Amperometric Oxygen Sensor Based on Bimetallic Pd-Cu/C Electrocatalysts

Round 1

Reviewer 1 Report

In the manuscript there are many severe errors, starting with the abstract and introduction where is not clear if the studied alloy is a Pt-Cu alloy or a Pd-Cu alloy. The approached subject is not new and several important references are not considered, such as:

•  Bimetallic Pd–Cu Oxygen Reduction Electrocatalyst, Journal of The Electrochemical Society 2008, 155(6):B602-B609
• PdCu Nanoalloy Electrocatalysts in Oxygen Reduction Reaction: Role of Composition and Phase State in Catalytic Synergy, ACS Appl. Mater. Interfaces 2015, 7, 46, 25906–25913
  

Chapter  3.  Materials and Methods Discussions is totally unclear regarding the catalyst preparation, electrocatalyst enhancement and O₂ sensor. The electrochemical  detection of O2 should be  studied using also the linear sweep voltammetry using a rotating disk electrode. There  are  big misunderstandings  related  to the "oxidation rate of O₂". Overall,  English is very bad and is really difficult to  understand the text.    

Author Response

1. On page 1 and page 2 the abstract and introduction were revised with red-colored highlight in the following

Abstract

Laminated Pd-Cu alloy/C/Nafion multilayer … as the candidate electrodes.

According the phase identification … on the Pd site.

A successive response … sensitivity decay.

Introduction

These alloyed metal doesn’t …its electrocatalysis efficiency [6].

Prior to proceeding measurement, we …closely with the electrochemistry.

We also cite these two paper as references [12] and [120] on page 2:

In addition, Wu … for oxygen reduction [12].

On page 8: The Pd6Cu4 electrode shows … the ORR intrinsic property [20].

 

2. On page 10, the Materials and Methods Discussions were revised with red-colored highlight in the following :

3.2. Preparation for the catalyst of electrochemical reaction

The former solution, PdCl₂ solution, … with a concentration step, 10 %, sequentially.

These as-titrated slices …proceed with alloying.

Reviewer 2 Report

In this article, the authors reported metal-air electrodes with a Pt-Cu alloy/C/Nafion structure as electrochemical sensor for O2. This work is nicely written and presented. All the results are convincing. I would recommend this for publication as it is.

Thank you

Author Response

Thank you for your positive comment.

Reviewer 3 Report

This work is interesting, but the way it is presented needs to be significantly improved to make the manuscript publishable in Catalysts. Firts of all, Cu is dopant, it will dope Pd, the English language should be extensively corrected because this reviewer has the impression that the description of the experiments and interpretation of the results is rather due to a poor English thatn a scientific misunderstanding. For example, on Page 3 is stated "the more Cu was doped in the electrode" and on Page 4 is written "of the doped Cu". Doped is Pd, not Cu, which is the dopant. On Page 3, the interpretation of the powder X-Ray diffractogram, relative to the 2nd peak of Pt it is stated that: "the latter implied segregation from the Pd-Cu alloy to form a Pd-ricjh overlayer". This statement is purely speculative since no experoimental evidence is brought to support it. It will be very useful to add the reference XRD patterns to the graph, to compare them with the experimantal data. On Page 4 "oxidization" should read "oxidation". On the same page, the interpretation fof the XPS spectra state that " the intensity ratio of Cu2O to Cu in Pd6Cu4 is less than that in Pd8Cu2 and Pd5Cu5. This is due to the highest oxidation PdO3 appearing in the..". It is not clear how the higher oxidation number of Pd can be deduced from the Cu2O/Cu ratio in these plots. On Page 6 "stat" should read "state". BAsed upon the foregoing, I recommend that the changes indicated above be perfromed in order to make this manuscript amenable to publication in Catalysts.

Author Response

On page 4 and page 5 the manuscript was revised with red-colored highlight in the following

2.1. Microstructure Investigation of the Electrodes  

The more the Cu … the Pd-Cu electrode oxidized. The former shows a sharp … than the Pd-Cu alloy [13].

This suggests … of Pd texture.

In contrast to the aforementioned results … reconfirming the previous results.

The Pd oxide increased … increase of Cu composition.

The Cu XPS proved … to facilitate oxidation.

In contrast, no Cu-related peak …, i.e. indirect Cu oxidation [6].

Round 2

Reviewer 3 Report

The authors addressed most of the reviewers'c comments and suggestions and the manuscript is now suitable fro publication in Catalysts.