Under a Creative Commons Attribution-NonCommercial 4.0 International licence., Table S1. Comparison between the GVL yield (%) achieved in this work in comparison to the results published in literature for the same reaction in batch mode.
GC-FID calibration for continuous flow reactions:
In order to obtain the moles of the various compounds actually present at the end of the reaction, it is necessary to calibrate the instrument. Calibrations were carried out on the individual compounds, obtaining the standards by diluting the stock solution in 25mL flasks and adding 20μl of octane as an internal standard in each.
The theoretical concentrations of the stock solution and the various standards have been reported in Tables S2 and S3. The compounds used for the calibrations were: furfural (FUR), furfuryl alcohol (FAL), α-angelic lactone (AnL), propyl levulinate (PL), furfuryl ethyl ether (FEE) and γ-valerolactone (GVL). It was not possible to calibrate isopropyl levulinate (which is the molecule that is actually formed during the reaction) as it is not a commercial molecule. It was therefore decided to use its isomer (propyl levulinate) assuming that the two response factors are equal. Furfuryl isopropyl ether (FPE) is also a compound absent on the market and its response factor has been assumed to be the same as that of FEE since it was the closest molecule of those commercially available. The chromatogram obtained from the calibration of the species described is shown in Figure S1.
Table S2. List of compounds used and their quantities for the preparation of stock solutions using iPrOH as a solvent
Table S3. Concentrations of the standards prepared for each individual compound from their own stock solutions
Table S4. XPS results for the different O1s spectral region contributions, The authors would like to acknowledge the Generalitat Valenciana for CIAICO/2024/087 and CIGRIS/2022/198. The authors also thank the Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación and European Union NextGeneration EU through the projects PID2021–126235OB-C33 MCIN/AEI/10.13039/ 501100011033/FEDER Una manera de hacer Europa, UE and TED2021–129555B–I00/AEI/10.13039/501100011033/Unión Europea NextGenerationEU/PRTR., Peer reviewed

This study reports the bio-mediated synthesis of tungsten trioxide nanostructures from aqueous extracts of Melia
azedarach (L.) dry leaves. The synthesis was carried out by electrochemical anodization of tungsten foils in the
presence of different volume percentages of leaves extracts. These nanostructures were afterwards
characterized by X-Ray Diffraction (XRD), impedance measurements and linear sweep voltammetry
in the presence of simulated solar light. Finally, these nanoelectrodes were used as
(photo)electrocatalysts in the photoelectrochemical water splitting process to obtain green hydrogen and as
anodes in Li-ion rechargeable batteries.

Description of methods used for collection/generation of data:

- Synthesis of WO3 nanostructures:

The leaves of M. azedarach were randomly sampled from several
mature trees from the surroundings of the Burjassot Campus of the
University of Valencia (Spain). Fresh leaves were rinsed with tap and
distilled water and subsequently air-dried indoors for 1 week, at room
temperature. The extracts were obtained from dried leaves, by mixing
15 g of material with 150 mL of distilled water at 60 ºC. The infusion was
maintained at that temperature for 20 min. After that, the solution, once
cooled, was filtered through filter paper and used to prepare the
different reaction media.
Nanostructures of WO3 were synthesized by subjecting tungsten foils
(1,3 cm2 of exposed area) to an anodization process with a cell potential
of 20 V, for 4 h. A platinum foil served as the cathode within the cell. The
anodization process employed an aqueous electrolyte composed of
1.5 M methanesulfonic acid (MSA) with varying proportions of M.
azedarach leaves extract (from 0% to 10%, in volume), at a temperature
of 50◦C. Anodization was performed under
controlled hydrodynamic conditions, by means of a Rotating Disk
Electrode (RDE) set a constant rotation speed of 750 rpm. Following
anodization, a thermal treatment (annealing) was carried out in a
tubular oven at 600◦C for 4 h in an air atmosphere to obtain crystalline
WO3 nanostructures.


- Morphological and structural characterization:

X-Ray diffraction analyses (XRD) were performed to investigate the
crystallinity of the WO3 samples. A D8AVANCE diffractometer (Bruker)
equipped with a monochromatic Cu Kα1 source was used.


-(Photo)electrochemical characterization: impedance measurements
and photocurrent density vs potential curves:

Electrochemical characterization of the WO3 nanostructures was
conducted through impedance measurements, performing Electrochemical
Impedance Spectroscopy (EIS) and Mott-Schottky (MS) analyses.
All electrochemical tests were carried out using a three-electrode
cell with the nanostructures acting as working electrodes, a silver/silver
chloride (3 M KCl) electrode was the reference electrode and a platinum
tip served as counterelectrode. Measurements were performed with a
PalmSens4 potentiostat and 0.1 M H2SO4 was used as electrolyte. The
sample area exposed to that electrolyte was 0.5 cm2. For EIS, a constant
potential of 1 V was selected with an amplitude of 10 mV, scanning the
frequency from 100 kHz to 10 mHz. For MS analysis, a constant frequency
of 5 kHz was used, while the potential was scanned from 1 V to
0.2 V at a rate of 50 mV/s.
For the photoelectrochemical characterization of the WO3 nanostructures,
the same experimental set-up was used, with the addition of a
solar simulator with AM 1.5 conditions (100 mW/cm2). Linear voltammetries
to obtain photocurrent density – potential curves were
conducted from 0.2 V to 1.05 V, by applying dark-light pulses (16 s in
the dark followed by 4 s with illumination) while the potential was
scanned.

- Evaluation of WO3 nanostructures as Li-ion battery anodes:

WO3 nanostructures were evaluated as anodes (negative electrodes)
for Li-ion batteries. For that purpose, Swagelok-type cells were used,
with WO3 nanostructures acting as working electrodes and a metallic
lithium foil acting as both the counter and the reference electrodes.
Batteries were assembled inside an Ar-filled glove box, using 1 M LiPF6
in ethylene carbonate/dimethyl carbonate/diethyl carbonate 1:1:1 (v/
v/v) as electrolyte (Sigma-Aldrich) and a Whatman glass microfiber
separator. After sealing the cells, they were cycled outside the glove box
at room temperature, using a Biologic BCS-815 cyclic station. Galvanostatic
charge/discharge curves were recorded at different cycling
rates (from C/10–1 C, and returning to C/10) within a potential window
between 1 V and 3.5 V vs Li/Li+.

CuOx (x = 1 and 2) nanostructures have been synthesized by electrochemical anodization in ethylene glycol based electrolytes using oxalic acid or NaF (with or without NaOH) as complexing agents. The influence of hydrodynamic conditions and time during anodization of copper have also been evaluated. An electrochemical and photoelectrochemical characterization of the nanostructures has been performed.

An electrochemical and photoelectrochemical characterization of WO3 nanostructures has been performed by means of Electrochemical Impedance Spectroscopy and Mott–Schottky measurements, as well as using cyclic voltammetry and Photocurrent density curves.