Hydrogen oxidation and oxygen reduction reactions on palladium nano-electrocatalyst supported on nickel-deficient MOF-derived carbons. (10th September 2021)

• Record Type: Journal Article
• Authors: Ipadeola, Adewale K.; Mwonga, Patrick V.; Ozoemena, Kenneth I.
• Is Part Of: Electrochimica acta. Volume 390(2021)
• Publication Date: 2021-09-10
• Subjects: Ni-deficient MOF-derived carbon -- Highly active Pd/Ni-d/MOFDC catalyst -- Diffusivity -- Exchange current density -- Mass activity -- Density functional theory; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2021.138860
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: 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. Abstract: 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 ( E onset ), but increased exchange current density ( j o.s ), heterogeneous rate constant ( k 0 ), kinetic current ( j K ), diffusion coefficient ( D ) and mass activity ( j o.m ). The more facile HOR performance on Pd/Ni-d/MOFDC corroborates its reduced activation energy ( E A ) 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 ( b a ) 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). Graphic abstract: Image, graphical abstract