Bifunctional electroreduction catalysts of NiFe alloy on N-doped carbon toward industrial-level CO2 conversion powered by Zn-air batteries

We present a facile pyrolysis method for the synthesis of nitrogen-doped carbon-supported NiFe alloys (NiFe-NC) that exhibit excellent electrocatalytic activity for both the CO2 reduction reaction (CO2RR) and the oxygen reduction reaction (ORR). Notably, the NiFe-NC catalyst demonstrates an unprecedented CO2RR activity with a CO faradaic efficiency (FE) of 93.42% at -0.58 V vs. RHE. In addition, NiFe-NC in a flow cell reactor achieves an industrial current density of 241.09 mA cm(-2) with a high CO FE of 91.6%. Furthermore, the NiFe-NC catalyst shows an impressive ORR performance, with an onset potential of 0.967 V vs. RHE and a half-wave potential of 0.867 V vs. RHE, which is comparable to that of commercial Pt/C catalysts. We demonstrate the potential of NiFe-NC as a cathode material in Zn-air batteries (ZABs), achieving a maximum power density of 185.92 mW cm(-2). Importantly, a self-driven CO2 flow electrolysis system powered by two series-connected NiFe-NC-based ZABs is designed. This innovative system demonstrates high efficiency in converting CO2 to CO, with a continuous operation time of up to 27 h. According to theoretical calculations, the NiFe-NC catalyst contains Ni-ApyNH and Fe-GN sites, which exhibit remarkable activity in ORR and CO2RR, respectively. The superior bifunctional electrocatalytic performance of NiFe-NC makes it a promising candidate for a wide range of applications. We anticipate that the results of our approach and the exploration of the exact active site of the catalyst will stimulate further studies on the development of efficient electrocatalysts for energy conversion and storage.

Automated summary

We demonstrated a facile pyrolysis method for synthesizing nitrogen-doped carbon-supported NiFe alloys (NiFe-NC) that exhibit excellent electrocatalytic activity for both CO2 reduction reaction (CO2RR) and oxygen reduction reaction (ORR). The NiFe-NC catalyst showed unprecedented CO2RR activity with a high CO faradaic efficiency and achieved a industrial current density and CO FE comparable to commercial catalysts for CO2RR. It also demonstrated impressive ORR performance comparable to commercial Pt/C catalysts. Moreover, the NiFe-NC was successfully used as a cathode material in Zn-air batteries and showed high power density. A self-driven CO2 flow electrolysis system powered by two series-connected NiFe-NC-based Zn-air batteries was designed and showed high efficiency in converting CO2 to CO. The results of this study provide insights for the development of efficient electrocatalysts for energy conversion and storage.