Multi‐Functional Formaldehyde‐Nitrate Batteries for Wastewater Refining, Electricity Generation, and Production of Ammonia and Formate

As bulky pollutants in industrial and agricultural wastewater, nitrate and formaldehyde pose serious threats to the human health and ecosystem. Current purification technologies including chemical and bio-/photo-/electro-chemical methods, are generally high-cost, time-consuming, or energy-intensive. Here, we report a novel formaldehyde-nitrate battery by pairing anodic formaldehyde oxidation with cathodic nitrate reduction, which simultaneously enables wastewater purification, electricity generation, and the production of high-value-added ammonia and formate. As a result, the formaldehyde-nitrate battery remarkably exhibits an open-circuit voltage of 0.75 V, a peak power density of 3.38 mW cm^-2 and the yield rates of 32.7 mg h^-1 cm^-2 for ammonia and 889.4 mg h^-1 cm^-2 for formate. In a large-scale formaldehyde-nitrate battery (25 cm² ), 99.9 % of nitrate and 99.8 % of formaldehyde are removed from simulated industrial wastewater and the electricity of 2.03 W⋅h per day is generated. Moreover, the design of such a multi-functional battery is universally applicable to the coupling of NO₃ ^- or NO₂ ^- reduction with various aldehyde oxidization, paving a new avenue for wastewater purification and chemical manufacturing.