Covalent immobilization of ruthenium polypyridyl complex on multi-walled carbon nanotube supports for oxygen evolution reaction in an alkaline solution

Abstract

Electrocatalytic water splitting to realize the sustainable production of hydrogen is one of the key ways to gain renewable clean energy. The development of the ruthenium-terpyridine-bipyridine (bpyRutpy) complexes used as efficient homogeneous water oxidation catalysts is one of the currently hot research fields. All catalytic active sites of the homogeneous molecular catalyst are fully utilized, and show a high catalytic efficiency. However, the homogeneous molecular catalyst has some intrinsic shortages such as difficulty on separation, recovery and regeneration, and high cost. In view of this, we synthesized the multi-walled carbon nanotube (MWCNT)-based heterogeneous catalyst, MWCNT-bpyRutpy, by covalently bonding the ruthenium-based complex onto the carbon nanotubes, in order to achieve the maximum molecular catalytic efficiency of the complex. The synthesized catalyst is fully characterized by mass spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy, ultraviolet–visible spectroscopy, photoelectron spectroscopy, Raman spectroscopy, and thermogravimetry. The formation of the nanocatalyst via fusing Ruthenium complexes to MWCNTs promotes the oxygen evolution reaction (OER) kinetics, enhances intrinsic activity, and increases the specific surface area of electrochemical activity, and achieve excellent OER performance with a low overpotential of 436 mV at 10mAcm2, a low Tafel slope of 77.2 mV, and a relatively high turnover frequency (TOF) of 0.5833 s−1 at an overpotential of 400 mV.