Ultrathin CoOOH Oxides Nanosheets Realizing Efficient Photocatalytic Hydrogen Evolution

Producing H2 by means of direct photocatalytic water splitting using suspension system is highly desired in efficiently transforming solar energy to chemical energy. Here, using an ultrathin β-CoOOH nanosheet as photocatalyst suspended in aqueous Na2SO3 solution, we realize highly efficient and stable photocatalytic hydrogen evolution under visible light irradiation. The as-prepared ultrathin β-CoOOH nanosheets suspension can directly photocatalyze hydrogen evolution in a high rate of 1200 μmol/g/h and large quantum efficiencies of 10.7% at 380 nm, 6.9% at 420 nm, and 2.3% at 450 nm. X-ray photoelectron and X-ray absorption measurements reveal that the excellent hydrogen evolution activity of the β-CoOOH nanosheet is attributed to the surface low-coordinated Co catalytic site, which results in a strong hybridization of Co 3d states with the S p states of SO32+, and facilitates the electron transfer to reduce H+. The results may be helpful for designing and understanding two-dimensional oxyhydroxide-based photocatalyst for hydrogen production.