PtCo on continuous-phase graphene as PEM fuel cell catalyst

For the first time, graphene grown by chemical vapor deposition (CVD) process is utilized as catalyst support following transfer onto polymer electrolyte membrane (M) or gas diffusion layer (GDL) as continuous-phase. Thus, agglomeration and stacking of graphene sheets due to van der Waals forces are minimized. The main purpose of this study is investigation of PtCo atomic ratio on continuous-phase graphene for PEM fuel cell. Eight different ratios of Pt (IV) and Co (II) salts are reduced on CVD grown graphene (G) sheet at room temperature using sodium borohydride to obtain varying PtCo nanoparticle compositions. Electrode activity increases with increasing atomic ratio of PtCo up to 1:3 both on membrane and gas diffusion layer for anode with the highest power densities of 1085 mW cm⁻² (1:3-PtCo/G-M) and 1630 m W cm⁻² (1:3-PtCo/G-GDL). For cathode, on the other hand, the highest performances are obtained with 1:2 PtCo/G-M (355 mW cm⁻² at 0.5 V) and 1:1 PtCo/G-GDL (515 mW cm⁻² at 0.5 V) compositions. The results show that the enhanced electrocatalytic activity is obtained at critical atomic ratio of Pt and Co due to changes in Pt-Pt distances, d-electron vacancy and adsorption. Continuous-phase of graphene causes mass transfer limitations at the cathode effecting water removal at high current densities.