# Visible-light photocatalytic oxygen production on a high-entropy oxide by multiple-heterojunction introduction

**Authors:** Parisa Edalati, Yuta Itagoe, Hironori Ishihara, Tatsumi Ishihara, Hoda Emami, Makoto Arita, Masayoshi Fuji, Kaveh Edalati  
**arXiv:** [2301.05016](https://arxiv.org/abs/2301.05016)  
**Date:** 2023-01-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2301.05016v1/

## Key points

- High-entropy oxides (HEOs) are multi-component ceramics with high configurational entropy
- HEOs have attractive properties such as photocatalytic activity for H2 production and CO2 conversion
- Photocatalytic activity of HEOs has been limited to UV light
- Researchers conducted a study on the Ti-Zr-Nb-Ta-W-O system to achieve visible-light-driven photocatalysis
- 10 different heterojunctions were introduced simultaneously using a high-pressure torsion method and oxidation process
- The resulting HEO was able to produce oxygen from water under visible light without a co-catalyst addition
- Factors contributing to this breakthrough include high visible-light absorption, narrow bandgap, appropriate band structure, and multiple heterojunctions facilitating easy separation of electron-hole pairs and minimizing recombination
- High-entropy oxides have potential as new visible-light-active photocatalysts
- Multiple-heterojunction introduction is a strategy for efficient photocatalysis under visible light illumination
- Study provides insights into the design and development of advanced materials for sustainable energy applications in solar-driven water splitting and CO2 conversion.

## Summary

In recent years, there has been a growing interest in high-entropy oxides (HEOs) as multi-component ceramics with high configurational entropy. These materials have shown attractive properties such as photocatalytic activity for hydrogen (H2) production and carbon dioxide (CO2) conversion. However, their photocatalytic activity has been limited to ultraviolet (UV) light. To address this limitation and achieve visible-light-driven photocatalysis, researchers conducted a study on the Ti-Zr-Nb-Ta-W-O system. They introduced 10 different heterojunctions simultaneously in this oxide system using a high-pressure torsion method and oxidation process. Remarkably, the resulting HEO demonstrated the ability to produce oxygen from water under visible light without the need for a co-catalyst addition. This breakthrough in visible-light photocatalysis was attributed to several factors. Firstly, the HEO exhibited high visible-light absorption due to its unique composition and structure. Additionally, it possessed a narrow bandgap and appropriate band structure, enabling efficient utilization of visible light energy. The presence of multiple heterojunctions further facilitated easy separation of electron-hole pairs and minimized recombination, enhancing overall photocatalytic performance. These findings not only highlight the potential of high-entropy oxides as new visible-light-active photocatalysts but also introduce the concept of multiple-heterojunction introduction as a strategy to achieve efficient photocatalysis under visible light illumination. Overall, this study provides valuable insights into the design and development of advanced materials for sustainable energy applications, particularly in the field of solar-driven water splitting and CO2 conversion.