Efficient Electrocatalytic Conversion of Nitrate in Water with Anderson-Type Polyoxometalate-Modified Co-MOF

The electrochemical conversion of nitrate to ammonia has garnered growing attention, as it aims to reduce carbon emissions and promote environmental sustainability. Nevertheless, developing an electrocatalyst that exhibits outstanding activity, selectivity, and stability is still a significant challenge. Here, we report three Anderson-type polyoxometalates (POMs)-modified cobalt metal-organic framework (Co-MOF), namely, Co-MOF/MMo₆ (M = Fe, Co, Ni) composite electrocatalyst, fabricated using an easy standing method. Among them, POMs not only facilitated the formation of lamellar structures with a high specific surface area of Co-MOF as a morphology regulator but also contributed to electron transfer between Co-MOF as an electron-rich cluster, achieving an enhancement in the catalytic performance of NO₃RR to NH₃. In particular, Co-MOF/NiMo₆ exhibits NO₃RR performance with maximal Faradaic efficiency of 98.2% at -0.8 V vs the reverse hydrogen electrode (vs reversible hydrogen electrode (RHE)) and NH₃ yield rate of up to 10.88 mg h^-1 mg_cat.^-1, better than most previously reported MOF-based catalysts. By in situ spectrometric measurement, we demonstrate that the NH₃ formation via a kinetically favored pathway of NO₃^- → *NO₃ → *NO₂ → *NO → *NH₂OH → *NH₃. This work indicates the considerable potential of POM-based MOF materials for the electrochemical NO₃RR to NH₃.