Co-utilization of wastewater sludge and heavy metals for single-atom electrocatalytic reduction of gaseous CO.

Synergetic management of waste activated sludge, heavy metals (HMs) and CO for their valorization and cyclic utilization is rarely reported. Herein, we employed sludge-derived extracellular polymeric substances (EPS) and HMs in wastewater to fabricate a gas diffusion electrode (GDE) for electrochemical CO reduction. This approach atomically dispersed Ni at each nanofiber of the GDE. Abundant N element in the EPS proved to play a key role in the formation of N-Ni (mixture of N-Ni and N-Ni) sites for highly efficient CO to CO conversion. The atomical Ni shows high catalytic activity. Direct gaseous CO reduction in a membrane electrode assembly generated a current density up to 50 mA·cm with CO:H ratio of ∼100 and ∼75% FE under 2.69 cell voltage. This strategy takes advantage of all waste streams generated on site and consolidates traditionally separated treatment processes to save costs, produces value-added products and generates carbon benefits during wastewater treatment.