Carboxyl-assisted synthesis of Co nanorods with high energy facet on graphene oxide sheets for efficient photocatalytic hydrogen evolution

•High length to diameter ratio Co nanorods were synthesized by carboxyl-assisted on GO.•(101) facet Co nanorods exhibited higher surface energy of (101) facets (2.61 J/m2).•Co nanorods showed very low over-potential for proton reduction.•Co nanorods co-catalyst showed very high photocatalytic activity for H2 generation.•The apparent quantum efficiency (AQE) of Co nanorods catalyst achieved 17.4% at 520 nm.

In this paper, Co nanorods with extremely high length to diameter and preferred exposed (101) facet were synthesized by carboxyl-assisted over graphite oxide surface. DFT calculation results indicated that (101) facet Co nanorods exhibited higher surface energy of (101) facets (2.61 J/m2) than that of (100) planes nanorods (2.46 J/m2). Such Co nanorods showed very low over-potential for proton reduction, about 0.20 V onset overpotential and 400 and 510 mV at current densities of 2 and 5 mA/cm2, and worked as high active co-catalyst for photocatalytic hydrogen evolution. Co (101) nanorods loaded catalyst generated 891.3 μmol H2 in 2 h, while Co nanoparticles only gave 451.6 μmol of hydrogen during same time. The apparent quantum efficiency (AQE) of Co nanorods catalyst achieved 17.4% at 520 nm. This work opened a news strategy for design of with rodlike structure cocatalyst with preferred exposed high surface energy facet for photocatalytic hydrogen evolution reaction though the carboxylation of GO.

Graphical abstractCo nanorods showed very low over-potential for proton reduction, about 0.20 V onset overpotential and 400 and 510 mV at current densities of 2 and 5 mA/cm2, and worked as high active co-catalyst for photocatalytic hydrogen evolution.Download high-res image (139KB)Download full-size image