# Life Cycle Assessment and Critical Raw Materials Analysis of Innovative Palladium-Substituted Membranes for Hydrogen Separation

## TL;DR

This study evaluates sustainable alternatives to palladium in hydrogen separation membranes using environmental and material criticality analyses.

## Contribution

The paper introduces a novel framework combining LCA and criticality analysis for evaluating lab-scale membrane sustainability.

## Key findings

- Higher palladium content in membranes correlates with greater environmental impacts.
- Vanadium-palladium (VPd) membranes show 65-71% lower environmental impacts than PdAg membranes.
- Monte Carlo simulations confirmed the robustness of the LCA model with data uncertainties.

## Abstract

Palladium-based membranes for hydrogen separation offer the most promising gas permeation and selectivity, but their large-scale application has been limited due to the high environmental burdens and criticality of palladium. Herein, the possibility of substituting Pd with candidate elements in the composition of metallic micro-scale membranes (with permeability in the range of 5–50 × 10−12 mol m–1 Pa–1 s−1) deposited via High Power Impulse Magnetron Sputtering was investigated. This study proposed an innovative framework for a more comprehensive investigation of the sustainability challenges related to this lab-scale technology by integrating Life Cycle Assessment (LCA) and criticality analyses, thereby supporting materials selection efforts. First, the criticality status of several elements used in hydrogen separation membranes was screened with two different approaches. Furthermore, the environmental impacts of novel membrane compositions were compared with a high Pd-content reference membrane (Pd77Ag23) through cradle-to-gate LCA. For robust LCA modeling, uncertainty analysis was performed via Monte Carlo simulation, exploiting errors estimated for both primary and secondary data. A direct relationship was identified between the Pd content in membranes and the associated environmental impacts. VPd proved to be a promising candidate by exhibiting lower total impacts than the PdAg (65% or 71% considering thickness of 3.16 µm or permeance of 2.03 × 10−6 mol m−2 Pa−1 s−1, respectively).