Metal Vacancies in CoAl-Layered Double Hydroxide Nanosheets Enabling Boosted Visible Light Driven CO2 Photoreduction

Despite the fact that defect engineering is a promising strategy to enhance the CO2 photoreduction activity of layered double hydroxides (LDHs), information to construct a suitable model for revealing the role of metal vacancies in adjusting activity is still insufficient. Herein, by modifying CoAl-layered double hydroxide nanosheets (denoted as CoAl-LDH) with NaOH etching (denoted as CoAl-LDH-NaOH) to selectively remove aluminum (Al), we construct clear models of CoAl-LDH and CoAl-LDH-NaOH with Al vacancies. Inductively coupled plasma emission, electron spin resonance, and positron annihilation spectrometry verify the introduction of Al vacancies in CoAl-LDH-NaOH. Density functional theory calculations and experiments clarify that the existence of Al vacancies modulates the electron states and thus induces better light absorption and carrier transfer. Besides, the Al vacancies can provide optimized atomically active sites for both H2O and CO2 adsorption. In consequence, CoAl-LDH-NaOH with Al vacancies show a H2 evolution rate of 277.9 mu mol g-1 h-1 and a CO evolution rate of 1349.2 mu mol g-1 h-1, roughly 3.9 and 2.4 times higher than those of CoAl-LDH. This work discloses the influences of metal vacancies on CO2 photoreduction process and presents a promising way for achieving highly efficient photoreduction of CO2.