Ni/TiO 2 Interfaces Enhance Benzaldehyde Selectivity in the Photocatalytic Dehydrogenation of Benzyl Alcohol

The selective conversion of alcohols to carbonyls (ketones and aldehydes) plays an important role in chemical manufacturing. Photocatalytic acceptorless dehydrogenation offers a light-driven alternative for producing value-added aldehydes and H 2 under mild conditions and with easy separation and high molar efficiency. However, using semiconductor photocatalysts to achieve high selectivity and long-term stability under prolonged high-intensity illumination remains challenging. In this work, we developed CdS/TiO 2 /Ni photocatalysts by depositing TiO 2 onto CdS nanoparticle panels via atomic layer deposition (ALD), followed by Ni cocatalyst photodeposition, for the acceptorless dehydrogenation of benzyl alcohol to benzaldehyde and H 2 . Diluting the benzyl alcohol concentration to a practical range of ~10 vol% (1 M) further increased benzaldehyde selectivity to ~95%. Ni photodeposition and zeta-potential measurements suggest that TiO 2 coatings progressively modify Cd 2+ -associated surface sites through Ti 3+ /Ti 4+ incorporation, altering adsorption kinetics and contributing to the reduced activity. This extends the photocatalyst’s lifespan from ~23 to 60 hours and increases cumulative benzaldehyde and H 2 production. TiO 2 thin-film coatings have emerged as a promising strategy to protect semiconductor photocatalysts while modifying surface active sites and reaction kinetics, and their stability-activity trade-off showing lower initial-stage activity beyond 15-cycle ALD will be discussed alongside proposed mechanisms. This work establishes a semiconductor/coating/cocatalyst design architecture that highlights the importance of engineering surface adsorption and active-site environments, alongside charge-separation strategies based on band-edge energetics and charge-carrier dynamics, to jointly optimize photocatalytic activity and product selectivity for targeted chemical synthesis.