Design Guidelines of Insulator for Improving Stability and Performance of Nanoelectrocatalyst/Insulator/Semiconductor Photoelectrochemical Cells

Abstract

Electrocatalyst/insulator/semiconductor configurations have been considered as promising designs for efficient photoelectrochemical (PEC) water-splitting reactions. However, the roles and effects of the insulator on the PEC reactions have not been clearly understood, in particular, for the nanoelectrocatalyst integrated semiconductor. In this study, we investigated the effects and ability of insulator material and thickness in terms of the stability and performance for PEC alkaline water reduction reaction by integrating nanocrystalline NiO x electrocatalyst/insulator/p-Si photocathodes. This was clearly understood by comparing the stability and performance of amorphous TiO x and SiO2. We demonstrated that the a-TiO x with low barrier height for electron transfer relative to that for hole transfer shows the ability for selective collection of photogenerated minority charge (electron) carriers. This enables a high open circuit potential while minimizing the kinetic overpotential required for electron transfer. The a-TiO x also renders excellent passivation ability for the Si surface defects, minimizing the recombination loss. In addition to these PEC performance improvements, the ability to protect completely the Si surface against corrosive electrolyte permeating through the nanocrystalline NiO x ensures long-term stability. All these abilities were maximized by optimizing the thickness of the a-TiO x (10 nm), thereby enabling the sustainable generation of a photocurrent of 10 mA/cm2 at a high potential level of 0.3 V (vs reversible hydrogen electrode). These results present design guidelines for the insulator along with methods to determine the effects of the insulator on PEC responses.

Gradient‐Structuring Manipulation in Ni3S2 Layer Boosts Solar Hydrogen Production of Si Photocathode in Alkaline Media

“…[23,47] Such a thin SiO x layer not only allows the facile tunneling of electrons but also reduces interface recombination by providing a barrier to reflect holes back into the bulk, which will benefit the device performance. [47][48][49][50] The crystalline structure of the asprepared samples was characterized by X-ray diffraction (XRD) (Figure S6, Supporting Information). All diffraction peaks of G-Ni 3 S x O 2−x /p-Si can be indexed to the crystalline planes of Ni 3 S 2 (JCPDS no.…”

Strategies for improving photoelectrochemical water splitting performance of Si‐based electrodes

“…77,115,116,120,121 Lee and Park et al prepared a nanocrystalline TiO x film protected p-Si via ALD technology, which ran stably for 40 hours in 1.0 M of KOH solution. 122 Moreover, a dense Ni film is also a good protection lay in alkaline solution. 105 In fact, the Si/ semiconductor layers (Section 3.2.2.1) and metal/insulator layers discussed in MIS structure (Section 3.2.2.3) can also be used as a protection layer, 83 as well as cocatalyst layers (see below).…”

“…In an alkaline solution, a TiO 2 layer can also effectively protect Si from corrosion 77,115,116,120,121 . Lee and Park et al prepared a nanocrystalline TiO x film protected p‐Si via ALD technology, which ran stably for 40 hours in 1.0 M of KOH solution 122 105 .…”

“…131 Thus, n-Si/SiO 2 /RuO 2 photoanodes could perform high OER performance. [132][133][134] In addition, non-noble metal and oxide/hydroxide have made outstanding contributions to reduce the overpotential of water oxidation and enhance the | 13 CHENG et al durability of Si-based photoanodes, including the bifunctional Ni-Mo, 90 Ni-Fe, 84,85,117 Fe 3 O 4 , 32 NiO x , 88,122 Co 3 O 4 , 135 NiMoO 4 , 136 and NiOOH. 71,84 And during the OER process, the surface metals are prone to be oxidized and then converted into higher active oxides/hydroxides.…”

Photo/Bio‐Electrochemical Systems for Environmental Remediation and Energy Harvesting

“…Tremendous works have been reported on PEC-based systems for solar energy harvesting and environmental remediation, respectively. However, many of them focused on the selection and design rules of the electrode materials, [21][22][23][24] strategies for improving electrode's activity [48,49] , stability, [50,51] and fundamental physics and chemistry of PECs. [52,53] A systematic summary and comprehensive discussion on the recent development of photo/bio-electrochemical system is still missing.…”