Systematic Constructing FeOCl/BiVO4 Hetero-Interfacial Hybrid Photoanodes for Efficient Photoelectrochemical Water Splitting

Visible-light-driven selective cleavage of lignin C-C bonds on the TiO2@g-C3N4heterostructured photocatalyst

The selective cleavage of lignin C-C bonds is a highly sought-after process with the goal of obtaining low-molecular-weight aromatic chemicals from renewable resources. However, it remains a challenging task to achieve under mild conditions. Photocatalysis is a potentially promising approach to address this issue, but the development of efficient photocatalysts is still in progress. In this study, we introduce the heterostructured TiO2@g-C3N4photocatalyst for the development of a visible light photocatalytic procedure for the selective cleavage of lignin C-C bonds under mild conditions. The photocatalyst displays favourable visible light absorption, efficient charge separation efficiency, and promising reusability. A typicalβ-O-4 dimer model, 2-phenoxy-1-phenylethanol, was effectively (96.0% conversion) and selectively (95.0 selectivity) cleaved under visible light at ambient conditions. This photocatalytic procedure was also effective when subjected to solar irradiation or other lignin dimer models withβ-O-4 orβ-1 linkages. This reaction occurred through a Cβ-centred radical intermediate and a six-membered transition state with photogenerated holes as the primary active species. The Cα-OH oxidative dehydrogenation of the substrate could also take place but was a relatively minor route. This study provides a new photocatalytic procedure for visible-light-driven lignin valorisation and sheds light on the design of high-performance nanocomposite photocatalysts for C-C bond cleavage.

Tethering Cobalt Ions to BiVO4 Surface via Robust Organic Bifunctional Linker for Efficient Photoelectrochemical Water Splitting

In the quest for efficient and stable oxygen evolution catalysts (OECs) for photoelectrochemical water splitting, the surface modification of BiVO4 is a crucial step. In this study, a novel and robust OEC, based on 3-(bis(pyridin-2-ylmethyl) amino) propanoic acid bifunctional linker known as dipicolyl alanine acid (DPAA) and cobalt ions, is prepared and fully characterized. The DPAA is anchored to the surface of BiVO4 and utilized to tether cobalt ions. The Co-DPAA/BiVO4 photoanode exhibits remarkable stability and efficiency toward photoelectrochemical water oxidation. Specifically, it showed anodic photocurrent increase of 7.1, 5.0, 3.0, and 1.3-fold at 1.23 VRHE as compared to pristine BiVO4, DPAA/BiVO4, Co-BiVO4, and Co-Pi/BiVO4 photoanodes, respectively. The photoelectrochemical and IMPS studies revealed that the Co-DPAA/BiVO4 photoanode exhibits a longer transient decay time for surface-trapped holes, higher charge transfer kinetics, and charge separation efficiency compared to Co-Pi/BiVO4 and pristine BiVO4 photoelectrodes. This indicates that the Co-DPAA effectively reduces surface recombination and facilitates charge transfer. Moreover, at 1.23 VRHE, the Co-DPAA/BiVO4 photoanode achieved a faradic efficiency of 92% for oxygen evolution reaction and could retain a turnover frequency of 3.65 s-1. The- exhibited effeciency is  higher than most of the efficient molecular oxygen evolution catalyst based on Ru.

Strain-Induced Photocatalytic H2 Production over BiVO4 in Pure Water without Any Cocatalyst

In this study, BiVO4 nanosheets (BiVO4-NS) were prepared by a facile hydrothermal method. It is found that sonication-induced strain can effectively promote the H2 production over BiVO4-NS in the presence of pure water without any cocatalysts. With the assistance of the sonication, the H2 production over BiVO4-NS is 1.344 mmol·g-1 after 3 h simulated sunlight irradiation, which is 24.8 times higher than that of BiVO4-NS without sonication (0.054 mmol·g-1). In addition, the products of water oxidation are determined to be hydroxyl radicals and hydrogen peroxide. Moreover, BiVO4-NS also shows obviously enhanced photoactivity than that of the commercially available BiVO4 nanoparticles (BiVO4-C). The improved photoactivity of BiVO4-NS is attributed to the effective charge separation and low charge transfer resistance. The underlying mechanism of sonication-promoted water splitting is investigated by a variety of controlled experiments. The results show that ultrasonic waves can produce obvious strain inside the sample, which results in lattice distortion of BiVO4. Therefore, the conduction band of BiVO4 is obviously negative shifted, which is beneficial for H2 production. In addition, the strain in BiVO4 also produces local polarization of the sample, which effectively promotes the charge transfer and separation process. It is hoped that our study could provide a new strategy for achieving efficient photocatalytic water splitting.

Advancing BiVO4 Photoanode Activity for Ethylene Glycol Oxidation via Strategic pH Control

The photoelectrochemical (PEC) conversion of organic small molecules offers a dual benefit of synthesizing value-added chemicals and concurrently producing hydrogen (H2). Ethylene glycol, with its dual hydroxyl groups, stands out as a versatile organic substrate capable of yielding various C1 and C2 chemicals. In this study, we demonstrate that pH modulation markedly enhances the photocurrent of BiVO4 photoanodes, thus facilitating the efficient oxidation of ethylene glycol while simultaneously generating H2. Our findings reveal that in a pH = 1 ethylene glycol solution, the photocurrent density at 1.23 V vs. RHE can attain an impressive 7.1 mA cm-2, significantly surpassing the outputs in neutral and highly alkaline environments. The increase in photocurrent is attributed to the augmented adsorption of ethylene glycol on BiVO4 under acidic conditions, which in turn elevates the activity of the oxidation reaction, culminating in the maximal production of formic acid. This investigation sheds light on the pivotal role of electrolyte pH in the PEC oxidation process and underscores the potential of the PEC strategy for biomass valorization into value-added products alongside H2 fuel generation.