Well-defined Nanoparticle Electrocatalysts for Clean Hydrogen Production and Biomass Conversion

The urgent need to mitigate the environmental impact of fossil fuels has led to the development of renewable energy sources. This dissertation focuses on electrochemical strategies for biomass conversion and clean hydrogen production, aiming to minimize the carbon footprint. Two specific reactions are investigated: electrochemical reduction of furfural (FF) and electrochemical splitting of water.
In Chapter 1, a comprehensive review of heterogeneous electrocatalysis for FF reduction and water splitting, including the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is presented. Chapter 2 introduces the experimental setup and characteristic techniques employed throughout this dissertation.
Chapter 3 investigates the enhanced OER activity of the combined Ni3Fe1OOH/TiO2 catalyst compared to single metal catalysts. In situ X-ray absorption spectroscopy (XAS) measurements reveal the formation of a Ni-Fe oxyhydroxide (OOH) species during the OER process, which lead to the good OER activity. The practical implementation of the Ni3Fe1OOH/TiO2 catalyst in an anion exchange membrane electrolyzer (AEMEL) device on Ni foam demonstrates high performance and durability.
In Chapter 4, a novel Pt/Ce2O3/C catalyst is developed for the HER by coupling Pt nanoparticles (NPs) with ultra-thin Ce2O3 nanosheets (NSs) to modify the electronic state of Pt. The Pt/Ce2O3/C catalyst exhibits superior HER activity compared to Pt/C catalyst, attributed to electron transfer from Pt NPs to Ce2O3 NSs, weakening hydrogen adsorption capability. The smaller size of Pt NPs in the Pt/Ce2O3/C catalyst increases surface area and promotes electronic effects between Pt NPs and Ce2O3 NSs, further improving catalytic performance.
Chapter 5 presents a non-iridium-based electrocatalyst, Ni-RuO2, for acidic OER in proton exchange membrane (PEM) water electrolysis. The Ni-RuO2 catalyst exhibits high activity and durability, surpassing pristine RuO2 due to the stabilizing effect of Ni incorporation. The adsorbate evolving mechanism (AEM) over the catalyst during OER is confirmed by differential electrochemical mass spectrometry (DEMS).
Chapter 6 focus on the electrochemical reduction of FF using surface-controlled copper nanocrystals (NCs). The results show that copper nanowires (Cunw) with abundant edges between {100} surface facets and two five {111} strains exhibit higher current density and selectivity towards 2-methylfuran (MF) over furfuryl alcohol (FA), outperforming Cu nanocubes (Cucub) and Cu nanooctahedra (Cuoh). The findings highlight the influence of crystal morphology on electrochemical platform molecule conversion. In Chapter 7, a galvanic replacement mechanism is utilized to synthesize structure-controlled PtSn4 intermetallic nanodisks (PtSn4 NDs) from Sn nanoparticles. The unique crystal structure of PtSn4 NDs demonstrates superior electrocatalytic efficiency for FF reduction, effectively suppressing the competitive HER and exhibiting high faradaic efficiency for FA production.
Overall, this dissertation provides valuable insights into heterogeneous electrocatalysis for clean hydrogen production and biomass conversion. The findings contribute to the development of efficient catalysts and emphasize the importance of interfacial and synergetic effects in enhancing catalytic activity for OER, lowering hydrogen desorption capability of Pt for HER, and targeting MF and FA as the primary products over the facet-depend Cu NCs and structure-dependent PtSn4 NDs, respectively.