Cobalt nanoparticles coupled with polyoxometalate nanoclusters to boost electrocatalytic conversion of nitrite to ammonia at low potential

The electrochemical reduction of nitrite (NO 2 -) to ammonia (NH 3 ) under mild conditions (NO 2 RR) not only removes excess NO 2 -pollutants from groundwater but also enables sustainable recycling of nitrogen resources. The development and design of electrocatalysts that can efficiently produce NH 3 at relatively low potentials has become one of the bottleneck issues in this electrochemical conversion process. In light of this, this work innovatively coupled polyoxometalate nanoclusters with strong electron reservoir capacity and cobalt nanoparticles with good NO 2 RR intrinsic activity to prepare PMo 10 V 2 /Co@NC/CNTs composite electrocatalyst. Herein, the cobalt nanoparticles serve as adsorption and activation sites for NO 2 -, while the PMo 10 V 2 clusters act as electron transfer promoters. The experimental results showed that at a relatively low potential of -0.3 V (vs. RHE), the Faradaic efficiency of NH 3 could reach 97.09%, with a yield of up to 0.1342 mmol h -¹ mg cat -¹. When assembled into a Zn-NO 2 -battery using PMo 10 V 2 /Co@NC/CNTs as the cathode, a power density of 4.1 mW cm -2 was achieved. This study not only provides new insights into the design of high-efficiency cobalt-based NO 2 RR electrocatalysts, but also offers a valuable reference for the application of nanomaterial-cluster composites in nitrogen cycle management and sustainable energy conversion.