Enhanced activity of Pd/α-MnO2 for electrocatalytic oxygen evolution reaction

Abstract

This work describes the application of α-MnO2 and Pd/α-MnO2 as electrocatalysts in the oxygen evolution reaction (OER). Characterization data revealed that the Pd2+ precursor has been oxidized during the synthesis, and the resulting Pd4+ ions have unprecedently replaced the lattice framework Mn3+ ions of α-MnO2. Furthermore, formation of PdO nanoparticles was also observed. Lower OER overpotential at j = 10 mA cm−2 (636 mV) was obtained for Pd/α-MnO2 in relation to α-MnO2 (700 mV), what is in alignment with the lower charge transfer resistance of Pd/α-MnO2 (4.9 kΩ cm2) compared to α-MnO2 (10.4 kΩ cm2). Lower Tafel slope (73 mV dec−1) and higher TOF (2.87 × 10−4 s−1) at overpotential of 350 mV was obtained for Pd/α-MnO2 in relation to α-MnO2 (Tafel of 77 mV dec−1 and TOF of 1.94 × 10−4 s−1), indicating a faster electron transfer kinetics promoted by Pd. Pd/α-MnO2 was stable at j = 14 mA cm−2 for 6 h.