Urea sits at the intersection of food security and hard-to-abate chemistry. Produced at the megaton scale via fossil-fed Haber–Bosch and the Bosch–Meiser processes, its manufacture is tightly coupled to CO₂ emissions and centralized infrastructure. Against this backdrop, Electrochemical Urea Synthesis (EUS) has been proposed as a way to electrify both carbon and nitrogen management. The basic concept goes way back: in 1995 Shibata and co-workers reported urea formation from the coreduction of CO₂ and nitrate/nitrite on Cu-based gas diffusion electrodes¹, but only in the last few years the topic has grown into a fast-expanding research field.

The resulting literature, however, rests on a fragile foundation, flanked by urea detection and quantification issues^2–4. In a recent Viewpoint⁵, we argued that EUS lies at the crossroad between two problematic areas: CO₂ reduction tested in batch H-cells at low current density, and nitrogen electrochemistry hampered by false positives and weak analytical practice. Widely used urea quantification protocols—urease/indophenol blue, DAMO–TSC colorimetry, and ¹H NMR—are each prone to specific artefacts, from nitrite interference to time-dependent color evolution and detection limits misaligned with realistic production rates. At the same time, many EUS studies employ non-scalable cell designs and weakly buffered electrolytes, where pH drift and mass-transport limitations decouple reported metrics from any industrially relevant scenario.

Our own work on EUS began in October 2022, when experiments deliberately inspired by Shibata’s conditions appeared to indicate promising urea formation on copper. This observation triggered a systematic effort to understand whether we were truly synthesizing urea, or simply probing the limits of our analytical tools. Building on our initial “UREAlity Check”⁵, we developed an HPLC/UV–vis method to separate and quantify urea in typical EUS electrolytes, and re-examined modified DAMO–TSC protocols with nitrite suppression⁶. Together, these tools improved sensitivity while exposing how easily common procedures can misreport urea in complex matrices.

With this toolbox in place, we revisited CO₂ + NO₃^- coreduction on polycrystalline Cu—the first EUS-active catalyst ever reported—in both H-cells and a three-compartment flow cell, using near-neutral KHCO₃ + KNO₃ electrolytes. Extensive chronopotentiometry across relevant current densities and potential windows yielded rich product distributions in CO₂ reduction and nitrate reduction, but no HPLC-detectable urea. Only trace signals appeared in modified colorimetric assays, at levels incompatible with the high Faradaic efficiencies reported in the 1990s.

This experience also reshaped our perspective on where the field should go next. It is now evident that improving analytics, while necessary, is not sufficient. Cell and process engineering—gas-fed architectures, membrane and electrolyte choice, pH management and buffering, current density, and single-pass conversion—are as central to the credibility of an EUS claim as the catalyst itself. At the same time, emerging oxidative EUS routes, in which urea is formed by coupling CO with NH₃ at the anode rather than by co-reducing CO₂ and nitrate at the cathode, remind us that EUS spans distinct chemistries and device concepts.

In this contribution, I will place urea synthesis in its historical and industrial context, discuss the availability and sustainability of carbon and nitrogen feedstock, and examine how cell configuration and electrolyte engineering govern both performance and data reliability. I will then draw on our own results to outline practical guidelines for rigorous urea detection and for benchmarking both reductive and oxidative EUS pathways when assessing their prospects as viable technologies.