In situ construction of Co-CoO heterostructures on rGO-modified nickel foam for high-performance anode catalysts in direct borohydride-hydrogen peroxide fuel cells

Abstract

Direct borohydride hydrogen peroxide fuel cells (DBHPFCs) are emerging as a transformative technology for sustainable energy conversion. Despite their potential, their efficiency is largely hindered by the limitations of the anode catalyst. In response to this challenge, we have developed a novel series of Co-based heterojunction metal–organic framework (MOF) derivatives, supported on reduced graphene oxide (rGO)-modified nickel foam (NF), to enhance borohydride electrooxidation performance. Our synthesis involves the thermal transformation of a ZIF67-Co(OH)₂-rGO/NF precursor within a controlled temperature between 300 and 750 °C, yielding distinct phase heterostructures and pristine Co and CoO, verified by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Additionally, the Ultraviolet photoelectron spectroscopy and theoretical calculation result further validate the formation of the heterojunction and direction of electron transfer along the interface as well as the BH₄⁻ adsorption behavior across the heterointerface. Notably, the catalyst annealed at 600 °C, designated Co-CoO@C-rGO/NF-600, exhibits an exceptional oxidation current density of 2.5 A·cm⁻² at 0 V vs. Ag/AgCl in an electrolyte containing 2 mol·L⁻¹ NaOH and 0.4 mol·L⁻¹ NaBH₄ Furthermore, the Co-CoO@C-rGO/NF-600 catalyst demonstrates remarkable performance as the anode catalyst in a DBHPFC assembly, achieving a peak power density of 385.73 mW·cm⁻² and demonstrating the enduring operational stability. The superior electrocatalytic performance is primarily attributed to the synergistic effects of Co-CoO nanoparticles rich in active heterointerfaces and the superior electron mobility afforded by the rGO scaffold. These results not only deepen our understanding of anode catalyst design for DBHPFCs but also pave the way for breakthroughs in electrocatalytic technologies, driving forward the quest for sustainable energy solutions.