Rh-modified Cs2AgBiBr6/CdS heterojunction for synergistic photocatalytic ethanol dehydrogenation and acetalization

A ternary CABB/CdS–Rh heterojunction with Type-I band alignment and Rh electron trapping for synergistic charge separation. • DFT-Bader analysis quantifies Rh-induced charge redistribution, with net charge increased from 0.20 to 0.30 |e|. • CABB/CdS-Rh yields 49.15 mmol·g -1 ·h -1 H 2 (STH 0.19%) with tunable selectivity for acetaldehyde/acetal. Photocatalytic direct dehydrogenation of ethanol remains critically constrained by the narrow visible-light response and inefficient charge carrier separation of conventional photocatalysts. Herein, a Rh-modified Cs 2 AgBiBr 6 /CdS heterojunction is fabricated for coupled ethanol dehydrogenation, H 2 production and acetal generation under mild conditions. Density Functional Theory (DFT) calculations validate the tailored charge transfer behavior via Bader charge and differential charge density analyses. Bader charge analysis shows that Rh incorporation increases the interfacial net charge variation from 0.20 |e| to 0.30 |e| and introduces a local variation of 0.42 |e| around Rh sites, thereby suppressing charge recombination and promoting carrier separation. Control experiments confirm that 1D CdS nanorods deliver better charge transport than 2D CdS nanosheets, and surface cocatalyst anchoring is indispensable for efficient hydrogen evolution. Rh outperforms other tested metals (Pd, Pt, Au, Ni), achieving an H 2 evolution rate of 49.15 mmol·g −1 ·h −1 (20.24-fold that of CABB/CdS) and Solar-to-Hydrogen (STH) efficiency of 0.19%. Rh modification tunes liquid-phase product distribution, and the catalyst shows broad alcohol substrate adaptability and robust cycling stability. The synergistic heterojunction engineering and cocatalyst modification strategy presented in this work offers a promising catalyst design paradigm for the valorization of biomass-derived alcohols via photocatalytic conversion. A CABB/CdS-Rh heterojunction photocatalyst is constructed for visible-light-driven ethanol dehydrogenation. The reinforced interfacial charge redistribution, together with the Rh electron-trapping centers, effectively suppresses charge recombination, achieving efficient H 2 production of 49.15 mmol·g −1 ·h −1 with an STH EtOH efficiency of 0.19%. Systematic screening identifies Rh as the optimal cocatalyst, and the catalyst exhibits broad substrate adaptability toward various alcohols, including benzyl alcohol, cyclohexanol, and n-pentanol. This integrated design offers a versatile strategy for the dual valorization of biomass-derived alcohols into H 2 fuel and valuable chemicals. Download: Download high-res image (127KB) Download: Download full-size image