Cocatalyst-modified In 2 S 3 photocatalyst for C–N coupling of amines integrated with H 2 evolution

Photocatalytic hydrogen (H2) production coupled with selective oxidation of organic compounds into high-value-added organic intermediates has an expansive perspective in the utilization and transformation of solar energy, which meets the...


Contents list
Experimental procedures Fig. S1.The scanning electron microscopy (SEM) image of the blank In2S3.Table S1.ICP results for all binary composite samples.Table S2.The kinetic analysis of emission decay for In2S3 and 3%-PdS-In2S3.

Experimental procedures 1. Preparation of In 2 S 3
In2S3 was prepared by a solvothermal method.S1 In a typical procedure, 0.2932 g of InCl3•4H2O and 0.3646 g of CH5N3S were dissolved in 70 mL of mixed solution (Vethanol/Vwater = 1: 1) and stirred vigorously at room temperature for 2 h to form a homogeneous transparent solution.Then the solution was transferred to a 100 mL Teflon-lined autoclave, sealed, and maintained at 180 °C for 24 h.The product was cooled at autoclave and the resulting temperature was recovered by centrifugation and washed with deionized (DI) water and absolute ethanol several times, respectively.The final sample was fully dried overnight in a vacuum of 60 °C.

Characterization methods
X-ray photoelectron spectroscopy (XPS) measurements were performed using a Thermo Scientific ESCA Lab250 spectrometer that consists of monochromatic Al Kα as the X-ray source, a hemispherical analyzer, and a sample stage with multiaxial adjustability to obtain the composition on the surface of the samples.All of the binding energies were calibrated using the C 1s peak of the surface adventitious carbon at 284.6 eV.
The crystal phase properties of the samples were analyzed with a Bruker D8 Advance X-ray diffractometer (XRD) using Ni-filtered Cu Kα radiation at 40 kV and 40 mA in the 2 θ range from 10° to 80° with a scan rate of 0.02° per second.The elemental concentration analysis was performed using an inductively coupled plasma emission spectroscopy instrument (ICP, PerkinElmer Optima 8000).UV-vis diffuse reflectance spectroscopy (DRS) on UV-vis Spectrophotometers (Thermo Scientific Evolution 200 Series) was used to measure the optical properties of the samples with BaSO4 as the internal reflectance standard.The contact potential difference (CPD) was measured on a Kelvin probe apparatus (SKP5050, KP Technology Ltd.).The work function of the probe is calibrated to be 4.25 eV by the highly oriented pyrolytic graphite as a standard reference surface.The morphology and elemental distribution of the samples were analyzed by field-emission scanning electron microscopy (FESEM) on an FEI Nova NANO-SEM 230 spectrophotometer and transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and elemental mapping analysis using a JEOL 2100F instrument at an accelerating voltage of 200 kV.The Fourier-transformed infrared spectroscopy (FT-IR) was performed on a Thermo Scientific Nicolet iS 50 FT-IR spectrophotometer.Electron paramagnetic resonance (EPR) spectroscopic measurements were performed at room temperature using a Bruker A300 EPR spectrometer.For EPR measurements, 5 mg sample powders were dispersed in a mixed solution of 10 mL acetonitrile (CH3CN) containing 0.1 mmol benzylamine (BA) and 0.2 mmol 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), which was used as a spin-trapping agent, by ultrasonic treatment.Then, the suspension was injected into a glass capillary and the glass capillary was placed in a sealed glass tube under the argon (Ar) atmosphere.The sealed glass tube was placed in the microwave cavity of the EPR spectrometer and was irradiated with a 300 W Xe lamp (λ > 420nm) during EPR measurements at room temperature.The photoluminescence (PL) and time-resolved PL spectra for samples were analyzed on an Edinburgh Analytical Instrument F900 spectrophotometer.

Photoelectrochemical measurements
The electrochemical analysis was carried out in a three-electrode cell using a Pt plate and an Ag/AgCl electrode as the counter and reference electrode, respectively.The working electrode was prepared on fluorinedoped tin oxide (FTO) glass and the boundary of FTO glass was protected by scotch tape to make an exposed area of 0.2 cm 2 .Then, 5 mg sample was dissolved in 1 mL N,N-dimethylformamide (DMF), and 50 μL Nafion solution.The 15 μL slurry was spread onto the pretreated FTO glass.After drying at 60 °C for 1 h, the uncoated area of the electrode was isolated by epoxy resin.The photocurrent density was measured on an electrochemical workstation (Autolab M204) in 0.2 M Na2SO3 aqueous solution.The electrochemical impedance spectroscopy (EIS) was conducted in 0.5 M KCl aqueous solution containing K3[Fe(CN)6]/K4[Fe(CN)6] (0.01 M).

Cyclic Voltammetry measurement
Cyclic voltammetry was conducted on an Autolab M204 workstation in a conventional three-electrode cell.A glassy carbon working electrode was employed alongside a Pt plate counter electrode and an Ag/AgCl reference electrode.10 mM solution of the desired compounds (BA) was freshly prepared in dry acetonitrile along with 0.1 M of tetrabutylammonium hexafluorophosphate as supporting electrolyte and was examined at a scan rate of 100 mV s -1 .The solution was degassed by bubbling N2 prior to measurements.Ferrocene (E1/2 = +0.42V vs. the saturated calomel electrode (SCE) in CH3CN) was added at the end of the measurements as an internal standard to determine the precise potential scale.Potential values are given versus the normal hydrogen electrode (NHE).

Photocatalytic recycling tests
To evaluate the photocatalytic stability of the catalyst, six recycling tests were carried out and detailed experimental procedures were shown as follows.After the first run of the photocatalytic reaction, the catalysts were separated and rinsed by CH3CN three times.Afterward, the second cycle test was carried out by mixing fresh CH3CN solution containing 0.1 mmol benzylamine with the used catalyst.The subsequent recycling tests were executed analogously.

Calculation of the photoelectron lifetime (τ n ) by OCP measurement
The τn is calculated by the following formula: S2                 Note: After 2 h of visible light (λ > 420 nm) irradiation, the gaseous product was injected into DI water and detected the formation of NH4 + using a colorimetric method by Nessler's reagent (Fig. S19a, b and c).In detail, 25 mL of the reacted gas is passed into 20 mL of DI water, followed by 1 mL of potassium and sodium tartrate solution (500 mg mL −1 ), and then 1 mL of Nessler's reagent was added to the above solution.After 30 min, transfer 3 mL of the above solution to a cuvette and measure its absorbance.According to the calculation, the yield of NH3 under normal reaction conditions is in the same order of magnitude as that of Nbenzylidenebenzylamine (N-BDBA).
Table S1.ICP results for all binary composite samples.Table S2.The kinetic analysis of emission decay for In2S3 and 3%-PdS-In2S3.

Note:
The time-resolved photoluminescence (TRPL) spectrum decay curve is fitted by exponential decay kinetics function expressed as follows: S4

Fig. S5 .
Fig. S5.The gas chromatography (GC) chromatograms of the liquid reaction mixture collected at different reaction times in the presence of 3%-PdS-In2S3 composite.

Fig. S19 .
Fig. S19 .Calibration for NH4 + determination with Nessler's reagents.(a) UV-vis absorption spectra for the standard solutions of NH4 + with different concentrations.(b) Calibration curve for ammonium concentration vs. absorbance at 420 nm.(c) The UV-visible curve for NH3 measurement after reaction.
τ is the potential-dependent photoelectron lifetime, kB is Boltzmann's constant, T is the temperature, e is the charge of a single electron, and Voc is the open-circuit voltage at time t.

Fig. S5 .
Fig. S5.The gas chromatography (GC) chromatograms of the liquid reaction mixture collected at different reaction times in the presence of 3%-PdS-In2S3 composite.

Fig. S18 .
Fig. S18.The cyclic voltammetry (CV) curves of benzylamine (BA).Note:The redox potential of BA is measured to be about +0.84 V vs. Ag/AgCl, which is equivalent to +1.04 V vs. normal hydrogen electrode (NHE) according to the equation of ENHE = EAg/AgCl + 0.20 V.

Fig. S19 .
Fig. S19 .Calibration for NH4 + determination with Nessler's reagents.S3 (a) UV-vis absorption spectra for the standard solutions of NH4 + with different concentrations.(b) Calibration curve for ammonium concentration vs. absorbance at 420 nm.(c) The UV-visible curve for NH3 measurement after reaction.
The theoretical and actual contents in the table represent the content of PdS in the composite catalyst.
τ2 are the emission lifetimes.τ1 stands for the fast component, which originated from the defect state emission.τ2 stands for the slow component, which is caused by the free excitons recombination within the samples.A1 and A2 are the corresponding amplitudes.The average emission lifetime (τa), reflecting the overall emission decay behavior of samples, was also calculated through the following equation: