Malaysian Journal of Analytical Sciences Vol 23 No 1 (2019): 52 - 59

EFFECT OF DEPOSITION TIME ON STRUCTURAL AND CATALYTIC PROPERTIES OF Pt FILMS ELECTRODEPOSITED ON Ti SUBSTRATE

(Kesan Masa Enapan Terhadap Sifat-sifat Struktur dan Katalitik bagi Filem Pt Dielektroenapan di atas Substrat Ti)

Siti Norsafurah Ab Malek and Yusairie Mohd*

Faculty of Applied Sciences,

Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia

*Corresponding author: yusairie@salam.uitm.edu.my

Received: 13 April 2017; Accepted: 17 April 2018

Abstract

Platinum (Pt) films were prepared on Titanium (Ti) surface at various deposition times ranging from 30 to 90 minutes using the electrodeposition technique. The morphology of the Pt films was determined using field emission scanning electron microscope (FESEM). Furthermore, the electrocatalytic activity of the prepared Pt films towards methanol oxidation in alkaline medium was investigated using cyclic voltammetry. The surface morphology changed with different deposition times from less compact durian-like structure at shorter times (< 60 minutes) to more compact durian-like structure at longer times (> 60 minutes). The loading amount and surface coverage of Pt on the Ti surface were increased as the deposition time increased. The calculated values of electrochemically active surface area (ECSA) for the Pt films were increased with increasing deposition time as evident in 30 minutes (6.54 m² g^-1), 45 minutes (7.34 m² g^-1) and 60 minutes (8.08 m² g^-1). Nevertheless, the ECSA value dropped to 7.70 m² g^-1 for longer deposition time (90 minutes). This may be caused by the coagulation of the Pt centres with the growth of neighbouring centres, which decreasing the available active surface area on the films. This film also demonstrated the highest stability for methanol oxidation reaction (MOR) in alkaline medium with the result of 5.18 mA cm^-2 at 1 hour.

Keywords: Pt films, deposition time, methanol oxidation, alkaline medium

Abstrak

Filem Platinum (Pt) telah dienapkan ke atas titanium (Ti) untuk jangka masa yang berbeza dari 30 sehingga 90 minit menggunakan teknik elektroenapan. Morfologi filem Pt telah ditentukan menggunakan medan pancaran imbasan elektron mikroskop (FESEM). Tambahan lagi, aktiviti filem Pt terhadap pengoksidaan metanol dalam medium beralkali telah disiasat menggunakan voltammetri berkitar. Morfologi filem Pt telah berubah daripada kurang padat struktur durian (< 60 minit) kepada struktur durian yang lebih padat pada masa pengenapan Pt yang lebih lama (>60 minit). Jumlah muatan dan liputan permukaan filem Pt di atas permukaan Ti telah bertambah dengan penambahan masa enapan. Nilai-nilai kiraan kawasan permukaan aktif secara electrokimia (ECSA) untuk filem-filem Pt telah bertambah dengan pertambahan masa enapan seperti dibuktikan dalam 30 minit (6.54 m² g^-1), 45 minit (7.34 m² g^-1) dan 60 minit (8.08 m² g^-1). Walaubagaimanapun, nilai ECSA telah jatuh ke 7.70 m² g^-1 bagi masa enapan yang lebih lama (90 minit). Ini mungkin disebabkan oleh pengumpalan pusat-pusat Pt dengan ketumbuhan pusat-pusat sekitaran di mana ini mengurangkan kawasan permukaan yang aktif sedia ada atas filem tersebut. Filem ini juga telah menunjukkan kestabilan tertinggi untuk tindak balas pengoksidaan metanol (MOR) dalam medium beralkali dengan keputusan 5.18 mA cm^-2 pada 1 jam.

Kata kunci: filem Pt, masa enapan, pengoksidaan metanol, medium beralkali

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