3. Tracking Water Splitting Activity by Cocatalyst Identity in SrTiO3

Nursaya Zhumabay, Jeremy A. Bau, Rafia Ahmad, Laurentiu Braic, Huabin Zhang, Luigi Cavallo, Magnus Rueping

Small Struct. 2025, 6, 2400283

DOI: 10.1002/sstr.202400283

Abstract:

Photocatalytic water splitting is the most idealistic route to green hydrogen production, but the extensive material requirements for this reaction make it difficult to realize good photocatalysts. Noble metal cocatalysts are often added to photocatalysts to aid in charge separation and improve surface kinetics for H2 evolution. In this study, the high activity of the promising photocatalyst Al-doped SrTiO3 is demonstrated to be ultimately dependent on the cocatalyst used as much as the presence of Al dopant. By tracking the band energetics of photocatalyst electrodes using operando electrochemical ATR-SEIRAS, cocatalysts (especially Rh) are found to shift the quasi-Fermi levels and metal-semiconductor flat-band potentials of photocatalysts in an anodic direction. Furthermore, the size of the shift directly correlates with overall water splitting activity, demonstrating that SrTiO3 becomes more active as photo-generated electrons are stabilized further from the conduction band. Rh on Al-doped SrTiO3 provides the most advantageous band tailoring as confirmed by DFT, and is experimentally found to provide this effect by eliminating Ti3+-related surface traps in the presence of Al dopants. Therefore, the effect of cocatalysts on water splitting activity is more complicated than previously thought.

Mechanochemistry RAM resonant acoustic mixing depolymerization Upcycling polymer recycling PET reuse PLA poly latic acid plastic recycling

Abstract:

This study presents a scalable mechanochemical method for the upcycling of (poly)lactic acid (PLA) into industrially valuable alkyl lactate esters via organocatalytic depolymerizing transesterification enabled by resonant acoustic mixing (RAM). The process is characterized by its simplicity, requiring neither grinding media nor a co-solvent and utilizing nearly stoichiometric amounts of an alcohol reaction partner in the presence of an inexpensive, easily accessible catalyst. Additionally, the mechanochemistry is successfully extended to the upcycling of post-consumer PLA for the synthesis of various substituted esters and lactamides.

1. Ba/Ti MOF: A Versatile Heterogeneous Photoredox Catalyst for Visible-Light Metallaphotocatalysis

I. S. Khan, L. Garzon-Tovar, R. Kancherla, N. Kolobo, A. Dikhtiarenko, M. Almalki, A. Shkurenko, V. Guillerm, K. N. Le, G. Shterk, C. H. Hendon, M. Eddaoudi, J. Gascon, M. Rueping

Adv. Mater. 2025, 37, 2405646

DOI: 10.1002/adma.202405646

Abstract:

The field of sustainable catalysis is evolving rapidly, with a strong emphasis on developing catalysts that enhance efficiency. Heterogeneous photocatalysis has emerged as a promising and mild approach to address the persistent challenges. Among various heterogeneous photocatalysts, Metal-Organic Frameworks (MOFs) have gained significant attention for their exceptional performance and recyclability in photocatalytic reactions. In this context, contrary to the conventional homogeneous Ir or Ru-based photocatalysts, which face significant challenges in terms of availability, cost, scalability, and recyclability, we have developed a new Ba/Ti MOF (ACM-4) as a heterogeneous catalyst that could mimic/outperform the conventional photocatalysts, offering a more sustainable solution for efficient chemical processes. Its redox potential and triplet energy are comparable to or higher than the conventional catalysts, organic dyes, and metal semiconductors, enabling its use in both electron transfer and energy transfer applications. It facilitates a broad range of coupling reactions involving pharmaceuticals, agrochemicals, and natural products, and is compatible with various transition metals such as Ni, Cu, Co, and Pd as co-catalysts. Notably, ACM-4 can be easily recovered and reused multiple times with minimal loss in efficiency. The effectiveness of the ACM-4 as a photocatalyst is supported by comprehensive material studies and photophysical experiments. These significant findings underscore the potential of ACM-4 as a highly versatile and cost-effective photoredox catalyst, providing a sustainable, one-material solution for efficient chemical processes.