Strong Electronic Interaction between Amorphous MnO₂ Nanosheets and Ultrafine Pd Nanoparticles toward Enhanced Oxygen Reduction and Ethylene Glycol Oxidation Reactions

Abstract

Strengthening the interface interaction between metal and support is an efficient strategy to improve the intrinsic activity and reduce the amount of noble metal. Amorphization of support is an effective approach for enhancing the metal‐support interaction due to the numerous surface defects in amorphous structure. In this work, a Pd/a‐MnO2 electrocatalyst containing ultrafine and well‐dispersive Pd nanoparticles and amorphous MnO2 nanosheets is successfully synthesized via a simple and rapid wet chemical method. Differing from the crystal counterpart (Pd/c‐MnO2), the flexible structure of amorphous support can be more favorable to electron transfer and further enhance the metal‐support interaction. The synergism between Pd and amorphous MnO2 results in the downshift of the d‐band center, which is beneficial for the desorption of critical intermediates both in oxygen reduction reaction (ORR) and in ethylene glycol oxidation (EGOR). Due to the lower *.OH desorption energy of Pd/a‐MnO2 surface, the rapid dissociation of *OH from Pd facilitates the formation of H2O in ORR, thus demonstrating superior ORR performance comparable to Pt/C. For EGOR, the presence of amorphous MnO2 promotes the formation of adsorbed OH species, which accelerates the desorption of intermediate CO from Pd sites, and thus exhibits excellent EGOR activity and stability.

Synthesis of MnOOH and its application in a supporting hexagonal Pd/C catalyst for the oxygen reduction reaction

“…Referring to the JADE PDF standard card (Pd 05-0681), the (111) crystal face with the highest diffraction peak intensity is consistent with the calculated Pd crystal face spacing of 0.225 nm, so it can be proved that the hexagonal crystal in the HRTEM image is crystal Pd nanparticles. [48][49][50] By observing Fig. 3g, it can be seen that there is a large crystal in the lower right corner of the image that is different from the crystal lattice stripe of Pd.…”

B-Doping-Induced Lattice Expansion of Pd Metallene Nanoribbons for Oxygen Reduction Reaction

“…Such electronic structure modulation lowers the d-band center in B-Pd MNRs, thereby decreasing the adsorption energy of ORR intermediates and accelerating the desorption of oxygen-containing species. 14,35,45 Additionally, the B 1s spectrum of B-Pd MNRs can be employed to further identify the interaction between B and Pd. As displayed in Figure 3d, the binding energies of 187.…”

“…Notably, the Pd 3d peaks of B-Pd MNRs exhibit a positive shift in comparison to those of Pd MNRs, suggesting that B-doping modulates the electronic structure of Pd. Such electronic structure modulation lowers the d -band center in B-Pd MNRs, thereby decreasing the adsorption energy of ORR intermediates and accelerating the desorption of oxygen-containing species. ,, Additionally, the B 1s spectrum of B-Pd MNRs can be employed to further identify the interaction between B and Pd. As displayed in Figure d, the binding energies of 187.35 and 190.97 eV can be attributed to the metallic B and oxidized boron species, respectively. , This result indicates that B-doping may optimize the adsorption of O 2 molecules on B-Pd MNRs .…”

Recent Progress of Amorphous Nanomaterials

“…As was mentioned earlier, the amorphous support can contribute to faster electron transfer compared with the corresponding crystalline nanosheets because the structural flexibility can strengthen the metal–support interaction. To that end, Hu et al synthesized well-dispersed Pd nanoparticles anchored on amorphous MnO 2 nanosheets (Pd/a-MnO 2 ) using a simple and rapid wet-chemical method (Figure a–d) . Pd/a-MnO 2 can be successfully prepared by a rapid two-step wet-chemical strategy.…”

“…(o) HAADF-TEM image and corresponding EDS mapping of elements Cr, Ni, and O. (a–d) are adapted with permission from ref . Copyright 2023, Wiley.…”