Carbon nanotubes embedded with NiS nanocrystals outperform Pt in dye-sensitized solar cells: interface improved activity

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 7; no. 17; pp. 145 - 1411
• Main Authors: Wang, Xiuwen, Xie, Ying, Jiao, Yanqing, Pan, Kai, Bateer, Buhe, Wu, Jun, Fu, Honggang
• Format: Journal Article
• Language: English
• Published: 24.04.2019
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta00649d

Designing a Pt-free counter electrode (CE) electrocatalyst with superior catalytic activity for triiodide (I 3 − ) reduction and electrochemical stability for dye-sensitized solar cells (DSSCs) is always challenging. An active-site-enriched NiS/multiwalled carbon nanotube (CNT) composite was synthesized using small-sized NiS nanoparticles in situ embedded in CNTs through the hot-injection method. A DSSC fabricated with the NiS/CNT CE exhibited an excellent activity to I 3 − reduction with a surprising photoelectric conversion efficiency (PCE) of 10.82%, outperforming Pt (8.03%). The superior catalytic activity and stability of NiS/CNTs were also observed from electrochemical characterization. DFT calculations revealed that this satisfactory activity was mainly attributed to the appropriate binding energy of I 3 − on the Ni atoms of the embedded NiS at the unique NiS-CNT interface. Moreover, the strong bonding in the NiS and CNT interface with reduced work function facilitated electron delocalization from embedded NiS nanoparticles to the C walls of CNTs, where the charge-transfer ability was improved. Thus, the as-synthesized NiS/CNT composite is a promising CE material to replace the expensive Pt electrocatalyst in DSSCs. An active-site-enriched NiS/CNT composite with a unique interface was synthesized and exhibited a surprising photoelectric conversion efficiency of 10.82%.