Non-noble metal single atom catalysts for electrochemical energy conversion reactions

Non-noble metal single atom catalysts (NNMSACs) are being pursued as economical alternatives to noble-metal SACs while retaining the high catalytic activity derived from the unique electronic structure of the single atomic sites. NNMSACs can serve crucial roles in various electrocatalytic reactions with high atomic utilization efficiency and selectivity comparable to noble metal SACs via adequate metal-support interactions. To this end, this review summarizes the characteristics of NNMSACs with regard to tuning reaction selectivity, metal-support interaction, and catalytic active center. Subsequently, an extensive summary of representative NNMSACs (Co, Ni, Fe, Cu, and dual metal SACs) is introduced for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR). Finally, we present a brief conclusion and the remaining challenges for further advances of NNMSACs in geometric, electronic, and electrochemical properties.