Ni-MOF/g-C3N4 S-Scheme Heterojunction for Efficient Photocatalytic CO2 Reduction
Muhammad Iqbal Sabir, Mahmoud Sayed, Iram Riaz, Guogen Qiu, Muhammad Tahir, Khuloud A. Alibrahim, Wang Wang
Abstract
The rapid recombination of photoinduced charge carriers in semiconductors remains a significant challenge for their practical application in photocatalysis. This study presents the design of a step-scheme (S-scheme) heterojunction composed of carbon nitride (g-C3N4) and nickel-based metal–organic framework (Ni-MOF) to achieve enhanced charge separation. The establishment of an S-scheme charge transfer configuration at the interface of the Ni-MOF/g-C3N4 heterostructure plays a pivotal role in enabling efficient charge carrier separation, and hence, high CO2 photoreduction efficiency with a CO evolution rate of 1014.6 µmol g−1 h−1 and selectivity of 95% under simulated solar illumination. CO evolution represents an approximately 3.7-fold enhancement compared to pristine Ni-MOF. Density functional theory (DFT) calculations, supported by in situ irradiated X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) experimental results, confirmed the establishment of a well-defined and strongly bonded interface, which improves the charge transfer and separation following the S-scheme mechanism. This study sheds light on MOF-based S-scheme heterojunctions as fruitful and selective alternatives for practical CO2 photoreduction.