Construction of a 3D/2D Z-Scheme Heterojunction for Promoting Charge Separation and Augmented Photocatalytic Hydrogen Evolution

Abstract

Fabrication of multidimensional heterogeneous photocatalysts combining two-dimensional (2D) and three-dimensional (3D) nanostructures is crucial for efficient solar energy conversion at the 3D/2D interface. Herein, a direct Z-scheme heterostructure has been developed by modification of the wide band gap Na0.5Bi0.5TiO3 (NBT, 3.10 eV) with graphene nanosheets via a facile hydrothermal method which demonstrated a 14-fold increase in H2 generation (∼100 mmol h–1 g–1) with an apparent quantum yield of 6.3% compared to pure NBT (∼7 mmol h–1 g–1) under visible light. The photoelectrochemical measurements reveal that the NBT/reduced graphene oxide exhibits ∼32 times enhancement in photocurrent density due to a significant increase in the charge-carrier concentration (1.8 × 1017 cm–3) of the heterostructure as compared to bare NBT (3.4 × 1016 cm–3). Remarkably, the formation of a direct Z-scheme heterojunction at the interface of graphene and NBT induces an in-built electric field and facilitates the vectorial transfer of the photogenerated charge carriers, which improves the rate of H2 generation without using noble metal-based cocatalysts. Moreover, waste-derived NBT/reduced graphene oxide from the graphite powder reclaimed from spent Li-ion batteries shows excellent photocatalysis performance comparable to natural resources. This suggests the potential for large-scale photocatalysts production from waste-derived carbon source for solar fuel generation.

Beyond the horizons of graphene: xenes for energy applications

“…The HER process is either a photo or electrochemical process by which H 2 gas is generated either using a photo or electrocatalyst, respectively. 147,148 This is mainly done over water, which results in the breakage of the H 2 O molecule to generate H 2 gas. 149,150 Recently, instead of water, other hydrogen carriers such as ammonia are also being explored for the production of hydrogen.…”

Boosting Energy Storage in Metal Batteries by Light: Progress, Challenges, and Perspectives

“…However, the fast recombination of photoexcited charge carriers in the WO 3 photoelectrode results in small photocurrent and thus poor rate capability . Establishing heterojunctions has been developed as a promising avenue to improve the separation and migration of photogenerated carriers in semiconductor photocatalysts. − The g-C 3 N 4 -decorated WO 3 nanowire array (WO 3 @g-C 3 N 4 NWA) heterojunction semiconductor photoelectrode has been rationally designed to perform as the oxygen electrode as well for the construction of a two-electrode light-responsive rechargeable Li–O 2 battery . The photocurrent density of the WO 3 @g-C 3 N 4 NWA heterostructure photoelectrode (0.27 mA cm –2 ) was higher than those of g-C 3 N 4 (0.05 mA cm –2 ) and WO 3 NWA (0.20 mA cm –2 ) due to the enhanced separation efficiency.…”