Integration of electrocatalysts with silicon microcone arrays for minimization of optical and overpotential losses during sunlight-driven hydrogen evolution

Microstructured photoelectrode morphologies can advantageously facilitate integration of optically absorbing electrocatalysts with semiconducting light absorbers, to maintain low overpotentials for fuel production without producing a substantial loss in photocurrent density. We report herein the use of arrays of antireflective, high-aspect-ratio Si microcones (mu-cones), coupled with light-blocking Pt and Co-P catalysts, as photocathodes for H-2 evolution. Thick (similar to 16 nm) layers of Pt or Co-P deposited onto Si m-cone arrays yielded absolute light-limited photocurrent densities of similar to 32 mA cm(-2), representing a reduction in light-limited photocurrent density of 6% relative to bare Si mu-cone-array photocathodes, while maintaining high fill factors and low overpotentials for H-2 production from 0.50 M H2SO4(aq). The Si mu-cone arrays were embedded in a flexible polymeric membrane and removed from the Si substrate, to yield flexible photocathodes consisting of polymer-embedded arrays of free-standing mu-cones that evolved hydrogen from 0.50 M H2SO4(aq).