# Optical readout of hydrogen storage in films of Au and Pd

## TL;DR

This study investigates optical methods to monitor hydrogen absorption and release in Au and Pd films, revealing how composition and thermal treatment influence sensor performance and hydrogen kinetics.

## Contribution

It introduces a novel optical monitoring approach for hydrogen in Au/Pd films and demonstrates control over hydrogen uptake/release through composition and thermal processing.

## Key findings

- Optical transmission increases in hydrogenated Pd-rich films.
- Hydrogen release is slower than uptake, up to three times.
- Annealed Au:Pd films show faster hydrogen kinetics.

## Abstract

For hydrogen sensor and storage applications, films of Au and Pd were (i) co-sputtered at different rates or (ii) deposited in a sequential layer-by-layer fashion on a cover glass. Peculiarities of hydrogen uptake and release were optically monitored using 1.3 micrometers wavelength light. Increase of optical transmission was observed for hydrogenated Pd-rich films of 10-30 nm thickness. Up to a three times slower hydrogen release took place as compared with the hydrogen uptake. Composition ratio of Au:Pd and thermal treatment of films provided control over the optical extinction changes and hydrogen uptake/release time constants. Higher uptake and release rates were observed in the annealed Au:Pd films as compared to those deposited at room temperature and were faster for the Au-richer films. Three main parameters relevant for sensors: sensitivity, selectivity, stability (reproducibility) are discussed together with the hydrogenation mechanism in Au:Pd alloys.