Alkaline water-splitting reactions over Pd/Co-MOF-derived carbon obtained via microwave-assisted synthesis. Issue 29 (5th May 2020)

• Record Type: Journal Article
• Authors: Ipadeola, Adewale K.; Ozoemena, Kenneth I.
• Is Part Of: RSC advances. Volume 10:Issue 29(2020)
• Page Start: 17359
• Page End: 17368
• Publication Date: 2020-05-05
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0ra02307h
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Palladium nanoparticles supported on MOF-derived carbon serve as an efficient bifunctional electrocatalyst for alkaline water-splitting reactions. Abstract : Cobalt-based metal–organic framework-derived carbon (MOFDC) has been studied as a new carbon-based support for a Pd catalyst for electrochemical water-splitting; i.e., the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline medium. The study shows a high increase in the HER activity, in terms of low onset overpotential (onset η = 35 mV vs. RHE), high exchange current density ( j o, s ≈ 0.22 mA cm −2 ), high mass activity ( j o, m ≈ 59 mA mg −1 ), high kinetic current ( j K ≈ 5–8 mA cm −2 ) and heterogeneous rate constant ( k 0 ≈ 4 × 10 −4 cm s −1 ), which are attributed to the high porosity of MOFDC and contribution from residual Co, while the large Tafel slope ( b c = 261 mV dec −1 ) is ascribed to the high degree of hydrogen adsorption onto polycrystalline Pd as a supplementary reaction step to the suggested Volmer–Heyrovsky mechanism. These values for the catalyst are comparable to or better than many recent reports that adopted nano-carbon materials and/or use bi- or ternary Pd-based electrocatalysts for the HER. The improved HER activity of Pd/MOFDC is associated with the positive impact of MOFDC and residual Co on the Pd catalyst ( i.e., low activation energy, E A ≈ 12 kJ mol −1 ) which allows for easy desorption of the Hads to generate hydrogen. Moreover, Pd/MOFDC displays better OER activity than its analogue, with lower onset η (1.29 V vs. RHE) and b a (≈78 mV dec −1 ), and higher current response ( ca. 18 mA cm −2 ). Indeed, this study provides a new strategy of designing and synthesizing MOFDC with physico-chemical features for Pd-based electrocatalysts that will allow for efficient electrochemical water-splitting processes.