Interplay between Nitrogen Concentration, Structure, Morphology, and Electrochemical Performance of PdCoNi “Core–Shell” Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

Abstract

This report describes the electrochemical behavior of a family of “core‐shell” electrocatalysts consisting of a carbon nitride (CN) “shell” matrix and a “core” of conducting carbon nanoparticles (NPs). The CN “shell” matrix embeds PdCoNi alloy NPs and covers homogeneously the carbon “core”. The chemical composition of the materials is determined by inductively‐coupled plasma atomic emission spectroscopy (ICP‐AES) and microanalysis; the structure is studied by powder X‐ray diffraction (powder XRD); the morphology is investigated by high‐resolution transmission electron microscopy (HR‐TEM). The surface activity and structure are probed by CO stripping. The oxygen reduction reaction (ORR) kinetics, reaction mechanism, and tolerance towards contamination from chloride anions are evaluated by cyclic voltammetry with the thin‐film rotating ring‐disk electrode (CV‐TF‐RRDE) method. The effect of N concentration in the matrix (which forms “coordination nests” for the Pd‐based alloy NPs bearing the active sites) on the ORR performance of the electrocatalysts is described. Results show that N atoms: 1) influence the evolution of the structure of the materials during the preparation processes, and 2) interact with alloy NPs, affecting the bifunctional and electronic ORR mechanisms of active sites and the adsorption/desorption processes of oxygen molecules and contaminants. Finally, the best PdCoNi electrocatalyst shows a higher surface activity in the ORR at 0.9 V vs. RHE with respect to the Pt‐based reference (388 μA cmPd‐2 vs. 153 μA cmPt‐2).

Origins, Developments, and Perspectives of Carbon Nitride-Based Electrocatalysts for Application in Low-Temperature FCs

“…ECs. Pd-trimetallic "core-shell" ECs show an ORR performance which increases as: (a) T f is raised; and (b) the N concentration in the "shell" decreases 5,35,36 (see Fig. 4).…”

Graphitic Carbon Nitride Materials for Energy Applications

“…Various graphitized carbon support materials with special pore structures have also been explored, such as carbon nanotubes (CNT), nanofibers (CNF), nanohorns (CNH) and nanocoils, all showing promising results, although the costly and complex synthesis methods employed constitute a barrier to their introduction into market (34)(35)(36)(37)(38)(39)(40). The introduction of nitrogen into carbon supports has showed to improve durability, as well as enhancing the intrinsic catalytic activity for both oxygen reduction (ORR) and methanol oxidation (MOR) reactions (41)(42)(43)(44)(45)(46)(47)(48). The N-dopant has been reported to alter the catalyst electronic structure, resulting in a higher binding energy, which may decrease the specific interaction between the Pt nanoparticles and potential poisoning intermediates (49).…”

Highly active and durable Pd nanoparticles-porous graphitic carbon nitride composite for electrocatalytic oxygen reduction reaction

“…Therefore, the ORR activity in presence of methanol on Ptesurface is reduced drastically. V.D.Noto and co-workers recently demonstrated [40] that the N-based ligand in CN x matrix easily prevent the adsorption of the poising molecules such as methanol during the ORR performance. The Pd-CN x composite exhibited very good tolerance towards methanol oxidation is probably due to presence of large number of nitrogen in CN x support.…”