Novel electrocatalysts for borohydride fuel cells: enhanced power generation by optimizing anodic core-shell nanoparticles on reduced graphene oxide

Three anodic electrocatalysts containing Ni-Pt core-shell (CNi-SPt), Ni-Pd core-shell (CNi-SPd) and Ni-Ru core-shell (CNi-SRu) nanoparticles were fabricated on reduced graphene oxide (rGO) via a two-step consecutive reduction process. The rGO-based catalysts were characterized via XRD, FE-SEM, EDAX, TEM, HR-TEM and XPS. The effect of CNi-SPt/rGO, CNi-SPd/rGO and CNi-SRu/rGO toward the borohydride oxidation reaction (BOR) was evaluated in a half-cell and also in a single direct borohydride-hydrogen peroxide fuel cell (DBHPFC). The electrochemical measurements indicated that CNi-SPd/rGO exhibited the highest current density for borohydride oxidation (39-085 A g^-1) compared to CNi-SPt/rGO (30-790 A g^-1) and CNi-SRu/rGO (4563 A g^-1) with the same catalyst loading. The highest power density of 310.20 mW cm^-2 at a current density of 264 mA cm^-2 with 2 M H₂O₂ and 1 M NaBH₄ solution at 60 C was achieved with CNi-SPd/rGO as a suitable electrocatalyst. This system enhanced the power generation by 32.57% and 80.98% in comparison with that of CNi-SPt/rGO (233.98 mW cm^-2) and CNi-SRu/rGO (171.40 mW cm^-2), respectively. Thus, this study revealed that CNi-SPd/rGO is a suitable anodic electrocatalyst for application in DBHPFCs in comparison with the commercially used Pt-based electrocatalysts because of its advantages such as low cost, high activity toward the BOR and stability in fuel cells