Electrocatalytic Deuterated Nitric Acid Reduction to Deuterated Ammonia.

Electrocatalytic nitrate (NO3 -) deuteration reaction (ENDR) offers a sustainable route for the distributed synthesis of deuterated ammonia (ND3). Present studies focus on alkaline electrolytes, which suffer from excessive cell voltage due to the high D2O dissociation energy. The deuterated nitric acid (DNO3) solution can supply an abundant D3O+ source and be easily formed via NOx direct absorption in pure D2O. However, the acidic condition inevitably triggers the competing deuterium evolution reaction (DER) and severe electrocatalyst deactivation. Herein, we design and construct low-coordinate Rh nanoclusters anchored on mesoporous carbon spheres (Rh NCs/MCS), which exhibits an outstanding long-term ENDR stability over 200 h with a Faradaic Efficiency exceeding 80% in pure DNO3. A series of characterizations reveal that low-coordinate structure enhances the adsorption of *NO2, while the MCS could accumulate nitrite and decrease D3O+ concentration near Rh active sites. The dual-positive effects could boost the ND4 + selectivity and inhibit the competing DER. Furthermore, a high ND4 + yield (6.15 mmol h-1) at industrial current densities (240 mA cm-2) is achieved in a scaled-up electrolytic system. This work establishes a new paradigm for distributed ND3 synthesis and provides a universal principle for designing robust acidic electrocatalysts.