UCLA

Electrochemical processes play a central role in clean energy generation, storage, and utilization. The rapid development of fuel cells that can efficiently convert chemical fuels to electricity will significantly reduce fossil fuel combustion to enable a sustainable future. Besides, water electrolysis is an essential environmentally friendly technique for the future hydrogen economy and vehicle market. The efficiency of these electrochemical processes relies on the rational design of high-performing electrocatalysts, which requires an atomic-level understanding of the charge/mass transfer and chemical transformation at the surface and interface of the electrocatalysts. The extent to which nanostructuring produces high performing surface and interface for efficient energy transformation is likely to cover a wide range of metal/metal alloys, transition metal oxides, sulfides, and nitrides, and is currently the focus of intensive research. To date, noble metal platinum (Pt) has been proved to be the most active element to catalyze most of the electrochemical reactions required in the fuel cells and water electrolyzers. Due to the high cost of Pt and the high energy consumption resulted from the inevitable overpotential of those electrochemical reactions, optimizing the specific activity (SA), mass activity (MA), and the overpotential presents the key challenges for the design of commercial electrochemical catalysts. This requires the systematic and controllable surface/interface engineering of the Pt catalysts for the rapid electron and mass transfer. The first part of my dissertation presents how the single-atom nickel-modified Pt nanowires (SANi-PtNWs) with abundant activated Pt sites next to the SANi and minimal blockage of the surface Pt sites can be synthesized using a partial electrochemical dealloying approach. This single atom tailoring strategy ensures the optimal combination of SA and ECSA to deliver the highest mass activity and durability for diverse electrochemical reactions. In the second part of the dissertation, we will introduce the direct synthesis of single-atom Rh tailored Pt nanowires (SARh-PtNWs) with optimum surface oxophilicity for the hydrogen oxidation reaction. The optimal surface oxophilicity on the SARh Pt nanowires surface ensures the optimum OHads/H2O↓ adsorption on the single-atom Rh sites at 0 V vs. RHE, which facilitates the removal of Hads and hence accelerates the total hydrogen oxidation rate by over one magnitude compared to that of Pt. Apart from the single-atom tailoring strategy, in the third part, we will discuss a unique surface decoration of the Pt-tetrapod framework with water-permeable amorphous Ni(OH)2 shell. Such decoration will keep the Pt sites covered from accessing the reactant such as water, proton, and hydroxyl, and thus can boost the MA and SA simultaneously.