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

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/Nid/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). (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Ni-based catalysts show efficient performance in alkaline hydrogen oxidation and oxygen reduction reactions, with controlled chemical etching of Ni-based MOFDC prior to Pd deposition enhancing catalyst performance. Pd/Ni-d/MOFDC exhibits superior activity in HOR and promises to be an excellent electrocatalyst for alkaline membrane fuel cells.