Electronic structure modulation of molybdenum-iron double-atom catalyst for bifunctional oxygen electrochemistry

Abstract

Exploration of cost effective and high performance electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is becoming the paramount interest towards the emerging renewable energy technologies such as fuel cells, metal air-batteries and water electrolysers, etc. One of such catalysts is single atom catalyst that exhibits well defined active sites with very high atom utilization efficiency but selective mainly towards ORR. We demonstrate one-step synthesis of carbon–nitrogen (CN)-coordinated Fe-Mo double atom catalyst with high atom utilization efficiency towards both ORR and OER. The catalyst exhibits enhanced activity with lower overpotential associated with ORR and OER (ΔE = Ej=10(OER) - E1/2(ORR)) and better mass activity in comparison to that of Mo-N-C and Fe-N-C, even better than the state-of-the-art Pt/C and RuO2 catalysts for ORR and OER, respectively. This place the double atom catalysts in the series of non-precious metal based bifunctional catalysts for overall oxygen electrochemistry and is due to the electronic structure modification around the metal atoms induced by other neighbouring metal atom. The double atom Fe-Mo-N-C exhibits a remarkable and highly durable ORR performance with suppressed peroxide generation due to the muted outer sphere electron transfer mechanism in comparison with the commercially available state-of-the-art Pt/C electrocatalyst. Moreover, Fe-Mo-N-C shows remarkable enhanced overall oxygen electrochemistry at higher temperature (323 K - a temperature 25 K above the room temperature), widening its applicability. Overall, this work paves the way to design multi-atom catalysts towards multi-functional electrocatalytic activities.