Fabricating Dispersed Fine Silver Nanoparticles on Liquid Substrate for Improved Photocatalytic Water Splitting Efficiency

Round 1

Reviewer 1 Report

Comments to the Author
The author has been reported the photoelectrocatalytic performance of silver NPs prepared on a silicone oil surface and transferred to a strontium titanate crystal (STO) by thermal vaporization. The paper is well written, but there are some major flaws in the manuscript that should be addressed, as listed below. 

1.      In fact, your introduction was well-written. However, it would be great if you could compare the present results with those in the literature. Please define clearly what makes your paper superior to other similar papers (both in the abstract and in the introduction).  A number of related papers could be cited, (10.1016/j.ijhydene.2020.10.148., 10.1016/j.apsusc.2017.05.074., 10.3390/nano13050920., 10.1016/j.ceramint.2018.03.017., and 10.3390/nano9101502).

2.      Figure 1 need to be reconstructed and captions must be revised accordingly in the manuscript. Author must confirm the XRD card number (JCPDS) for both STO, and Ag NPS.

3.      The SEM, and /or TEM analysis and particle-size distribution profiles of the Ag NPs/STO catalyst must be presented, as these will largely influence applicative electrochemical PEC catalytic properties.

4.       1. "More importantly, it must be validated that the level of the Ag NPs loading depends mainly on the fabricated electrode's morphological features, time, and methodology of Ag NPs decoration." It is recommended to supplement the physicochemical characterization of the Ag NPs decorated STO photoanode with varied Ag NPs loading by varying the duration of deposition process in SI.

5.      For comparison, the potential - current curve for a bare STO is presented in Fig. 3(b). Please carefully check these data.

6.      Please provide characterization data after long-term testing, including but not limited to SEM, XRD, etc.

7.      The format of words in Figures should be consistent, including the font size, sample name, etc.

There are many errors in the paper, so the Author is encouraged to review the form and the English of the manuscript.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The article reports the synthesis and transfer of Ag nanoparticles onto STO crystal. Photoelectrochemical measurements were conducted to demonstrate the enhanced photocatalytic efficiency induced by the presence of Ag nanoparticles. It was observed that the current density increases as the deposition temperature of the nanoparticles increases from 253 K to 333 K, resulting in an improvement of the crystallinity of the nanoparticle structure. However, when the temperature is further increased up to 353 K, a reduction in the current density is observed. The author attributes this phenomenon to a change in the growth model of the nanoparticles, which start to overlap with each other, increasing the distance between the nanoparticles and the STO substrate. As a result, the efficiency of charge transfer between the nanoparticles and the underlying STO surface decreases.

This work can be published only if the following aspect are addressed:

1) The nanoparticles were grown on frosted glass covered with oil and then transferred onto the STO crystal. The author claims that the NPs attach firmly to the STO simply by gently placing the sample surface on it. This appears to be a very straightforward process. How do the nanoparticles bind to the STO, and why do they adhere so well without any specific treatment? Additionally, the author mentions that the oil is removed by washing with acetone. In this process, is there no risk of the nanoparticles being washed away? What kind of chemical bonding occurs between the NPs and the STO through mere contact? This step seems quite unusual to me. Could the author provide some additional references where the same approach is used to transfer nanoparticles from one substrate to another?

2) Can the author clarify the advantage of using an oil film to synthesized Ag NPs?

3)The author could include SEM images in Figure 2 and/or Figure 5 with the same scale to verify if the overlapping growth of nanoparticles indeed occurs only at high temperatures. This aspect needs to be clarified as it is a crucial measure that supports the author's hypothesis to justify the reduced photocatalytic efficiency when using growth temperatures higher than 333 K.

Some typos should be corrected:

• Remove "is dominantly" in line 11 of the abstract.
• Correct "potentialstat" to "potentiostat" in line 11.
• In line 173, it should be Fig. 3a instead of 3b.
• Replace "synthesis" with "synthesized" in line 278.
• Change the inset figure 3 as "dependent behavior for the relative current density jr as a function of the substrate temperature T."

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The author has successfully addressed all the comments. Moreover, the author has made significant changes in the manuscript to fulfill the reviewer's requirement. I feel the revised manuscript is now well-readable and eligible to be published in this journal.

Reviewer 2 Report

The author addressed all my questions and modified the manuscript according to reviewers' suggestions. No further changes are required.