(Digital Presentation) Oxygen Evolution Activity and Durability on Mn Oxide-Based Catalyst in Acidic Solution
Authors: Matsuzawa Koichi , Kohara Yuma , Ishihara Akimitsu 
Published: December 2024

On Sep. 25, 2023, Hydrogen energy ministerial meeting (H2 EM 2023) was held by the ministry of economy, trade and industry (METI) of Japanese government as online special event with cabinet members and officials from 23 countries, regions, and organizations. Participants shared the additional global goals to increase hydrogen demand which could potentially reach 150 million ton by 2030, with up to 90 million ton being demand for renewable and low-carbon hydrogen. In the chair’s summary of meeting, 0.7 Mt of H2 production with 700 MW of electrolyser installed as of 2022 [1-2].

Proton exchange membrane water electrolysis (PEMWE) has already commercialized and recently applied its system for the Power-to-Gas (PtG) all over the world. In Kofu City in Yamanashi, Japan, the Komekurayama facilities has demonstrated the Power-to-Gas (P2G) system such as system of the intermittent generated electricity from the solar 10 MW generator and transform it to hydrogen using a PEMWE electrolyser of 1.5 MW capacity [3]. However, the cost of Ir metal as uses for material of anode has been raising in these two years, and it is almost 4 times higher than that of platinium in Japan [4-5]. From this point of view, the alternative anode with high durability should be required for the production of Green Hydrogen [6]. The catalytic activity of magnesium oxide has applied and studied in acidic solution [7-8] and we have also Mn oxide-based film fabricated by sputtering procedure for oxygen evolution reaction (OER) [9-10]. In this study, we have investigated the OER activity of Mn Oxide-based electrocatalysts as particle fabricated by thermal decomposition.

MoO2 was prepared on Ti rods as a substrate. The 4 M Mn(NO3)26H2O aqueous solution was used as precursor. It dropped on substrate, and the thermal decomposition was demonstrated at 220 oC for 1 h. The loading amounts of MoO2 was constant at 1.1 mg cm-2. thickness of ZrO2 film was 10 nm for preparation. We used conventional three electrode cell with each sample as working electrode while the reversible hydrogen electrode (RHE) and carbon plate were used as reference and counter electrode to demonstrate the electrochemical measurement in 1 M H2SO4 solution with saturated nitrogen atmosphere at 303 K. Several samples were demonstrated pretreatment from 0.05 to 1.2 V vs. RHE before the measurement of OER. The slow scan voltammetry was performed from 1.2 to 2.0 V to evaluate the OER activity.

Figure 1 shows polarization curves of OER on MoO2 on Ti substrate (MnO2(TD)/Ti). For the comparison, Mn-TaOx on Ti fabricated by sputtering procedure (Mn-TaOx(Sputter)/Ti) in our previous study [10] also shows in Fig. 1. The vertical axis was shown by the geometric current density (i
geo). The i
geo at 2.0 V of MnO2(TD)/Ti was ca. 200 mA cm-2 and it was so much larger than that of Mn-TaOx(Sputter)/Ti because the shape of MnO2(TD)/Ti as particle was different from that Mn-TaOx(Sputter)/Ti as thin film. The i
geo of MnO2(TD)/Ti was also similar to that of MnO2(TD)/FTO [8]. Tafel plots of OER on MnO2(TD)/Ti was 115 mV dec-1 while that of Mn-TaOx(Sputter)/Ti was 62 mV dec-1.

Acknowledgement: This work is partially supported by JFE 21st Century Foundation.

Reference

https://www.meti.go.jp/english/press/2023/0925_002.html

https://www.meti.go.jp/press/2023/09/20230925002/20230925002-1.pdf

https://centromariomolina.org/wp-content/uploads/2022/06/Green-Hydrogen-CMM.pdf

https://furuyametal.jp/english/fmbi/chart/?language=en

https://gold.tanaka.co.jp/commodity/souba/d-platinum.php

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Figure 1