Metal-encapsulated nitrogen-doped carbon nanotube arrays electrode for enhancing sulfion oxidation reaction and hydrogen evolution reaction by regulating of intermediate adsorption

For treatment of sulfion-containing wastewater, coupling the electrochemical sulfion oxidation reaction (SOR) with hydrogen evolution reaction (HER) can be an ideal way for sulfur and H2 resources recovery. Herein, we synthesize a metal-modified carbon nanotube arrays electrode (Co@N-CNTs/CC) for SOR and HER. This electrode has excellent performance for SOR and HER attributed to the unique array structure. It can achieve 99.36 mA/cm2 at 0.6 V for SOR, and 10 mA/cm2 at 0.067 V for HER. Density functional theory calculations verify that metal modification is able to regulate the electronic structure of carbon nanotube, which is able to optimize the adsorption of intermediates. Employed Co@N-CNTs/CC as bifunctional electrodes to establish a hybrid electrolytic cell can reduce about 67% of energy consumption compared with the traditional water splitting electrolytic cell. Finally, the hybrid electrolytic cell is used to treat actual sulfion-containing wastewater, achieving the sulfur yield of 30 mg h−1 cm−2 and the hydrogen production of 0.64 mL/min.