Hydrogen oxidation and oxygen reduction reactions on palladium nano-electrocatalyst supported on nickel-deficient MOF-derived carbons

• Published in: Electrochimica acta 2021-09, Vol.390, p.138860, Article 138860
• Main Authors: Ipadeola, Adewale K., Mwonga, Patrick V., Ozoemena, Kenneth I.
• Format: Article
• Language: English
• Subjects: Catalysts; Chemical analysis; Chemical etching; Chemical reactions; Density functional theory; Diffusion coefficient; Diffusion rate; Diffusivity; Electrocatalysts; Exchange current density; Fuel cells; Highly active Pd/Ni-d/MOFDC catalyst; Mass activity; Ni-deficient MOF-derived carbon; Nickel; Oxidation; Oxygen reduction reactions; Palladium
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2021.138860

•Pd catalyst with Ni-deficient composite (Pd/Ni-d/MOFDC) has endowed physico-chemistry for excellent HOR and ORR kinetics.•The enhanced performance of Pd/Ni-d/MOFDC is related to the advantageous effects of defect chemistry.•DFT calculations corroborate the influence of Ni-deficient supports rather than its high content.•Pd/Ni-d/MOFDC is a promising electrocatalyst for alkaline membrane fuel cells. Pd/Ni-based catalysts consisting of Ni-rich MOF-derived carbon (Pd/Ni-r/MOFDC) and Ni-deficient counterpart (Pd/Ni-d/MOFDC) have been demonstrated as efficient nanostructured catalysts for alkaline hydrogen oxidation (HOR) and oxygen reduction reactions (ORR). Physico-chemical analysis of the catalysts unravels the significance of controlled chemical etching of the Ni-based MOFDC prior to deposition of Pd catalyst, thereby controlling the level of Ni(OH)2 interface and defects or oxygen vacancies. The Pd/Ni-d/MOFDC exhibits excellent performance towards HOR compared to the Pd/Ni-r/MOFDC in respects of decreased onset potential (Eonset), but increased exchange current density (jo.s), heterogeneous rate constant (k0), kinetic current (jK), diffusion coefficient (D) and mass activity (jo.m). The more facile HOR performance on Pd/Ni-d/MOFDC corroborates its reduced activation energy (EA) by a factor of 1/3. The alkaline HOR follows the Heyrovsky-Volmer and Tafel-Volmer processes on Pd/Ni-r/MOFDC and Pd/Ni-d/MOFDC, accordingly, evident by their Tafel slope (ba) values. The Pd/Ni-d/MOFDC equally shows improved ORR activity compared to the Pd/Ni-r/MOFDC. Density functional theory (DFT) calculations agree with the experimental data, especially the contributory effects of the chemically etched composite support. Pd/Ni-d/MOFDC promises to be a viable electrocatalyst for the development of alkaline membrane fuel cells (AMFCs). [Display omitted]