the electrocatalysts for water splitting. In chapter two, firstly we synthesized iron doped-nickel sulfide (FeNiS) nanoparticles as electrocatalysts for OER in alkaline conditions, that delivered a current density of 10 mA cm-2 with an overpotential of 242 mV. Then we studied the influence of doping high oxidation state metals into FeNiS on the catalytic activity of OER, and we found that doping molybdenum (FeNiMoS) can effectively promote the OER activity, that only need 190 mV to deliver a current density of 10 mA cm-2.
In chapter three, we developed a novel method to synthesize nanoclusters with two metallic elements at merely 1~2 nm. Guided by the studies of HER mechanisms, we assume the bimetallic nanoclusters can favor the HER to follow Volmer-Tafel approach. With this strategy, several types of nanoclusters supported by carbon with different metal combinations were synthesized and applied for HER, including RuPt, NiPt, PtPt, and PtIr. Among these, the RuPt on carbon (RuPt@CB) demonstrated exceptionally high metal mass activity and excellent stability. In acidic conditions, the RuPt@CB catalyst showed 2 and 28.4 A mg-1Me at the overpotentials of 20 and 80 mV, respectively, 28.5 and 20.3 times higher than that of the commercial Pt/C, surpassing most state-of-the-art noble metal-based catalysts for HER. The synergetic effect between Ru and Pt triggers the Volmer-Tafel mechanism and contributes to the fast kinetics of HER.
In chapter four, we investigated a much challenging project, electrocatalysts for OER in acidic conditions. Traditional OER catalysts such as metal oxides are highly unstable in acid, and the reaction kinetics of OER in acid is more sluggish than that in alkaline. In this work, we found that bonding Ir to Ru can effectively prevent Ru from being dissolved in acid, which greatly enhanced the stability of Ru-based catalysts in acid OER. Moreover, RuIr nanoclusters supported by monolayer MoS2 showed stronger stability than RuIr without MoS2. After a series of optimization, the MoS2RuIr only required an overpotential of 179 mV to deliver a current density of 10 mA cm-2, with strong stability over 80 h in acidic conditions.
In chapter five, we gave a summary and future perspectives based on the studies of this thesis.
