The enriched edge sites of SnS2 NFs substantially improve the gas sensing properties under visible light illumination.

To construct a highly efficient photoelectrochemical tandem device with silicon photocathode operating in alkaline conditions, it is desirable to develop stable and active catalysts which enable the photocathode to reliably perform under an alkaline environment. With nanostructured passivation layer and edge‐exposed transition metal disulfides, silicon photocathode provides new opportunities for achieving unbiased alkaline solar water splitting. Here, the TiO2 nanorod arrays decorated by edge‐rich MoS2 nanoplates are elaborately synthesized and deposited on p‐Si. The vertically aligned TiO2 nanorods fully stabilize the Si surface and improve anti‐reflectance. Moreover, MoS2 nanoplates with exposed edge sites provide catalytically active regions resulting in the kinetically favored hydrogen evolution under an alkaline environment. Interfacial energy band bending between p‐Si and catalyst layers facilitates the transport of photogenerated electrons under steady‐state illumination. Consequently, the MoS2 nanoplates/TiO2 nanorods/p‐Si photocathode exhibits significantly improved photoelectrochemical‐hydrogen evolution reaction (PEC‐HER) performance in alkaline media with a high photocurrent density of 10 mA cm−2 at 0 V versus RHE and high stability. By integrating rationally designed photocathode with earth‐abundant Fe60(NiCo)30Cr10 anode and perovskite/Si tandem photovoltaic cell, an unassisted alkaline solar water splitting is accomplished with a current density of 5.4 mA cm−2 corresponding to 6.6% solar‐to‐hydrogen efficiency, which is the highest among p‐Si photocathodes.

Stabilizing atomically dispersed single atoms (SAs) on silicon photoanodes for photoelectrochemical-oxygen evolution reaction is still challenging due to the scarcity of anchoring sites. Here, we elaborately demonstrate the decoration of iridium SAs on silicon photoanodes and assess the role of SAs on the separation and transfer of photogenerated charge carriers. NiO/Ni thin film, an active and highly stable catalyst, is capable of embedding the iridium SAs in its lattices by locally modifying the electronic structure. The isolated iridium SAs enable the effective photogenerated charge transport by suppressing the charge recombination and lower the thermodynamic energy barrier in the potential-determining step. The Ir SAs/NiO/Ni/ZrO2/n-Si photoanode exhibits a benchmarking photoelectrochemical performance with a high photocurrent density of 27.7 mA cm−2 at 1.23 V vs. reversible hydrogen electrode and 130 h stability. This study proposes the rational design of SAs on silicon photoelectrodes and reveals the potential of the iridium SAs to boost photogenerated charge carrier kinetics.

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