Nitrogen-containing Surface Ligands Lead to False Positives for Photofixation of N$_2$ on Metal Oxide Nanocrystals: An Experimental and Theoretical Study

TL;DR

Nitrogen-containing ligands used in nanoparticle catalyst synthesis can cause false positives in photocatalytic nitrogen fixation studies, emphasizing the need for careful synthetic protocol design and contamination detection.

Contribution

This study reveals how nitrogen ligands interfere with photocatalytic nitrogen reduction measurements and demonstrates the importance of synthetic pathway design to avoid contamination.

Findings

Nitrogen ligands cause false positives in photocatalytic N2 fixation tests.

Hybrid DFT confirms ligand contamination impacts electronic properties.

Careful synthesis can prevent ligand-induced false results.

Abstract

Many ligands commonly used to prepare nanoparticle catalysts with precise nanoscale features contain nitrogen (e.g., oleylamine); here, we found that the use of nitrogen-containing ligands during the synthesis of metal oxide nanoparticle catalysts substantially impacted product analysis during photocatalytic studies. We confirmed these experimental results via hybrid Density Functional Theory computations of the materials' electronic properties to evaluate their viability as photocatalysts for nitrogen reduction. This nitrogen ligand contamination, and subsequent interference in photocatalytic studies, is avoidable through the careful design of synthetic pathways that exclude nitrogen-containing constituents. This result highlights the urgent need for careful evaluation of catalyst synthesis protocols, as contamination by nitrogen-containing ligands may go unnoticed since the presence of nitrogen is often not detected or probed.