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Enhancing volumetric power density (VPD), for fuel cell vehicles or combined heat and power systems, has always been a determined desired goal. To give an idea, the present VPD = 5.5 kW L−1 for 2020 Toyota-MIRAI, is targeted to 9.0 kW L−1 by 2040 by Japan. The present research proposes that the conventional GDL + ribbed/channel setup, e.g. in parallel-serpentine (PS) bipolar-plates (BPPs), to be replaced by functionally graded porous material (FGPM) or variable-porosity metal-foam (VPMF) flow distributors. For the present comparative study, at cell current density 1 A/cm2, the fuel cell with FGPM flow-distributor provides over 80% enhancements in VPD, w.r.t. the PS cases. The enhancement is even higher at higher currents densities. The present manuscript contains three parts: (1) development of a novel protocol to design FGPMs for flow distributors. Through several examples, it has been shown that the designed FGPM reduces the flow resistances towards-, and from-the concave corner areas. Hence, flow can reach-to, and leave-from these corners effectively; (2) application of the noted FGPM protocol to fuel cells, in which a three-dimensional and two-phase computational fluid dynamics model has been used to compare the performances of the FGPM flow-distributors with conventional channel/ribbed PS cases; and finally (3) guidelines are proposed on how to manufacture the FGPM flow-distributor. The present model opens a new era in designing flow-distributors for FCs and can be applied to both graphite and metallic BPPs. [Display omitted] • Novel Functionally Graded Porous Material (FGPM) flow-distributor is designed for fuel cells (FC). • FGPM provides uniform flow velocity at each section from inlet-to-exit including the corners. • FGPM improves volumetric power density through volume reduction and power increase. • FC with FGPM flow distributor gives over 80% enhancements w.r.t. parallel-serpentine FC. • Manufacturing of FGPM or Variable Porosity Metal-Foam (VPMF) is described. [ABSTRACT FROM AUTHOR]