Spherical Murray-Type Assembly of Co-N-C Nanoparticles as a High-Performance Trifunctional Electrocatalyst.

Abstract

Future renewable energy conversion requires advanced electrocatalysis technologies for hydrogen production, fuel cells, and metal-air batteries. Highly efficient trifunctional nonprecious electrocatalysts are a critical precious metal replacement for the economically viable electrocatalysis of oxygen reduction and water splitting, both of which are a triphase electrode process. Electrocatalysts with a refined porous structure and active composition beneficial for three-phase reactions are broadly pursued. Herein, a highly promising trifunctional spherical Murray assembly of Co-N-C nanoparticles was derived from low-cost Prussian blue analogues for the oxygen reduction reaction and water splitting. The Murray-type architecture with a tunable porous hierarchy for efficient mass transfer and the combination of a Co-N-C active composition are key for the improved electrocatalytic performance. Acid-leaching produced an optimized Murray-type durable and methanol-tolerant Co-N-C electrocatalyst that achieved an onset potential of 0.94 V [vs reversible hydrogen electrode (RHE)] and a half wave potential of 0.84 V (vs RHE) as well as a large diffusion-limited current density of 5.7 mA cm-2 for the oxygen reduction reaction, which is comparable to Pt/C. In addition, it displayed low onset overpotentials of ∼150 and ∼350 mV corresponding to the hydrogen evolution reaction and oxygen evolution reaction, respectively, highlighting its great potential to be used in overall water splitting with a total splitting voltage of 1.73 V. This work highlights the importance of Murray-type electrocatalysts for multiphase energy-related reactions.