Particle-in-box nanostructured materials created via spatially confined pyrolysis as high performance bifunctional catalysts for electrochemical overall water splitting

Abstract

Novel particle-in-box nanostructure was developed and demonstrated as a high performance bifunctional catalyst for electrochemical overall water splitting. The particle-in-box nanostructure was composed of N-doped graphene layer coated Fe-Ni alloy nanoparticles encapsulated within an N-doped carbon hollow nanobox. The nanobox serves as a nanoreactor with the reactant, water, and catalyst nanoparticles confined within for intimate contact and effective reaction. The particle-in-box nanostructure was created through a spatially confined pyrolysis process by taking polydopamine coated Ni3[Fe(CN)6]2·H2O nanocubes as the precursor, calcination of which leading to formation of an N-doped porous carbon shell from the carbonization of the polydopamine coating layer and formation of interior N-doped graphene layer coated Fe-Ni alloy nanoparticles from reduction of both iron and nickel ions and graphitization of the CN groups. The particle-in-box nanostructured catalyst exhibited excellent electrocatalytic activities, achieving overpotentials of 270 and 201 mV for the oxygen and hydrogen evolution reactions, respectively at 10 mA/cm2, and thus is suitable of serving as a high performance bifunctional catalyst for the overall water splitting reaction, achieving a low full cell overpotential of 471 mV at 10 mA/cm2. The excellent electrocatalytic activity may be attributed to the advantageous particle-in-box nanostructure offering confined and effective reaction environment and the synergistic effects resulting from the conductive, hollow, and porous carbon shell and the small size of the Fe-Ni alloy nanoparticle core and its N-doped graphene layer shell. This new nanostructure of particle-in-box is superior and advantageous for a wide range of applications, not only for electrocatalytical reactions but also for other heterogeneous reaction systems.