Discerning the oscillatory electrochemical response during electrodeposition of cobalt in the presence of but-2-yne-1,4-diol

Insights into Chemical Changes Causing Transient Potential Patterns during Cobalt Electrodeposition: An Operando SHINERS Investigation

“…7,8 Although electrodeposition is a simple method for Co thin film deposition, often anomalous transient potential oscillatory patterns were observed in the presence and absence of organic additives. 9−13 Similar oscillations have been observed in Cu 12,14,15 and Co 10,16 electrodeposition. Butynediol (2butyne-1,4-diol) is a widely used class II brightener in metal and alloy electrodeposition.…”

“…17−19 We have also observed a facilitated hydrogen adsorption and evolution along with Co 2+ reduction at low overpotentials in the presence of butynediol, which leads to the potential oscillations. 16 The chemical changes due to local physicochemical environment are the key factor for the resulting morphology, which can be controlled by the addition of surface active agents, viz., organic additives. 20 Therefore, understanding the detailed mechanistic role of an additive through intermediate species in electrodeposition can help rational selection.…”

“…The typical cyclic voltammogram of Co electrodeposition in the presence of butynediol is shown in Figure 2b, along with a potential-dependent operando SHINERS spectrum. Addition of butynediol introduces additional reduction features (Figure S3), in agreement with our previous report, 16 which was imputed for complex interfacial reactions involving electrodeposition of cobalt, co-deposition of hydrogen, and adsorption of butynediol on cobalt. Although co-deposition of hydrogen is the main cause of these features, the Co−H modes (around 1950 cm −1 ) 35 are not observed in the Raman spectra due to the presence of butynediol (Figure S5).…”

“…As explained in our previous report along with others, the diminishing pattern could be fairly imputed to the size effect. 16 The surface coverage by hydrogen decreases with an increase in Co particle size. 38 This eventually decreases the amplitude of potential oscillation and form steady-state oscillations beyond a critical size.…”

“…Interestingly, two distinct oscillations were observed in this study, the earlier one with diminishing and the latter with an emerging trend. As explained in our previous report along with others, the diminishing pattern could be fairly imputed to the size effect . The surface coverage by hydrogen decreases with an increase in Co particle size .…”