Wafer-scale n-MoS2/p-Si photocathodes with high hydrogen evolution reaction activities are demonstrated.

Two-dimensional transition metal disulfide (TMD) nanosheets, including MoS 2 , WS 2 , TaS 2 , and TiS 2 , were used to catalyze the hydrogen evolution reaction (HER). The TMDs were exfoliated by sonication to generate nanosheet layers that were approximately a few hundred nanometers in size. X-ray diffraction and transmission electron microscope data indicated that the major plane of the exfoliated nanosheets was the (002) plane and that the hexagonal structure is maintained after exfoliation with lattice constants of 0.32 nm for MoS 2 and WS 2 and 0.34 nm for TaS 2 and TiS 2 . Exfoliated MoS 2 , WS 2 , TaS 2 , and TiS 2 loaded on Au electrodes exhibited good electrocatalytic activity with low onset potentials of ∼100, 150, 175, and 135 mV, respectively, at a current density of −1 mA/cm 2 . MoS 2 and TiS 2 exhibited the best HER performance with Tafel slopes of 94.91 and 91 mV/decade. These results indicated that TMD nanosheets have potential applications as HER catalysts for the mass production of hydrogen.

Converting solar energy by photoelectrochemical water splitting has been regarded as a promising way to resolve the global energy crisis and alleviate environmental pollution. Silicon, which is earth-abundant and has a narrow band gap, is an attractive material for photoelectrochemical water splitting. However, Si-based photoelectrodes suffer from photocorrosion, which leads to instability in electrolytes and high overpotential. Herein, we have fabricated a metal–insulator–semiconductor structure of NiO x /Ni/n-Si photoanodes for highly efficient water splitting. NiO x /Ni nanoparticles, which act as well-known oxygen evolution catalysts, are deposited on the surface of silicon by facile pulsed electrodeposition. Light absorption and catalytic activity are greatly affected by the coverage of Ni nanoparticles, and the highly efficient NiO x /Ni catalyst structure is induced by simple annealing. The NiO x /Ni nanoparticles show highly enhanced charge separation and transport efficiency, which are vital factors for photoelectrochemical water splitting, leading to ∼100% Faradaic efficiency and incident photon-to-current efficiency. A low onset potential of 1.08 V versus a reversible hydrogen electrode for 1 mA/cm2 and a high photocurrent density of 14.7 mA/cm2 at 1.23 V are obtained.