Plasmonic Bi-Modified CoAl-LDH/MoO3– x S-Scheme Heterojunctions: A Comprehensive Undergraduate Laboratory Experiment for Photocatalytic CO2 Reduction to C2 Products

Abstract This work presents a comprehensive laboratory experiment tailored for advanced undergraduate students in energy, environmental science, chemistry, and materials science programs. The experiment is designed to deepen students’ understanding of hot electron dynamics, S-scheme heterojunction charge transfer, and CO2 deep photoreduction. A Bi-modified CoAl-LDH/MoO3–x S-scheme heterojunction (denoted BML) is synthesized via hydrothermal, calcination, and ultrasonic-assisted solvothermal routes, with tunable Bi loading to regulate plasmonic effects. Photocatalytic CO2 reduction tests demonstrate that the BML-2 composite exhibits optimal performance, with production rates of 23.59, 11.57, 9.58, and 5.87 μmol g–1 h–1 for CO, CH4, C2H4, and C2H6, respectively, achieving an electron selectivity of 58.5% toward C2 products. The enhanced activity is attributed to the synergistic effects of the S-scheme charge pathway, oxygen vacancy-induced light absorption, and Bi-derived localized surface plasmon resonance (LSPR) hot electrons, which promote charge separation and facilitate multielectron transfer for C–C coupling. This experiment integrates material preparation, structural characterization, performance evaluation, and mechanistic analysis into a unified teaching module, effectively cultivating students’ experimental skills, data interpretation ability, and research interest while bridging cutting-edge photocatalysis research and undergraduate laboratory education.