Reinardo Ramawijaya Widakusuma, Fathir Azzaki Iradata, Mokhamad Ali Rizqi Maulana, Ikhwan Nur Rahman

Electrodeposition of Thin Film Cu-Zn-Sn Alloy for Water Splitting Application

Introduction

Electrodeposition of thin film cu-zn-sn alloy for water splitting application. Explore electrodeposited Cu-Zn-Sn (CZT) alloys for water splitting. This study details their catalytic activity in hydrogen & oxygen evolution and optimized H2 production.

Abstract

An energy transition to renewable energy sources is necessary due to the scarcity of fossil fuels and their detrimental effects on the environment. Water splitting process is one of the practical and effective way that does not occur spontaneously. This study investigates catalytic activity of Cu-Zn-Sn (CZT) photocatalyst in hydrogen evolution and oxygen evolution reaction. The CZT deposited with varied electrolyte’s pH of 6 and 9 on indium tin oxide substrate at the room temperature for 600 seconds. According to the X-ray diffraction patterns, there were Cu6Sn5, Cu5Zn8, and Sn metal phases with monoclinic, cubic, and cubic crystal systems. The scanning electron microscopy technique results of all CZT alloy sample showed a dense, non-uniform, and polycrystalline surface structure. The CZT alloys were found to have an average particle size of 0.35 μm. CZT alloys can produce a photocurrent density of 0.19 mA/cm² at a potential of 1.29 V vs RHE. the charge transfer resistance of CZT synthesized at pH 6 is lower (21.48 Ω) compared to pH 9 (28.36 Ω). The Tafel slope of HER for pH 9 CZT was -133 mV/dec, which was lower than that of pH 6 CZT (-88 mV/dec), indicating faster H2 production and corrosion resistance on pH 9 CZT.

Review

This study presents an investigation into the electrodeposition and catalytic activity of Cu-Zn-Sn (CZT) alloy thin films for water splitting applications, addressing the critical need for renewable energy solutions. The authors successfully electrodeposited CZT films on indium tin oxide (ITO) substrates at room temperature, exploring the impact of electrolyte pH (6 and 9) on the resulting material properties and electrochemical performance. The chosen approach of exploring a ternary alloy like CZT, which can form various intermetallic phases, for both hydrogen and oxygen evolution reactions is relevant, contributing to the search for earth-abundant and efficient electrocatalysts. Structural characterization revealed the presence of Cu6Sn5, Cu5Zn8, and Sn metal phases with monoclinic and cubic crystal systems, respectively, indicating a complex multiphase composition. Scanning electron microscopy confirmed a dense, non-uniform, and polycrystalline surface with an average particle size of 0.35 µm for all CZT samples. Electrochemically, the materials demonstrated a photocurrent density of 0.19 mA/cm² at 1.29 V vs RHE. Interestingly, the charge transfer resistance was lower for CZT synthesized at pH 6 (21.48 Ω) compared to pH 9 (28.36 Ω). However, the interpretation of the Tafel slope for HER requires careful re-evaluation: while the abstract states that the Tafel slope for pH 9 CZT was -133 mV/dec, which was "lower" than pH 6 CZT (-88 mV/dec) "indicating faster H2 production," in electrochemistry, a *smaller absolute value* of the Tafel slope typically indicates faster reaction kinetics. Therefore, a Tafel slope of -88 mV/dec (pH 6) would generally suggest faster HER kinetics than -133 mV/dec (pH 9). This discrepancy in interpretation needs to be addressed. Overall, the work provides a foundational exploration into the synthesis and initial electrochemical performance of CZT alloys for water splitting. While the methodology for electrodeposition and material characterization is clearly outlined, the study could benefit from a more thorough analysis of its electrochemical data, particularly regarding the Tafel slope interpretation. Furthermore, a more comprehensive discussion of the photo-activity (e.g., specific wavelength dependency, incident photon-to-current efficiency) would be beneficial, especially given the use of the term "photocatalyst." Future work should focus on optimizing the deposition parameters beyond pH, improving the catalytic performance, providing comparative data with existing catalysts, and critically, conducting long-term stability tests, which are crucial for practical water splitting applications. Clarifying the performance for OER, which is mentioned in the abstract's scope but not elaborated in the results, would also strengthen the study.

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