1279 J. Indian Chem. Soc., Vol. 94, December 2017, pp. 1279-1290 Theory of chronocoulometry of a pseudo first-order catalytic process at a rough electrode † Md. Merajul Islam and Rama Kant* Department of Chemistry, University of Delhi, Delhi-110 007, India E-mail : rkant@chemistry.du.ac.in Manuscript received 25 October 2017, accepted 01 November 2017 Abstract : A theoretical model for single potential step charge-transients has been developed for the pseudo first-order catalytic coupled (EC’) reaction mechanism at rough electrode-electrolyte interface. A second-or- der perturbation solution in surface prole for an arbitrary rough surface is obtained. The expression for the charge-transient at the rough electrode-electrolyte interface for band limited self-affine fractal roughness is obtained. An extension of the generalized Danckwerts’ expression in terms of the charge is presented. Our results show an enhancement in the charge-transients due to the roughness present at the electrode surface. The morphological characteristics show strong dependency in the anomalous intermediate regime obtained from the power-spectrum of roughness while the long-time regime is the time dependent kinetic controlled. The traditional plot of charge-transient does not provide the information related to the morphology and its pos- sible kinetic influences. Keywords : Power spectrum of roughness, fractal electrode, Chronocoulometry, catalytic process, charge transfer. Introduction The surface morphology or roughness of an elec- trode affects the spectroelectrochemical responses. The roughness effect is inevitable especially, if the elec- trodes are made of solid materials. The rough elec- trodes have potential to be used in fundamental and applied fields 1–6 . This is possible because rough sur- faces show enhanced surface reactions due to the in- crease in the effective area. Rough surface is also capable to separate electrons and holes from combi- nation because of generation of channel-like structure in the vicinity of the electrode. Hence, rough elec- trode surface structure is favorable to enhance the performance of light emitting diodes and solar cell devices 1 . In our previous paper, we have generalized the Anson equation that describes the potentiostatic re- sponse of a reversible charge transfer reaction for † Acharya J. C. Ghosh Memorial Lecture (2016). rough electrode. It explains the observed deviation in the Anson plot from linearity due to the roughness present at the electrode surface 7 . An important reac- tion mechanism is where the electrochemical step is coupled with bulk kinetics which is the catalytic coupled reaction mechanism used in many fundamen- tal as well as in applied fields 8–10,12–21 . Saveant et al. 9 discussed the potentiostatic and cyclic voltammetric responses of this mechanism through various zones attributing to the extent or reversibility of the E step as well as the dependence of the re- sponse on the concentration of the electrochemically inactive species. Here, we focus on the influence of ubiquitous electrode roughness on the response of such pseudo first-order catalytic coupled reaction mecha- nism under the potentiostatic perturbation. The pseudo first-order catalytic-coupled (EC’) re- action mechanism scheme is one of the most impor-