Rational design of highly efficient electrocatalysts using atomic layer deposition: from nanoparticle to single atom
Abstract
Polymer electrolyte membrane fuel cells (PEMFCs) have been attracted significant attention due to their high energy efficiency. The electrocatalyst is one of the most important parts. However, state-of-the-art electrocatalysts suffer from several challenges, including 1) low stability under harsh working conditions; 2) low atomic utilization efficiency, especially for noble metals. This thesis, therefore, focuses on the design of highly efficient and stable electrocatalysts from nanoparticles down to single atoms using atomic layer deposition (ALD) and further understand the insight mechanisms.
Firstly, Pt nanoparticles are selectively deposited on the TiO2 modified N-doped carbon nanotubes. The strong metal-support interactions between Pt and TiO2 enhances both the catalytic activity and stability in the oxygen reduction reaction (ORR).
Further, to promote the electronic property of the surface Pt, a surface engineering strategy using Nb single atoms has been developed. The deposition of Nb single atoms is found to promote both the activity and stability of Pt catalysts in the ORR.
Furthermore, to achieve the maximum atomic utilization efficiency, a high-loading Pt single-atom catalyst (SAC) is successfully achieved using N-doped carbon nanosheets as support. The nature of Pt1 atoms under electrochemical hydrogen evolution reaction (HER) is investigated using operando X-ray absorption spectroscopy (XAS).
Finally, the Fe, Co, and Ni SACs are achieved using the pre-located Pt single atoms. The Co and Ni SACs are found to be active in the HER and oxygen evolution reaction, respectively. Moreover, the nature of several types of single atoms under HER is investigated using operando XAS.
In summary, the discoveries in this thesis provide important guidance to achieve electrocatalysts with low cost, high activity, and high stability.