Semiconductor/Faradaic layer/liquid junctions have been widely used in solar energy conversion and storage devices. However, the charge transfer mechanism of these junctions is still unclear, which leads to inconsistent results and low performance of these devices in previous studies. Herein, by using Fe 2 O 3 and Ni(OH) 2 as models, we precisely control the interface structure between the semiconductor and the Faradaic layer and investigate the charge transfer mechanism in the semiconductor/ Faradaic layer/liquid junction. The results suggest that the short circuit severely restricts the performance of the junction for both solar water splitting cells and solar charging supercapacitors. More importantly, we also find that the charge-discharge potential window of a Faradaic material sensitively depends on the energy band positions of a semiconductor, which provides a new way to adjust the potential window of a Faradaic material. These new insights offer guidance to design high-performance devices for solar energy conversion and storage.

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Two-electrode solar rechargeable devices trigger intense attention due to their potential applications in solar energy conversion and storage.H owever,i nterface energy barriers lead to severe loss of output voltage and negligible dark discharge current. Therefore,external biases are required for dark discharge in these devices,l imiting their practical applications.H erein, we report an ew two-electrode device of Si/WO 3 /H 2 SO 4(aq) /C that can work without bias.The device has the highest dark output power among all of the two-electrode solar rechargeable devices.T he device based on aS i/WO 3 junction indicates photoinduced adjustable interface barrier height during charge transfer,w hich can overcome the energy barrier and realized ark dischargew ithout bias.O wing to the interface characteristics,t he Si/WO 3 is designated as ac apacitor-type Faradaic junction.

The intrinsic faradaic layer in an oxide photoelectrode can accelerate interface charge collection and oxygen evolution reaction kinetics simultaneously.

It has been extensively focused on the development of photoelectrochemical (PEC) solar water splitting cells due to the urgent need for clean energy. In this study, InGaN/GaN multiple quantum wells (MQWs) nanorods (NRs) PEs are purposely designed with coupled plasmonic metal (Ag-Au core-shell nanowires) for high efficiency PEC water splitting, aiming for enhancing visible light absorption and carrier kinetic energy. By means of self-organized Nickel island patterning and ICP dry etching with proper depths, the photocurrent density of InGaN/ GaN nano-photoanodes in NaCl solution can be significantly enhanced from 0.74 mA cm −2 to 1.4 mA cm −2 at 1.5 V versus RHE (reversible hydrogen electrode). Furthermore, by decorating plasmonic metal into the InGaN/GaN NR arrays, the PEC water splitting performance can reach a maximum photocurrent of 1.77 mA cm −2 at 1.5 versus RHE. Such improvement is mainly attributed to the synergistic effects of the visible light absorption of MQWs and the generation of surface plasmon resonance (SPR). The approach of plasmon-enhanced nanostructure with the III-nitride based nano-PEs will accelerate the developments of visible light photocatalysts for PEC solar cells.

Two-electrode solar rechargeable devices trigger intense attention due to their potential applications in solar energy conversion and storage.H owever,i nterface energy barriers lead to severe loss of output voltage and negligible dark discharge current. Therefore,external biases are required for dark discharge in these devices,l imiting their practical applications.H erein, we report an ew two-electrode device of Si/WO 3 /H 2 SO 4(aq) /C that can work without bias.The device has the highest dark output power among all of the two-electrode solar rechargeable devices.T he device based on aS i/WO 3 junction indicates photoinduced adjustable interface barrier height during charge transfer,w hich can overcome the energy barrier and realized ark dischargew ithout bias.O wing to the interface characteristics,t he Si/WO 3 is designated as ac apacitor-type Faradaic junction.

The TiO 2 /SnO 2 composite nanocrystal with different mol ratios was prepared using the sol-gel technology and the effect of SnO 2 addition on the phase transformation of TiO 2 photocatalyst was discussed in the study as the crystal phase affects the photocatalysis greatly. The phase transformation process of pure TiO 2 and SnO 2 /TiO 2 composite powders were characterized by using X-ray diffraction, differential scanning calorimetry and thermo-gravimetry analysis. A small quantity of SnO 2 in the form of chloride accelerates the anatase-to-rutile transformation greatly. The substitution of larger-size tetravalent tin ion Sn 4+ for titanium ion Ti 4+ induces the lattice dilatation of titania crystal while the rutile-structured cassiterite plays as nucleating agent and facilitates the formation of rutile phase.

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