# Constructing an S-Scheme NiO/SrTiO3 Heterojunction for Highly Enhanced Visible-Light Photocatalytic Removal of Methylene Blue

## TL;DR

A new photocatalyst, NiO/SrTiO3, efficiently removes methylene blue from water using visible light, offering a sustainable solution for industrial dye pollution.

## Contribution

The study introduces an S-scheme NiO/SrTiO3 p-n heterojunction with enhanced visible-light photocatalytic performance and a proposed charge-transfer mechanism.

## Key findings

- The optimal NiO (10%)/SrTiO3 sample completely degrades methylene blue within 9 minutes.
- The apparent rate constant is 34.6 times higher than pure SrTiO3.
- The S-scheme mechanism promotes carrier separation and maintains high redox capability.

## Abstract

Organic dye pollution in industrial wastewater poses a serious environmental challenge, with methylene blue (MB) serving as a typical persistent pollutant due to its stable chemical structure, recalcitrance to degradation, and eco-toxicity. Conventional physical, chemical, and biological treatment methods suffer from limitations such as insufficient efficiency, high cost, or the tendency to generate secondary pollution. Based on green and sustainable photocatalysis technology, this study designed and prepared a NiO/SrTiO3 p-n heterojunction photocatalysts, aiming to broaden the light-response range and enhance charge-carrier separation efficiency. The optimal sample (NiO (10%)/SrTiO3) achieved complete photocatalytic degradation of MB within 9 min, with an apparent rate constant 34.6 times that of pure SrTiO3. It also showed good cyclic stability. Trapping experiments confirmed that •OH and •O2− were the key active species in the degradation process. Combined with band structure and PL analyses, an S-scheme charge-transfer mechanism was proposed, clarifying the critical role of the built-in electric field at the heterojunction interface in promoting carrier separation while maintaining high redox capability. This work not only provides a new pathway for developing efficient and stable SrTiO3-based photocatalysts but also offers theoretical and experimental support for the practical application of p-n heterojunction photocatalysts in environmental pollution control.