Structurally optimized intrinsic defect carbon driven polysulfide reduction reaction for quantum dot sensitized solar cells

Abstract

Typically, the more intrinsic defects of carbon materials are unfavorable to conductivity, while they are considered to be the active sites of carbon materials in the field of electrocatalysis. Therefore, seeking a balance between conductivity and active sites is the key to improve the catalytic performance of unadulterated carbon materials. Herein, the hierarchical porous carbon (HPC) prepared by the soft-templating approach is accurately adjusted via the facile hydrothermal method using H₃BO₃ and H₃PO₃ as structural modulators. The structural characterization indicates that both H₃BO₃ and H₃PO₃ reagents can drive the carbon catalyst to produce more intrinsic defects, and H₃PO₃ can reduce the amount of oxygen-containing groups in the carbon surface to improve conductivity. The structurally optimized HPC used as a counter electrode in polysulfide electrolytes exhibits a charge transfer resistance as low as 2.25 Ω, and the CdS/CdSe quantum dot sensitized solar cell (QDSSC) has a power conversion efficiency of 4.62%. These confirm that the reduction activity towards S_n²⁻ ions in QDSSCs can be effectively improved by adjusting the degree of carbon defects. This report provides a new perspective on intrinsic defects for improving the electrocatalytic activity of the unadulterated carbon material.