Dinitrogen Reduction Coupled with Methanol Oxidation for Low Overpotential Electrochemical NH3 Synthesis Over Cobalt Pyrophosphate as Bifunctional Catalyst

Electrochemical dinitrogen (N2) reduction to ammonia (NH3) coupled with methanol electro‐oxidation is presented in the current work. Here, methanol oxidation reaction (MOR) is proposed as an alternative anode reaction to oxygen evolution reaction (OER) to accomplish electrons‐induced reduction of N2 to NH3 at cathode and oxidation of methanol at anode in alkaline media thereby reducing the overall cell voltage for ammonia production. Cobalt pyrophosphate micro‐flowers assembled by nanosheets are synthesized via a surfactant‐assisted sonochemical approach. By virtue of structural and morphological advantages, the maximum Faradaic efficiency of 43.37% and NH3 yield rate of 159.6 µg h−1 mgca−1 is achieved at a potential of −0.2 V versus RHE. The proposed catalyst is shown to also exhibit a very high activity (100 mA mg−1 at 1.48 V), durability (2 h) and production of value‐added formic acid at anode (2.78 µmol h−1 mgcat−1 and F.E. of 59.2%). The overall NH3 synthesis is achieved at a reduced cell voltage of 1.6 V (200 mV less than NRR‐OER coupled NH3 synthesis) when OER at anode is replaced with MOR and a high NH3 yield rate of 95.2 µg h−1 mgcat−1 and HCOOH formation rate of 2.53 µmol h−1 mg−1 are witnessed under full‐cell conditions. Application of CoPPi catalyst as a bifunctional catalyst towards electrochemical dinitrogen (N2) reduction to ammonia (NH3) coupled with methanol electro‐oxidation by replacing anodic oxygen evolution reaction to reduce the cell voltage during NH3 synthesis.