Abstract
Developing the optimized electrocatalysts with high Pt utilization as well as the outstanding performance for the oxygen reduction reaction (ORR) has raised great attention. Herein, the effects of the interlayer ZrC, HfC, or TiN and the multilayer Pt shell on the adsorption ability and the catalytic activity of the TiC@Pt core-shell structures are systemically investigated by density functional theory (DFT) calculations. For the sandwich structures, the presence of TiN significantly enhances the adsorption ability of the Pt shell, leading to the deterioration of the activity whilst the negligible influence of the ZrC and HfC insertion results the comparable performance with respect to TiC@Pt1ML. In addition, increasing the thickness of the Pt shell reduces the oxyphilic capacity and then mitigates the OH poisoning. From the free energy plots, the superior activity of TiC@Pt2ML is identified in comparison with 1ML and 3ML Pt shell. Herein, the improved activity with its high Pt atomic utilization makes the potential TiC@Pt2ML electrocatalyst for the future fuel cells.
Highlights
Proton exchange membrane fuel cells (PEMFC) have attracted widespread attention due to their high efficient and zero carbon emission for the hydrogen economy [1,2,3,4]
It as previously revealed that when transition metal (TM) elements acted as the core, such as Pd [9,10], Ru [11], or Ir [12], the oxygen reduction reaction (ORR) activity of the corresponding TM@Pt core-shell was enhanced compared with the commercial Pt/C
Gibbs free energy changes (∆G) of the ORR elemental steps have been calculated according to the computational hydrogen electrode (CHE) model developed by Nørskov et al where the chemical potential of proton/electron (H+ + e− ) in solution is equal to the half of the chemical potential of a gas-phase H2 [5]
Summary
Proton exchange membrane fuel cells (PEMFC) have attracted widespread attention due to their high efficient and zero carbon emission for the hydrogen economy [1,2,3,4]. It as previously revealed that when transition metal (TM) elements acted as the core, such as Pd [9,10], Ru [11], or Ir [12], the ORR activity of the corresponding TM@Pt core-shell was enhanced compared with the commercial Pt/C. Such a TM core would not be suitable from an economic aspect [13]. The core-shell structure consisting of the TiC core and the Pt shell acting as the ORR cathode could be the solution for the future requirements of the PEMFC cathode material. The data provides the fundamental understanding of relationship between the activity of TiC@Pt core-shell materials and the interlayer or the shell thickness and further identify the optimal candidate to guide the experimental progress for top-down material design
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