# Coupling of Engineered High Entropy Alloys with Semiconducting TiO2 Nanofilms for Scalable and Ultrafast Alkaline Hydrogen Evolution Reaction

## TL;DR

Researchers developed a scalable method to create efficient hydrogen-producing catalysts by combining high-entropy alloys with titanium dioxide nanofilms, achieving excellent performance under light and heat.

## Contribution

A new scalable fabrication method for hybrid photoelectrocatalysts combining HEAs and TiO2 nanofilms is introduced.

## Key findings

- The hybrid photoelectrocatalysts achieved an ultralow overpotential of –11 mV at 10 mA cm−2 under illumination and elevated temperature.
- TiO2 nanofilms act as a dynamic electron-buffering layer, enhancing charge transfer and active site availability.
- The HER process involves three stages with structural and electronic evolution of TiO2.

## Abstract

High entropy alloys (HEAs) are a promising class of electrocatalysts because of their high reactivity. However, the development of scalable synthesis strategies and fundamental understanding of their interfacial synergy with metal oxides remains underexplored. Herein, a new approach is reported for the fabrication of hybrid photoelectrocatalysts combining PtFeCoNiCu HEA structures with titanium dioxide (TiO2) nanofilms via sequential anodization and electrodeposition. The TiO2 nanofilms function as both a photoactive semiconducting framework and nanostructured substrate, enabling controlled nucleation and growth of HEA nanoparticles through a Volmer–Weber mechanism. The resulting hybrid photoelectrocatalysts exhibit outstanding hydrogen evolution reaction (HER) performance, achieving an ultralow overpotential of –11 mV at 10 mA cm−2 under simultaneous illumination and elevated electrolyte temperature. Mechanistic studies combining in situ Raman spectroscopy and density functional theory simulations reveal that HER occurs through three distinct stages, during which the TiO2 support undergoes dynamic structural and electronic evolution – from a passive scaffold to an electron‐buffering layer. This process involves Ti⁴⁺ reduction, hydrogen intercalation, and accelerated turnover of OH* intermediates, which collectively enhance interfacial charge transfer and broaden active‐site availability. These findings provide new insights into the dynamic interplay between HEAs–semiconducting metal oxide substrates, enabling a generalizable design strategy for scalable, high‐performance photoelectrocatalysts.

A facile and scalable strategy is presented to fabricate high‐performance hybrid photoelectrocatalysts combining PtFeCoNiCu HEA and TiO2–NFs via sequential anodization and electrodeposition, achieving an ultralow overpotential of –11 mV at η10 and excellent thermal stability.