Z‐Scheme Photocatalytic Systems for Promoting Photocatalytic Performance: Recent Progress and Future Challenges

Abstract

Semiconductor photocatalysts have attracted increased attention due to their great potential for solving energy and environmental problems. The formation of Z‐scheme photocatalytic systems that mimic natural photosynthesis is a promising strategy to improve photocatalytic activity that is superior to single component photocatalysts. The connection between photosystem I (PS I) and photosystem II (PS II) are crucial for constructing efficient Z‐scheme photocatalytic systems using two photocatalysts (PS I and PS II). The present review concisely summarizes and highlights recent state‐of‐the‐art accomplishments of Z‐scheme photocatalytic systems with diverse connection modes, including i) with shuttle redox mediators, ii) without electron mediators, and iii) with solid‐state electron mediators, which effectively increase visible‐light absorption, promote the separation and transportation of photoinduced charge carriers, and thus enhance the photocatalytic efficiency. The challenges and prospects for future development of Z‐scheme photocatalytic systems are also presented.

Solar‐to‐Hydrogen Energy Conversion Based on Water Splitting

“…On the other side, the positively charged holes will conversely transfer to the semiconductor with lower VB potential. [28][29][30] This system is akin to the aforementioned photosynthesis process in nature. The heterogeneous junction can be created by loading one semiconductor material onto another supportive semiconductor, such as C 3 N 4 sheets.…”

“…The heterogeneous junction can be created by loading one semiconductor material onto another supportive semiconductor, such as C 3 N 4 sheets. [28,30] The catalog of candidate materials for overall water splitting can be expanded with the Z-scheme strategy. For example, Li and co-workers prepared the mixture of α and β Ga 2 O 3 for overall water splitting.…”

A Review of Direct Z‐Scheme Photocatalysts

“…Specifically, the structure of a direct Z‐scheme photocatalyst is similar to that of a type‐II heterojunction photocatalyst (Figure a,b), but its charge‐carrier migration mechanism is different. Specifically, a typical direct Z‐scheme system has a charge‐carrier migration pathway that resembles the letter “Z” (Figure b) . During the photocatalytic reaction, the photogenerated electrons in semiconductor B, with lower reduction ability, recombine with the photogenerated holes in semiconductor A with a lower oxidation ability (Figure b) .…”

Evaluating particle-suspension reactor designs for Z-scheme solar water splittingviatransport and kinetic modeling

“…Our study specifically considers a tandem particle-suspension reactor for solar water splitting that relies on a two-step Z-scheme mechanism [58] and a reversible redox shuttle dissolved in an aqueous electrolyte ( Figure 1). In a Z-scheme mechanism, the thermodynamic energy requirement for water splitting (WS) is attained using two photosystems (L1 and L2), similar to natural photosynthesis.…”