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Abstract Many ligands commonly used to prepare nanoparticle catalysts with precise nanoscale features contain nitrogen (e.g., oleylamine); here, it is found that the use of nitrogen‐containing ligands during the synthesis of metal oxide nanoparticle catalysts substantially impacts product analysis during photocatalytic studies. These experimental results are confirmed via hybrid Density Functional Theory (DFT) 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. 

Abstract Electrochemical nitrate reduction reaction (NO₃RR) has garnered increasing attention as a pathway for converting a harmful pollutant (nitrate) into a value‐added product (ammonia). However, high selectivity toward ammonia (NH₃) is imperative for process viability. Optimizing proton availability near the catalyst is important for achieving selective NH₃production. Here, the aim is to systematically examine the impacts of proton availability on NO₃RR selectivity in a bipolar membrane (BPM)‐based membrane electrode assembly (MEA) system. The BPM generates a proton flux from the membrane toward the catalyst during electrolysis. Thus, the BPM‐MEA system can modulate the proton flux during operation. The impact of interposer layers, proton scavenging electrolytes (CO₃²⁻), and catalyst configurations are also examined to identify which local microenvironments favor ammonia formation. It is found that a moderate proton supply allows for an increase in ammonia yield by 576% when compared to the standard MEA setup. This also results in a high selectivity of 26 (NH₃over NO₂⁻) at an applied current density of 200 mA cm⁻².