STAINLESS STEEL/Fe-Co-Ni SEBAGAI ELEKTROKATALIS PADA REAKSI EVOLUSI HIDROGEN (Stainless Steel/Fe-Co-Ni as Electrocatalyst on Hydrogen Evolution Reaction)

ISANA SUPIAH YOSEPHINE LOUISE, Prof. Dra. Wega Trisunaryanti, M.S., Ph.D.Eng.

2014 | Disertasi | S3 Ilmu Kimia

Sifat-sifat stainless steel memungkinkan dimanfaatkan sebagai elektroda, tetapi perlu diupayakan peningkatan efektivitas katalitiknya. Oleh karena itu perlu dilakukan pelapisan dengan logam yang bersifat katalitik, seperti Fe, Co dan Ni pada substrat stainless steel. Logam-logam Fe, Co dan Ni selain bersifat katalitik juga memiliki ukuran relatif sama, sifat-sifat mirip, mudah diperoleh dan relatif murah. Preparasi dan karakterisasi stainless steel/Fe-Co-Ni sebagai elektrokatalis pada reaksi evolusi hidrogen telah dipelajari. Penelitian ini bertujuan memperbaiki sifat stainless steel sebagai elektroda pada elektrolisis air sehingga memiliki aktivitas katalilitik terhadap reaksi evolusi hidrogen. Stainless steel/Fe-Co-Ni dibuat melalui pelapisan substrat stainless steel dengan logam tunggal Fe, Co dan Ni, komposit logam biner Fe-Co, Fe-Ni dan Co-Ni, dan komposit logam terner Fe-Co-Ni, menurut metoda voltametrik linear dengan menggunakan elektroda kerja stainless steel, elektroda pembanding Ag/AgCl dan elektroda kontra platinum. Elektroda terner dibuat dengan memvariasi kandungan Fe (stainless steel/Fe1-5-Co-Ni). Karakter stainless steel ditentukan dengan scanning electron microscopic-energy-dispersive Xray spectroscopy (SEM-EDX), optical emmision spectrometer (OES), voltametri dan gas sorption analyzer (GSA). Karakter elektroda tunggal dan biner ditentukan dengan SEM dan voltametri. Karakter elektroda terner dianalisis dengan SEM-EDX, voltametri dan GSA. Elektroda tunggal, biner dan terner digunakan sebagai elektroda pada reaksi evolusi hidrogen dengan cara elektrolisis air dalam suasana basa dengan penambahan NaHCO3 sebanyak 1 - 5 gram per liter air. Hasil penelitian menunjukkan bahwa elektroda stainless steel/Fe-Co-Ni: tunggal, biner dan terner dapat dibuat dengan metoda voltametri linear. Hasil analisis EDX dan OES stainless steel menunjukkan kadar Fe = 80-82%, Co = 0,03-0,05% dan Ni = 0-0,31%. Hasil GSA menunjukkan luas muka spesifik, volume pori total dan jejari pori stainless steel masing-masing sebesar 6,628 m2/g, 0,011 cc/g dan 32,836 Ã…. Data voltametri menunjukkan belum terjadi elektrodeposisi logam Fe, Co dan Ni, karena signal oksidasi dan reduksi masih lemah, yang diperkuat dengan data morfologi SEM yang belum muncul bercak-bercak. Hasil analisis voltametri elektroda tunggal, biner dan terner menunjukkan telah terjadi elektrodeposisi logam Fe, Co dan Ni pada substrat stainless steel karena munculnya signal oksidasi dan reduksi yang signifikan, yang diperkuat dengan data morfologi SEM dengan munculnya bercak-bercak. Hasil analisis EDX menunjukkan kadar Fe pada elektroda stainless steel/Fe(1-5)-Co-Ni sebesar 57,09-74,71%. Data GSA menunjukkan bahwa luas muka spesifik elektroda terner lebih besar dibandingkan stainless steel. Elektroda terner memiliki aktivitas katalitik lebih baik untuk reaksi evolusi hidrogen dibandingkan tunggal dan biner. Elektroda tunggal dan biner tidak selalu bersifat katalitik terhadap reaksi evolusi hidrogen. Reaksi evolusi hidrogen paling baik dengan penggunaan elektroda stainless steel/Fe1-Co-Ni dengan penambahan 5 gram NaHCO3 (yakni 32,28 kali lebih baik bila dibandingkan dengan stainless steel, serta 1,9 dan 1,6 kali lebih baik bila dibandingkan elektroda tunggal dan biner).

The properties of stainless steel are possible to be used as electrode in the other hand its catalytic activity needs to be increased. Hence it’s necessary to be coated with metals which have catalytic properties, i.e. Fe, Co and Ni on stainless steel substrate. Fe, Co and Ni metals do not only have catalytic activity but also have the same size, identical properties, abundance and inexpensive. The preparation and characterization of stainless steel/Fe-Co-Ni has been studied for electrocatalyst of hydrogen evolution reaction. The purpose of the research is improving the properties of stainless steel as electrode of water electrolysis to have catalyst activity for hydrogen evolution reaction. The stainless steel/Fe-Co-Ni electrodes were prepared by coating the stainless steel substrate with singular Fe, Co, and Ni metals, binary Fe-Co, Fe-Ni, and Co-Ni composites, and ternary Fe-Co-Ni composites, using linear voltammetric method with stainless steel as working electrode, Ag/AgCl as reference electrode and platinum as counter electrode. The ternary electrodes were prepared under the variation of Fe content (stainless steel/Fe1-5-Co-Ni). The stainless steel characters were determined by scanning electron microscopic-energy-dispersive X-ray spectroscopy (SEM-EDX), optical emmision spectrometer (OES), voltammetric and gas sorption analyzer (GSA). The characters of the singular and binary electrodes were determined by SEM and voltammetric methods; and the ternary were analyzed by SEM-EDX, voltammetric, and gas sorption analysis (GSA) methods. Those electrodes were used for hydrogen evolution reaction by water electrolysis in basic condition with 1-5 g of NaHCO3 in a litre of water. The result showed that the stainless steel/Fe-Co-Ni electrodes: singular, binary and ternary could be prepared by linear voltammetric method. The EDX and OES analysis shown that the stainless steel contains Fe = 80-82%, Co = 0.03-0.05% and Ni = 0-0.31%. The GSA analysis shown that specific surface area, pore volume and pore radius of stainless steel were found to be 6.628 m2/g, 0.011 cc/g and 32.836 Å respectively. The voltammogram of the stainless steel indicates that electrodeposition of Fe, Co and Ni metals was not occured, because of the weak oxidation and reduction signal, being confirmed also by the SEM image without spot. The voltammogram of singular, binary and ternary electrodes indicate that Fe, Co and Ni metals were electrodeposited onto the stainless steel substrate shown by the significant oxidation and reduction signal, that convinced also by the SEM image stainless steel/Fe(1-5)-Co-Ni electrodes was found to be 57.09-74.71%. The GSA analysis shown that specific surface area of the ternary electrodes was greater than that of the stainless steel. The ternary electrode shown the best performance compared to those of the singular and binary electrodes. The singular and binary electrodes did not always show catalytic activity on hydrogen evolution reaction. The catalytic activity of the ternary electrodes were found to be higher than that of the singular and binary. The highest hydrogen electrogenerated was produced by the stainless steel/Fe1-Co-Ni added with 5 g of NaHCO3 (it is 32.28 times greater than that of the stainless steel, and 1.9 and 1.6 times greater than that of the singular and binary).

Kata Kunci : stainless steel, elektroda, elektrodeposisi, reaksi evolusi hidrogen, elektrokatalis