Hierarchical three-dimensional copper selenide nanocube microelectrodes for improved carbon dioxide reduction reactions

The design of high-performance and earth-abundant electrocatalysts for electrochemical carbon dioxide (CO2) reduction reactions (CO(2)RRs) to form fuels and value-added chemicals offers an emergent solution for environmental and sustainable energy issues. Herein, we report a facile and one-step electrochemical fabrication of a series of hierarchical three-dimensional (3-D) copper selenide nanocubes (CuSe NCs) assembled as domain nanocube-, branched nanocube-, and dendrite nanocube-like surface morphologies on copper microelectrodes (CuMEs). Our results reveal that the peculiar morphology-controllable CuSe NCs are grown on a Cu microelectrode surface due to the preferential diffusion of Cu and Se ions and deposition as CuSe heterostructures. The as-developed CuSe NCs are employed as potential electrocatalysts for electrochemical CO(2)RRs in both 1.0 M KHCO3 and 0.1 M 1-butyl-3-methyl-imidazolium hexafluoro-phosphate ([Bmim]PF6) in acetonitrile (MeCN) electrolytes. The as-developed CuSe NCs-B|CuMEs exhibited a less negative onset potential (similar to 0.5 V (RHE) in 1.0 M KHCO3 and similar to 1.1 V (Ag/AgCl) in 0.1 M [Bmim]PF6/MeCN) and high cathodic current density (similar to 120.3 mA cm(-2) @ -1.3 V (RHE) in 1.0 M KHCO3 and similar to 23.4 mA cm(-2) @ 2.0 V (Ag/AgCl) in 0.1 M [Bmim]PF6/MeCN). The CuSe NCs-B|CuMEs showed a low cathodic potential of similar to 0.65 V vs. RHE (1.0 M KHCO3) and similar to 1.6 V vs. Ag/AgCl (0.1 M [Bmim]PF6/MeCN) to attain similar to 10 mA cm(-2), small polarization resistance, high mass activity, and long-term durability. The attained high electrocatalytic performance of the CuSe NC-based Cu microelectrodes is due to high crystallinity, hierarchical 3-D nanocube-like morphology, a large volume of electrochemical active sites, low polarization resistance, and integrated intrinsic catalytic activity.