A Cu–Co 3 O 4 Tandem Catalyst for Efficient Electrocatalytic Nitrate Reduction at Low Concentration

Electrocatalytic reduction of nitrate (NO3−) in the waste streams to valuable ammonia under ambient conditions is a green route for nitrate remediation. However, the efficient catalysts are required for this multi-step proton coupled electron transfer reaction. This work presented a tandem catalyst composed of N-doped carbon layer coated Co3O4 coupled with CuOx as a highly efficient and selective electrocatalyst for NO3− reduction to NH3 at low onset potential. The tandem catalysis of NO3−→NO2−→NH3 over the two synergistical sites of in-situ generated metallic Cu and Co3O4 was verified by experiments and theoretical calculations. Benefiting from the two coupled active sites, the catalyst exhibited an ammonia yield rate of 5.37 mg h−1 cm−2 at −0.4 V versus RHE and a Faradaic efficiency of 92.72 % at an ultralow potential of −0.1 V versus RHE. This work opens a new avenue for the design of highly efficient tandem catalysts for electrocatalytic nitrate reduction.