Alkaline water-splitting reactions over Pd/Co-MOF-derived carbon obtained microwave-assisted synthesis.

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; , 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 = 35 mV RHE), high exchange current density ( ≈ 0.22 mA cm), high mass activity ( ≈ 59 mA mg), high kinetic current ( ≈ 5-8 mA cm) and heterogeneous rate constant ( ≈ 4 × 10 cm s), which are attributed to the high porosity of MOFDC and contribution from residual Co, while the large Tafel slope ( = 261 mV dec) 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 (, low activation energy, ≈ 12 kJ mol) which allows for easy desorption of the H to generate hydrogen. Moreover, Pd/MOFDC displays better OER activity than its analogue, with lower onset (1.29 V RHE) and (≈78 mV dec), and higher current response ( 18 mA cm). 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.