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Using Pd or Pt to achieve propylene electrooxidation is a sustainable electrosynthesis technique to produce oxy-organics. However, the origin behind their potential-dependent product selectivity still remains unclear. Herein, we integrate advanced theoretical methods across grand-canonical ensemble density functional theory (DFT) calculations, Pourbaix analyses, and microkinetic modeling to uncover the completed reaction network of propylene electrooxidation for the first time and found that the electrochemistry-induced reconstructed active center under working potentials, including phase conversion and surface coverage, dominates the potential-dependent selectivity of propylene electrooxidation over Pd and Pt catalysts. With increasing working potential (0.7–1.4 V vs reversible hydrogen electrode, RHE), the active center of the Pd electrode gradually reconstructs from partially O-covered (1/3 ML O*) metallic Pd surface to PdO with partial surface hydroxylation (1/2 ML OH*), and the main product is acrolein at first, then changes to acetone and propylene glycol (PG). On the contrary, the electrochemically reconstructed PtO 2 with partial surface hydroxylation (1/2 ML OH*) is the active center of the Pt electrode under the whole operating conditions (1.2–1.6 V RHE ), and the main products are propylene oxide (PO) and acetone. Our results reproduce the potential-dependent performance of Pd and Pt electrodes from available experiments. In short, this work has clarified the long-standing controversies over the key factors determining propylene electrooxidation products on Pd and Pt, and it reveals the key role of surface reconstruction and active site switching under working potential.
Li et al. (Tue,) studied this question.