Yb/Ho co-doping and rGO bridging enhance visible-to-NIR-light-driven photocatalysis in an S-scheme heterojunction

Abstract

The limited light absorption range and rapid recombination rate of photogenerated electron–hole pairs are significant challenges hindering the practical implementation of semiconductor photocatalytic technology. This study proposed a strategy of rare earth metal ion co-doping and rGO bridging in S-scheme heterojunctions to simultaneously improve light absorption capability and charge separation rate. The up-conversion property (UCP) of Yb and Ho expands the light absorption range of Yb and Ho co-doped NiFe LDH/rGO/In₂S₃ (YH-NF/rGO/IS), while rGO plays a dual role by serving as an electron bridge to enhance charge separation and as a growth surface for YH-NF and IS to expose active sites. Combined results from KPFM, in situ XPS and DFT calculations confirm the formation of an S-scheme heterojunction between YH-NF and IS. The verified built-in electric field, directed from IS to YH-NF, drives the efficient separation and transfer of photogenerated charge carriers. Under near-infrared (NIR) light for 60 min, YH-NF/rGO/IS exhibits an enhanced photocatalytic degradation rate of o-nitrophenol (ONP) at 86.9 ± 1.0%, which is notably higher than that of YH-NF (35.9 ± 2.4%). The rate constant surpasses that of YH-NF and IS by 17.3 and 16.1 times, respectively. Furthermore, YH-NF/rGO/IS effectively resists interference from coexisting ions and demonstrates good stability, retaining a 93% degradation efficiency after five cycles, indicating promising application potential. The degradation pathway of ONP was analyzed and the intermediates show reduced toxicity. This research provides insights for designing new and highly efficient vis-NIR photocatalysts.