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

Abstract

Three anodic electrocatalysts containing Ni–Pt core–shell (C_Ni–S_Pt), Ni–Pd core–shell (C_Ni–S_Pd) and Ni–Ru core–shell (C_Ni–S_Ru) 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 C_Ni–S_Pt/rGO, C_Ni–S_Pd/rGO and C_Ni–S_Ru/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 C_Ni–S_Pd/rGO exhibited the highest current density for borohydride oxidation (39 085 A g⁻¹) compared to C_Ni–S_Pt/rGO (30 790 A g⁻¹) and C_Ni–S_Ru/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 C_Ni–S_Pd/rGO as a suitable electrocatalyst. This system enhanced the power generation by 32.57% and 80.98% in comparison with that of C_Ni–S_Pt/rGO (233.98 mW cm⁻²) and C_Ni–S_Ru/rGO (171.40 mW cm⁻²), respectively. Thus, this study revealed that C_Ni–S_Pd/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.