Cooperative Motion in Water-Methanol Clusters Controls the Reaction Rates of Heterogeneous Photocatalytic Reactions

Unveiling the Role of Water in Heterogeneous Photocatalysis of Methanol Conversion for Efficient Hydrogen Production

Water molecules, which act as both solvent and reactant, play critical roles in photocatalytic reactions for methanol conversion. However, the influence of water on the adsorption of methanol and desorption of liquid products, which are two essential steps that control the performance in photocatalysis, has been well under-explored. Herein, we reveal the role of water in heterogeneous photocatalytic processes of methanol conversion on the platinized carbon nitride (Pt/C3N4) model photocatalyst. In situ spectroscopy techniques, isotope effects, and computational calculations demonstrate that water shows adverse effects on the adsorption of methanol molecules and desorption processes of methanol oxidation products on the surface of Pt/C3N4, significantly altering the reaction pathways in photocatalytic methanol conversion process. Guided by these discoveries, a photothermal-assisted photocatalytic system is designed to achieve a high solar-to-hydrogen (STH) conversion efficiency of 2.3 %, which is among the highest values reported. This work highlights the important roles of solvents in controlling the adsorption/desorption behaviours of liquid-phase heterogeneous catalysis.

Carbon nitride nanosheet-supported CuO for efficient photocatalytic CO2 reduction with 100% CO selectivity

The optimal ratio of reaction solutions resulted in excellent performance and product selectivity of CuO/g-C3N4 composites in the photocatalytic CO2 reduction reaction. A pH-dependent chemical exchange saturation transfer (CEST) imaging nuclear magnetic resonance (NMR) method was used to confirm that CuO modification improves the adsorption capacity of CO2.

Atomic Ruthenium-Promoted Cadmium Sulfide for Photocatalytic Production of Amino Acids from Biomass Derivatives

Amino acids are the building blocks of proteins and are widely used as important ingredients for other nitrogen-containing molecules. Here, we report the sustainable production of amino acids from biomass-derived hydroxy acids with high activity under visible-light irradiation and mild conditions, using atomic ruthenium-promoted cadmium sulfide (Ru1/CdS). On a metal basis, the optimized Ru1/CdS exhibits a maximal alanine formation rate of 26.0 molAla ⋅ gRu -1 ⋅ h-1, which is 1.7 times and more than two orders of magnitude higher than that of its nanoparticle counterpart and the conventional thermocatalytic process, respectively. Integrated spectroscopic analysis and density functional theory calculations attribute the high performance of Ru1/CdS to the facilitated charge separation and O-H bond dissociation of the α-hydroxy group, here of lactic acid. The operando nuclear magnetic resonance further infers a unique "double activation" mechanism of both the CH-OH and CH3-CH-OH structures in lactic acid, which significantly accelerates its photocatalytic amination toward alanine.

Salinity-mediated water self-purification via bond network distorting of H2O molecules on DRC-surface

High salinity has plagued wastewater treatment for a long time by hindering pollutant removal, thereby becoming a global challenge for water pollution control that is difficult to overcome even with massive energy consumption. Herein, we propose a novel process for rapid salinity-mediated water self-purification in a dual-reaction-centers (DRC) system with cation-π structures. In this process, local hydrogen bond networks of H2O molecules can be distorted through the mediation of salinity, thereby opening the channels for the preferential contact of pollutants on the DRC interface. As the result, the elimination rate of pollutants increased approximately 32-fold at high salinity (100 mM) without any external energy consumption. Our findings provide a novel technology for high-efficiency and low-consumption water self-purification, which is of great significance in environmental remediation and even fine chemical industry.

Rapid detection of donor-dependent photocatalytic hydrogen evolution by NMR spectroscopy

Understanding molecular processes at nanoparticle surfaces is essential for designing active photocatalytic materials. Here, we utilize nuclear magnetic resonance (NMR) spectroscopy to track photocatalytic hydrogen evolution using donor molecules and water isotopologues. Pt-TiO₂ catalysts were prepared and used for isotopic hydrogen evolution reactions using alcohols as electron donors. ¹H NMR monitoring revealed that evolution of the H₂ and HD species is accompanied by the oxidation of donor molecules. The isotopic selectivity in the hydrogen evolution reaction gives rise to formal overpotential. Based on a comparison of the rates of hydrogen evolution and donor oxidation, we propose the use of ethanol as an efficient electron donor for the hydrogen evolution reaction without re-oxidation of radical intermediates.

Dynamics of Heterogeneous Catalytic Processes at Operando Conditions

The rational design of high-performance catalysts is hindered by the lack of knowledge of the structures of active sites and the reaction pathways under reaction conditions, which can be ideally addressed by an in situ/operando characterization. Besides the experimental insights, a theoretical investigation that simulates reaction conditions-so-called operando modeling-is necessary for a plausible understanding of a working catalyst system at the atomic scale. However, there is still a huge gap between the current widely used computational model and the concept of operando modeling, which should be achieved through multiscale computational modeling. This Perspective describes various modeling approaches and machine learning techniques that step toward operando modeling, followed by selected experimental examples that present an operando understanding in the thermo- and electrocatalytic processes. At last, the remaining challenges in this area are outlined.