Morphology Modulation on Boron-Doped Diamond Electrodes and Its Effect on Boosting the Conversion of CO2-to-CO

Boron-doped diamond (BDD) electrodes have achieved excellent selectivity and switchable product formation for electrochemical CO2 reduction reaction (eCO2RR), although the current should be improved. Surface morphology modulation is a promising approach for improving it by exposing a larger electroactive area. Herein, we fabricated a porous 1 % BDD film (p-BDD) and a rough-surfaced 1 % BDD film (r-BDD) by modifying the surface of a flat 1 % BDD film (f-BDD). Fundamental electrochemical properties, including potential window, differential capacitance, and active area were examined, followed by eCO2RR activity evaluation. The synthetic r-BDD electrode enabled approximately 1.7-fold increases in current density and yield rate (17.6 & mu;mol h-1) toward CO production compared to f-BDD (10.3 & mu;mol h-1). This improvement in eCO2RR is ascribed to the larger electroactive area with a comparable kinetic performance, in comparison to f-BDD. On the other hand, p-BDD possesses the largest real area, but showed the lowest activity for eCO2RR (1.2 & mu;mol h-1 for CO), which could result from hindered diffusion of CO2 inside the pores. X-rays photoelectron spectroscopy and electrochemical impedance spectroscopy were employed to disentangle the morphological structure effect from the chemical reactivity of the electrode surface.