Organic TCNQ cocatalysts-modified AgGaS2 with surface configuration-dependent performance enhancement in H2O2 photosynthesis

Modifying the surfaces of photocatalysts with organic cocatalysts is effective in promoting the photosynthesis of hydrogen peroxide (H 2 O 2 ), a versatile oxidant and environmentally benign fuel. Although the configuration of organic molecules dictates their properties and performance, it has not been discussed in organic-cocatalyst-modified photocatalysts. Herein, in order to study this potential influence on H 2 O 2 photosynthesis, we have managed to prepare tetracyanoquinodimethane (TCNQ)-modified silver thiogallate (AgGaS 2 ) nanoclusters with two different surface configurations via an active photodeposition strategy pioneered in this work (T/A-light) and a conventional stirring-adsorption process in the dark (T/A-dark). It has been confirmed that TCNQ adopts an end-on configuration and serves as a surface-coordinated molecular cocatalyst with a surface charge-transfer doping effect in T/A-light, whereas it takes a face-to-face geometry and establishes a heterojunction in T/A-dark. Moreover, T/A-light displays better light absorbance, oxygen adsorption and activation, H 2 O 2 selectivity, and photocatalytic activity with small amount of TCNQ (ω(TCNQ)); while its performance is overtaken by T/A-dark as ω(TCNQ) increases via multilayer adsorption which further strengthens interfacial electric fields and facilitates the charge separation and H 2 O 2 desorption. The highest production rate reaches 2.11 mmol g −1  h −1 , which is nearly four times that of pristine AgGaS 2 and better than that of most counterparts. This work has shed light on the configuration-dependent performance of organic cocatalysts and concurrently expanded the concept and application of photodeposition, offering a significant insight into designing high-performance surface-modified photocatalysts.