Facile Preparation of Highly Active CO₂ Reduction (001)TiO₂/Ti₃C₂T_x Photocatalyst from Ti₃AlC₂ with Less Fluorine

Round 1

Reviewer 1 Report

The authors have reported a novel facile synthesis method for (001)TiO2/Ti3S2 heterojunction and demonstrated the significantly high photocatalytic activity of their sample for CO2 reduction. The synthesis method and the analysis methods included in the manuscript seem appropriate. The authors' discussion seems consistent. There are enough characterizations in both the main manuscript and supplementary information. Therefore, I would recommend the publication of this manuscript in the "Catalysts" journal. I just suggest the authors consider the following issues:   

1) Titles in question form are not typically recommended in scientific publications. I suggest the author change the manuscript title.

2) The first six lines are not relevant to the abstract section and they are more relevant to the Introduction section. These 6 lines should be reduced to e.g. 1-2 lines.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this work, the authors proposed a method to synthesize (001)TiO2/Ti3C2 with a less fluorine ratio than that of the conventional synthesis of Ti3C2 MXene. More specifically, the HF etchant not only removes the Al layer from the Ti3Al2C MAX phase but also participates in the hydrothermal process to assist the growth of (001)TiO2. The prepared (001)TiO2/Ti3C2 showed better photocatalytic ability for CO2 reduction than conventional P25 catalyst which is attributed to the lower work function of Ti3C2 that suppresses the charge recombination. Although this knowledge is well-known, the method that the authors developed may be of interest to the researcher working in this field. I have several questions and concerns that the author can address

1.      Isn’t more dangerous to involve HF in hydrothermal reaction? Because HF undergoes critical condition (high pressure and high temperature), that may cause vapor evaporates into the air? How authors comment on this issue

2.      Why did F affect (001) surface plane formation?  Please explain in a more logical way, such as mentioning the affinity of F.

3.      MXenes dan their derivates can be synthesized in various ways according to this paper: https://doi.org/10.1016/j.mtener.2021.100864, author may mention the common method to synthesize MXene derivatives

4.      Why author did not include -OH groups in the Ti3C2 formula? It is clearly observed that Ti-OH exists based on the XPS result.

5. On page 6 lines 226-229, the author stated the reason why Ti3C2 can facilitate CH4 selectivity, without mentioning the reference. Please refer to any previous paper that works similarly

6. The concept of Schottky junction hole trapping has been shown in other photocatalytic work, please refer also to this paper https://doi.org/10.1016/j.seppur.2021.118815

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have all concerns addressed. The paper can be accepted in Catalysts.