Year: 2026
Type: preprint
Abstract: The photoelectrochemical (PEC) nitrogen reduction reaction (N 2 RR) offers a potentially sustainable route to ammonia (NH 3 ) synthesis. However, reliable evaluation of PEC N 2 RR activity remains challenging due to contamination-induced false positives and competing reactions. Here, we comparatively investigate p -type CuBi 2 O 4 and the previously reported PEC N 2 RR-active photocathode CuO, using an ultra-clean, contamination-controlled measurement system. Despite favorable band energetics and measurable photocurrents, neither material exhibits statistically significant NH 3 production, suggesting that the previously reported activity of CuO most likely originated from contamination-induced false positives rather than genuine N 2 reduction. Density functional theory further shows that the first proton-coupled electron transfer step toward *NNH formation remains kinetically prohibitive, even on oxygen-deficient surfaces, strongly favoring the competing hydrogen evolution reaction (HER). In addition, both photocathodes undergo surface reduction and photocorrosion. Nevertheless, comparative analysis reveals fundamentally different degradation pathways on the two photocathodes. While CuBi 2 O 4 retains its bulk structural integrity under photocathodic conditions, CuO undergoes extensive reduction, restructuring, and dissolution. Together, these findings highlight the importance of contamination control in evaluating aqueous PEC N 2 RR, as well as the challenges of overcoming vigorous competition with HER and photocorrosion processes using Cu(II)-based oxides.
Source: ChemRxiv
Language: English
Subfield: Catalysis
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221177890