Effects of RhCrO_x Cocatalyst Loaded on Different Metal Doped LaFeO₃ Perovskites with Photocatalytic Hydrogen Performance under Visible Light Irradiation

Round 1

Reviewer 1 Report

The authors report the preparation of Pr-doped LaFeO₃ and investigated to influence of several synthetic and operating parameters on H₂ photoproduction using RhCrO_x as co-catalyst. Some of the results presented may be of interest but the manuscript must be improved before acceptance.

• along the whole manuscript, results should be better discussed in the context of literature.
• Many reports describe the use of pure LaFeO₃ or of LaFeO₃-based heterostructured photocatalysts for H₂ production (the following references should be added: Int. J Hydrogen Energy 2016, 41, 959-966; Int. J. Hydrogen Energy 2020, 45, 17408-17479).
• introduction : the authors must highlight the novelty of their work and the advances made.
• Figure 6 and the related text: the actual content in Pr of LaFeO₃ should be determined, for example via ICP analysis.
• the authors must compare the efficiency of Pr-doped LaFeO₃ catalysts for H₂ photoproduction to other LaFeO₃-based catalysts described in the literature and highlight the advances made.
• the quality of the figures can be improved.

Author Response

Response to Reviewer 1 Comments

1. along the whole manuscript, results should be better discussed in the context of literature

Reply:

Thank you for your comments. More discussion adds in the context. Please follow red color words.

 

2. Many reports describe the use of pure LaFeO₃ or of LaFeO₃-based heterostructured photocatalysts for H₂ production (the following references should be added: Int. J Hydrogen Energy 2016, 41, 959-966; Int. J. Hydrogen Energy 2020, 45, 17408-17479)

Reply:

Please let me give some comments on these two papers. For Int. J Hydrogen Energy 2016, 41, 959-966, Production of hydrogen from glucose by LaFeO₃ based photocatalytic process during water treatment, prepared pure LaFeO₃ and produced of H₂ in glucose. For Int. J. Hydrogen Energy 2020, 45, 17408-1747, Heterostructured thin LaFeO₃/g-C₃N₄ films for efficient photoelectrochemical hydrogen evolution, it is prepared LaFeO₃/g-C₃N₄ films for efficient photoelectrochemical hydrogen evolution.

Our study is different from these two papers and other publishers. We focused on metal-doped LaFeO₃ and RhCrO_x as the cocatalyst in the TEOA solution, improve that H₂ activity.

 

3. introduction : the authors must highlight the novelty of their work and the advances made

Reply:

We have highlighted the novelty in the introduciton.

 

4. Figure 6 and the related text: the actual content in Pr of LaFeO₃ should be determined, for example via ICP analysis.

Reply:

The Pr mass doping LaFeO3 by ICP data shown in the 126 and 127 lines of section 2.2

 

5. the authors must compare the efficiency of Pr-doped LaFeO₃ catalysts for H₂ photoproduction to other LaFeO₃-based catalysts described in the literature and highlight the advances made.

Reply:

We summarized other LaFeO₃ based catalysts and compare the efficiency rate of H₂ evolution for Pr-doped LaFeO₃ in the following Table. However, we are difficult to compare their rate of production H₂ because they used different sacrificial agents, co-catalyst, light source, and the distance between light source and photocatalysts. Besides AQY, most papers compared the rate of H₂ evolution for without doped and metal-doped.

 

Photocatalysts	Sacrificial agents	Co-catalyst	Light source	Rate of H2 evolution	Reference
Pr-doped LaFeO3	20%TEOA solution	RhCrOx	350 W Xe lamp	94.8 mmol h−1 g−1	This work
Rh-Doped LaFeO3	Glucose		UV-LEDs 10W, light intensity:57 mW/cm2) 375–380 nm	3822 μmol h-1g-1L-1	[1]
Ru-doped LaFeO3	Glucose	-	UV-LEDs 10W, light intensity:57 mW/cm2) 375–380 nm	875μmol h-1g-1	[2]
LaFeO3	Glucose	-	UV-LEDs 10W, light intensity:57 mW/cm2) 375–380 nm	400μmol h-1g-1	[3]
Ru-LaFeO3/Fe2O3	Glucose		visible LEDs, 440 nm	1000 h-1g-1L-1	[4]
Nano LaFeO3	Ethanol solution	19μlPt	400 W tungsten light sources	3315μmol h-1g-1	[5]
Polyaniline-coverd LaFeO3	10%TEOA	3%Pt	300 W Xe lamp	92.4 μmol h-1	[6]
Ternary LaFe0.8 / LaCu0.2 catalysts	12.5% HCHO solution		UV light (cut-off λ < 400 nm) 125W Xe lamp	250 μmol h-1g-1	[7]

 

[1] Vaiano,V.; Iervolino,G.; Sannino, D. Enhanced photocatalytic hydrogen production from glucose on Rh-doped LaFeO₃, Chem. Eng. Trans., 2017, 60, 235-240.

[2] Iervolino, G.; Vaiano,V.; Sannino, D; Rizzo, L.; Palma, V. Enhanced photocatalytic hydrogen production from glucose aqueousmatrices on Ru-doped LaFeO₃, Appl. Catal. B-Enviro. 2017, 207, 182–194.

[3] Iervolino, G.; Vaiano, V.; Sannino, D.; Rizzo, L.; Ciambelli, P. Production of hydrogen from glucose by LaFeO₃ based photocatalytic process during water treatment, Int. J. Hydrog. Energy, 41, 2016, 959-966

[4] Iervolino, G.; Vaiano, V.; Sannino, D.; Rizzo, L.; Galluzzi, A.; Polichetti, M.; Pepe, G.; Campiglia, P. Hydrogen production from glucose degradation in water and wastewater treated by Ru-LaFeO₃/Fe₂O₃ magnetic particles photocatalysis and heterogeneous photo-fenton, Int. J. Hydrog. Energy, 43, 2018, 2184-2196.

[5] Tijare, S.N.; Joshi, M.V.; Padole, P.S.; Mangrulkar, P.A.; Rayalu, S.S.; Labhsetwar, N.K. Photocatalytic hydrogen generation through water splitting on nano-crystalline LaFeO₃ perovskite, Int. J. Hydrog. Energy, 13, 2012, 10451-10456.

[6] Chen, Z.; Fan, T.; Zhang, Q.; He, J.; Fan, H.; Sun, Y.; Yi, X.; Li, J. Interface engineering: Surface hydrophilic regulation of LaFeO₃ towards enhanced visible light photocatalytic hydrogen evolution, J. Colloid Interface Sci. 2019, 536, 105-111.

[7] Li, J.; Pan, X.; Xu, Y.; Jia, L.; Yi, X.; Fang, W. Synergetic effect of copper species as cocatalyst on LaFeO₃ for enhanced visible-light photocatalytic hydrogen evolution, Int. J. Hydrog. Energy, 2015, 40, 13918-13925.

 

6. The quality of the figures can be imporved.

Replay:

The quality of all Figures has been improved. We tried our best to make the highest quality of all Figures. However, the word 2016 has maximized the limit 330 ppi quality for Figures.

Reviewer 2 Report

Investigation described in manuscript catalysts-1195459 is concerning were important issue of properties of perovskites doped with different elements for application in hydrogen generation processes. These group of materials posses interesting and promising properties for application in H₂ generation processes using solar energy, therefore it may become an important "green" technology.

The manuscript describes interesting and valuable results. However, there are some minor remarks which need to be answered:

1) Is XRD sufficient to determine real chemical composition of obtained perovskites as XRD patterns for each material is quite similar (Figure 3) Chemical analysis of the material could present the real composition of investigated materials.

2) All abbreviations present in the text should be explained, e.g., PL, DSR etc.

3) Figure 6 - trend line should be presented only for positive values of Pr concentrations as it has no physical sense for negative ones.

4) Figure 11 - meaning of violet and blue lines should be explained

5) line 79 - "effects ... was"

Author Response

1. Is XRD sufficient to determine real chemical composition of obtained perovskites as XRD patterns for each material is quite similar (Figure 3) Chemical analysis of the material could present the real composition of investigated materials.

Reply:

A small amount of different metal-doped LaFeO3 usually get similar XRD patterns, and the results also confirm by other publishers.For example, Ca doped LaFeO₃ (J. Nanosci. Nanotechnol. 2011, 11, 1429–1433), Mg doped LaFeO₃ and Zn doped LaFeO₃ (ChemSusChem, 2017, 10, 2457-2463) , P doped LaFeO₃ (Nano Energy, 2018, 47,199-209, Bi doped LaFeO₃ (J. Mater. Sci., 2019, 54, 7460-7468)

However, a comparison of the crystallite sizes for different metal-doped LaFeO₃ was accomplished by analyzing the width of the (121) peak as shown Table 1, and it was determined that all of metal had doped into the LaFeO₃ structure due to the smaller crystallite size as compared to the undoped LaFeO₃.

2. All abbreviations present in the text should be explained, e.g., PL, DSR etc.

Reply:

All abbreviations have modified to full name when they present the first time.

3. Figure 6 - trend line should be presented only for positive values of Pr concentrations as it has no physical sense for negative ones.

Reply:

We change the trend line for positive values.

4. Figure 11 - meaning of violet and blue lines should be explained

Reply:

The meaniing of violet, blue and green lines in XPS are explained in the title of Figure 11.

5. line 79 - "effects ... was”

Reply:

This mistake has been modified.

 

Round 2

Reviewer 1 Report

From my opinion, the manuscript was not significantly improved compared to the first submission.

In the text, the authors indicate that the H₂ evolution rate is of 127 micromol h^-1 g^-1 using the Pr-doped LaFeO₃ photocatalysts. These performances are modest compared to other LaFeO₃ based photocatalysts (see the Table in the authors response). In this table, the authors indicate an H₂ evolution rate of 94.8 mmol h⁻¹ g⁻¹. This value is not in accordance with that indicated in the main text).

In the present state, I cannot recommend this manuscript for publication in Catalysts. The discussion must be strenghten and the authors must demonstrate the advances made compared to previous reports.

Author Response

Response to Reviewer 1 Comments

According to your suggestion, we have been modified the introduction, methods, results, and conclusions. Please see the red words in the text. And two comments of our reply shown in the following.

 

1. In the text, the authors indicate that the H₂ evolution rate is of 127 µmol h^-1 g^-1 using the Pr-doped LaFeO₃ photocatalysts. These performances are modest compared to other LaFeO₃ based photocatalysts (see the Table in the authors response). In this table, the authors indicate an H₂ evolution rate of 94.8 µmol h⁻¹ g⁻¹. This value is not in accordance with that indicated in the main text)

   Reply:

   Please accept our apologies to make a mistake for the H₂ evolution rate is 94.8 µmol h⁻¹ g⁻¹ in previous comments. We had been modified it, and this Table adds on page 14.

   Photocatalysts	Sacrificial agents	Cocatalyst	Light source	H2 evolution rate	Reference
   Pr-doped LaFeO3	20%TEOA solution	RhCrOx	350 W Xe lamp	127 µmol h−1 g−1	This work
   Rh-Doped LaFeO3	Glucose		UV-LEDs 10W, light intensity:57 mW/cm2) 375–380 nm	3822 μmol h-1g-1L-1	[1]
   Ru-doped LaFeO3	Glucose	-	UV-LEDs 10W, light intensity:57 mW/cm2) 375–380 nm	875 μmol h-1g-1	[2]
   LaFeO3	Glucose	-	UV-LEDs 10W, light intensity:57 mW/cm2) 375–380 nm	400 μmol h-1g-1	[3]
   Ru-LaFeO3/Fe2O3	Glucose		visible LEDs, 440 nm	1000 μmol h-1g-1L-1	[4]
   Nano LaFeO3	Ethanol solution	19μlPt	400 W tungsten light sources	3315 μmol h-1g-1	[5]
   Polyaniline-coverd LaFeO3	10%TEOA	3%Pt	300 W Xe lamp	92.4 μmol h-1	[6]
   Ternary LaFe0.8 / LaCu0.2 catalysts	12.5% HCHO solution		UV light (cut-off λ < 400 nm) 125W Xe lamp	250 μmol h-1g-1	[7]

    

   [1] Vaiano,V.; Iervolino,G.; Sannino, D. Enhanced photocatalytic hydrogen production from glucose on Rh-doped LaFeO₃, Chem. Eng. Trans., 2017, 60, 235-240.

   [2] Iervolino, G.; Vaiano,V.; Sannino, D; Rizzo, L.; Palma, V. Enhanced photocatalytic hydrogen production from glucose aqueousmatrices on Ru-doped LaFeO₃, Appl. Catal. B-Enviro. 2017, 207, 182–194.

   [3] Iervolino, G.; Vaiano, V.; Sannino, D.; Rizzo, L.; Ciambelli, P. Production of hydrogen from glucose by LaFeO₃ based photocatalytic process during water treatment, Int. J. Hydrog. Energy, 41, 2016, 959-966

   [4] Iervolino, G.; Vaiano, V.; Sannino, D.; Rizzo, L.; Galluzzi, A.; Polichetti, M.; Pepe, G.; Campiglia, P. Hydrogen production from glucose degradation in water and wastewater treated by Ru-LaFeO₃/Fe₂O₃ magnetic particles photocatalysis and heterogeneous photo-fenton, Int. J. Hydrog. Energy, 43, 2018, 2184-2196.

   [5] Tijare, S.N.; Joshi, M.V.; Padole, P.S.; Mangrulkar, P.A.; Rayalu, S.S.; Labhsetwar, N.K. Photocatalytic hydrogen generation through water splitting on nano-crystalline LaFeO₃ perovskite, Int. J. Hydrog. Energy, 13, 2012, 10451-10456.

   [6] Chen, Z.; Fan, T.; Zhang, Q.; He, J.; Fan, H.; Sun, Y.; Yi, X.; Li, J. Interface engineering: Surface hydrophilic regulation of LaFeO₃ towards enhanced visible light photocatalytic hydrogen evolution, J. Colloid Interface Sci. 2019, 536, 105-111.

   [7] Li, J.; Pan, X.; Xu, Y.; Jia, L.; Yi, X.; Fang, W. Synergetic effect of copper species as cocatalyst on LaFeO₃ for enhanced visible-light photocatalytic hydrogen evolution, Int. J. Hydrog. Energy, 2015, 40, 13918-13925.

2. In the present state, I cannot recommed this manuscript for publicationn Catalysts. The discussion must be strengthen and the authors must demonstrate the advances made compared to previous reports.

Reply:

We apologies again for the difficultly to compare our data to previous reports because the gas evolution rates depend on used different sacrificial agents, co-catalyst, light source, and the distance between light source and photocatalysts. Prof. Domen's group reported that the activities of photocatalysts to gas evolution rates in photocatalytic water splitting are extremely difficult to compare the activities measured in different reaction systems because of differences in the photocatalytic reactor systems and in the irradiance of different light sources. Thus, a measure of photocatalytic performance that is independent of the reactor and light source used is needed. The apparent quantum yield (AQY) or apparent quantum efficiency (AQE), can be used as a standard measure of activity.

Hisatomi, T.; Takanabe, K.; Domen, K. Photocatalytic water-splitting reaction from catalytic and kinetic perspectives, Catal. Lett., 2015, 145, 95-108.

Some previous reports used Pt as a cocatalyst, and we also used Pt cocatalyst and loading on Pr-LaFeO₃, which obtained lower H₂ evolution as shown in the following Figure. Therefore, the experimental results obtained that the samples with 0.5 wt.% RhCrO_x loading and 0.1 M of Pr doped LaFeO₃ calcined at a temperature of 700°C (0.1Pr-LaFeO3-700) exhibited the highest photocatalytic H₂ evolution rate of 127 µmol h⁻¹ g⁻¹, which is a higher 34% of photocatalytic H₂ evolution performance than undoped LaFeO₃ photocatalysts (94.8 µmol h⁻¹ g⁻¹).

We believe that the idealization of this study such as Pr doping and RhCrO_x loading on other LaFeO₃-based catalysts for previous reports increases their H₂ evolution rate at the same of their experimental environment.

 

 

 

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

The manuscript was improved by the authors and can be accepted by Catalysts.

The following corrections can be done at the proof stage :

• Figure 5 : (a) TEM-associated SAED pattern and (b) HRTEM image of ...
• Table 3 : photocatalyst