Hierarchical Porous Carbon-PtPd Catalysts and Their Activity toward Oxygen Reduction Reaction

Exploring the Role of the Connection Length of Screen-Printed Electrodes towards the Hydrogen and Oxygen Evolution Reactions

Zero-emission hydrogen and oxygen production are critical for the UK to reach net-zero greenhouse gasses by 2050. Electrochemical techniques such as water splitting (electrolysis) coupled with renewables energy can provide a unique approach to achieving zero emissions. Many studies exploring electrocatalysts need to "electrically wire" to their material to measure their performance, which usually involves immobilization upon a solid electrode. We demonstrate that significant differences in the calculated onset potential for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be observed when using screen-printed electrodes (SPEs) of differing connection lengths which are immobilized with a range of electrocatalysts. This can lead to false improvements in the reported performance of different electrocatalysts and poor comparisons between the literature. Through the use of electrochemical impedance spectroscopy, uncompensated ohmic resistance can be overcome providing more accurate Tafel analysis.

Improved Oxygen Reduction on GC-Supported Large-Sized Pt Nanoparticles by the Addition of Pd

PdPt bimetallic nanoparticles on carbon-based supports functioning as advanced electrode materials have attracted attention due to their low content of noble metals and high catalytic activity for fuel cell reactions. Glassy carbon (GC)-supported Pt and PdPt nanoparticles, as promising catalysts for the oxygen reduction reaction (ORR), were prepared by the electrochemical deposition of Pt and the subsequent spontaneous deposition of Pd. The obtained electrodes were examined using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), and electroanalytical techniques. An XPS analysis of the PdPt/GC with the highest ORR performance revealed that the stoichiometric ratio of Pd: Pt was 1:2, and that both Pt and Pd were partially oxidized. AFM images of PdPt2/GC showed the full coverage of GC with PdPt nanoparticles with sizes from 100–300 nm. The ORR activity of PdPt2/GC in an acid solution approached that of polycrystalline Pt (E1/2 = 0.825 V vs. RHE), while exceeding it in an alkaline solution (E1/2 = 0.841 V vs. RHE). The origin of the improved ORR on PdPt2/GC in an alkaline solution is ascribed to the presence of a higher amount of adsorbed OH species originating from both PtOH and PdOH that facilitated the 4e-reaction pathway.