Skeletal Density Measurements for Adsorbent Nanomaterials

TL;DR

This study measures skeletal densities of various adsorbent nanomaterials using helium pycnometry and discusses how these measurements influence the accuracy of hydrogen adsorption calculations and related engineering metrics.

Contribution

It provides new skeletal density data for diverse adsorbent materials and analyzes their impact on hydrogen adsorption measurements.

Findings

Skeletal densities ranged from 2.02 to 2.23 g/cm³ for tested materials.

Underestimating skeletal density by 10% can cause at least 5-7% errors in hydrogen adsorption calculations.

Skeletal density significantly influences the accuracy of storage capacity assessments.

Abstract

Due to their tunable material properties, sorptive materials have a wide range of applications in energy storage, water treatment, carbon capture, analytical chemistry, and more. One crucial factor in determining the effectiveness of such materials is their skeletal density, or "true density" because it is often used to calculate key metrics, such as storage capacities. In this paper, we present skeletal density measurements through helium pycnometry for several types of adsorbent carbon materials derived from either corncob, sawdust, coffee grounds, polyvinylidene chloride (PVDC), graphitic carbon nitride (GCN), or metal organic frameworks (MOFs). The measured skeletal density of sawdust-based activated carbon was 2.02 +/- 0.05 g/$cm^{ 3}$. The measured skeletal density of coffee-based activated carbon was 2.23 +/- 0.06 $cm^{ 3}$. We also expound upon the impact that skeletal density has upon hydrogen excess adsorption measurements and other calculated engineering quantities. If a skeletal density is underestimated by 10%, it can affect the room temperature excess adsorption by at least 5% at 100 bar and by 7% at 200 bar, depending on the material type.