Boosting the performance of formic acid microfluidic fuel cell: Oxygen annealing enhanced Pd@graphene electrocatalyst

•Oxygen-annealing treatment for Pd@graphene electrocatalyst is developed.•Both electro-oxidation reactivity and CO tolerance are significantly improved.•85% increase in fuel cell power density is achieved after annealing.•The enhancement is attributed to the PdO bond formation.

A new oxygen-annealing treatment for Pd supported on graphene was employed to enhance the electro-catalytic performance in formic acid microfluidic fuel cells. Experiments show that both the electro-oxidation reactivity and CO tolerance of the annealed catalyst are significantly improved. When testing the fuel cell, the maximum power density with annealed catalyst is 41% higher than the unannealed Pd@graphene catalyst, and 85% higher than Pd@Vulcan XC-72. This enhancement is attributed to the PdO bond formation during the oxygen annealing step, which induces greater CO electro-oxidation reactivity.