P-doped NiS2/Ni nanoheteroparticles embedded into N-doped carbon framework anchored on multi-walled carbon nanotubes as an efficient counter electrode for Pt-free dye-sensitized solar cells

Abstract

Designing of inexpensive counter electrode (CE) material with robust electrochemical properties and perfect electrical conductivity is of great essential to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Herein, the catalytic nickel nanoparticles are in-situ embedded into nitrogen-doped carbon framework (Ni-NC) by high-temperature carbonization. Next, the formed Ni-NC hybrid is subjected to simultaneous sulfurization/phosphorization treatment in the N2 atmosphere to acquire P–NiS2/Ni-NC. Finally, the acquired P–NiS2/Ni-NC hybrid is anchored on functional carboxylated multi-walled carbon nanotubes (MWCNTs) by ultrasonication to obtain P–NiS2/Ni-NC@MWCNTs. According to the electrochemical results, the P–NiS₂/Ni-NC@MWCNTs CE displays remarkable catalytic activities, great electron transfer ability, and high stability in the iodine/iodide electrolyte. DSSC assembled with P–NiS2/Ni-NC@MWCNTs CE yields an impressive PCE of 9.57 %, surpassing those of platinum (Pt) electrode (PCE = 7.84 %) and other corresponding counterparts. Such notable photovoltaic performance can be ascribed to the structural advantages and synergistic coupling effect of NiS2/Ni nanoheterostructure, P doping effect, and the support role of porous carbon network, which offer abundant catalytic active sites, high porosity, and exceptional electrical conductivity. Our work suggests a novel strategy to fabricate Pt-like CE materials based on transition metal sulfides/carbon-based nanostructures with excellent performances for large-scale energy conversion devices to reach the consumer market.