Mo₃S₄ Clusters as an Effective H₂ Evolution Catalyst on Protected Si Photocathodes

This work shows how a molecular Mo₃S₄ cluster bonded to a photoelectrode surface via a phosphonate ligand can be a highly effective co-catalyst in photocathodic hydrogen evolution systems. Using a TiO₂ protected n⁺p Si photocathode, H₂ evolution occurs with an onset of +0.33 V vs. RHE in an acid solution with this precious metal-free system. Using just the red part of the AM1.5 solar spectrum (λ > 635 nm), a saturation current of 20 mA/cm² is achieved from an electrode containing Mo₃S₄ dropcasted onto a 100 nm TiO₂/7 nm Ti/n⁺p Si electrode.