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

Abstract

The electrochemical reduction of nitrite (NO₂⁻) to ammonia (NH₃) under mild conditions (NO₂RR) not only removes excess NO₂⁻ pollutants from groundwater but also enables sustainable recycling of nitrogen resources. The development and design of electrocatalysts that can efficiently produce NH₃ 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 intrinsic NO₂RR activity to prepare a PMo₁₀V₂/Co@NC/CNT composite electrocatalyst. Herein, the cobalt nanoparticles serve as adsorption and activation sites for NO₂⁻, while the PMo₁₀V₂ 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 NH₃ could reach 97.09%, with a yield of up to 0.1342 mmol h⁻¹ mg_cat⁻¹. When assembled into a Zn–NO₂⁻ battery using PMo₁₀V₂/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 NO₂RR electrocatalysts, but also offers a valuable reference for the application of nanomaterial–cluster composites in nitrogen cycle management and sustainable energy conversion.