1. Chromium-Doped Transition Metal Oxyhydroxide Catalysts for Electrochemical Water Oxidation
- Author
-
Bo, Xin
- Subjects
- Operando Analysis, Oxygen Evolution Reaction, Oxyhydroxide
- Abstract
Hydrogen gas (H2) has been considered as one of the most promising energy carriers for its high energy density (283 KJ•mol-1) and clean combustion product (H2O). Electrochemical water splitting is one of the most efficient approaches to produce hydrogen. However, the anodic oxygen evolution reaction (OER) involves a sluggish four-electron process, which heavily impedes the industrial application. Therefore, it is of great challenge to design the high-active OER catalysts with lower cost. In this thesis, we developed a series of Cr containing nonprecious-metal-based hydroxide materials as advanced OER catalysts and investigated the synergistic effect and regulation effect on the intrinsic OER catalysis and crystallization process, respectively. (i) The ternary NiFeCr hydroxide electrode with nanoporous sheet structure has been achieved via facile electrodeposition method and demonstrates enhanced OER catalytic performance over the benchmark NiFe hydroxide electrode. (ii) Then spectroelectrochemical operando Raman and X-ray absorption spectroscopy (XAS) reveal the synergistic effect from Cr incorporation that Cr and Fe substitute for the Ni’s lattice position in pristine Ni(OH)2 phase, which in turn is converted into the active Cr, Fe-substituted-β-NiOOH intermediate with the valence states of Cr6+, Fe3+ and Ni2+, whose shorter Cr-O may promote the OER process. (iii) Thereafter, the analogous catalyst of CoFeCr hydroxide is also developed and shows the improved OER catalytic performance as well, due to the similar property of Co to Ni. (iv) Last, the regulation effect from the Cr on crystallization and phase homogenization of NiFe, CoFe oxide/hydroxides is also investigated to reveal that Cr significantly induces the multi-phase with large particle size into homogeneously amorphous nanodots with the sharply size reduction to 2~3 nm, and the obtained amorphous Cr incorporated Ni(Co)Fe nanodots also demonstrate enhanced OER performance, which is attributed to the enlarged surface area and formation of active intermediates during reaction. This thesis fundamentally investigates the trimetallic oxyhydroxide compounds containing Cr and contributes to the rational design of advanced OER catalysts with enhanced catalytic activity.
- Published
- 2020