Understanding Synergism of Cobalt Metal and Copper Oxide toward Highly Efficient Electrocatalytic Oxygen Evolution

• Published in: ACS catalysis 2018-12, Vol.8 (12), p.12030-12040
• Main Authors: Niu, Wenhan, Shi, Jianjian, Ju, Licheng, Li, Zhao, Orlovskaya, Nina, Liu, Yuanyue, Yang, Yang
• Format: Article
• Language: English
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.8b03702

Understanding the synergism of bimetallic transition metal (TM)-based catalysts for oxygen evolution reaction (OER) is very difficult because it is complicated to identify the surface active sites in a bimetal system. Herein, we rationally designed Cu oxide (CuO x ) nanoarray film (NF) as an example to investigate the synergism and doping effects of iron group metals on OER. This is an advantage because CuO x is electrocatalytically inert and oxidatively stable, which is much better than carbon-based platforms. Especially, cobalt (Co) shows a much stronger synergism as compared with nickel (Ni) and iron (Fe). By introducing Co into the inert CuO x NFs, the Co active sites can be correlated to the OER activity by rationally regulating the morphology of CuO x NFs. In addition, the phase transformation from Cu2O to CuO occurs during the OER testing, further boosting the OER activity of Co-doped CuO x NF due to the hybridization change of Co active site. As a result, the Co-doped CuO x NF with 0.30 at. % Co (denoted as Co0.30CuO x ) shows a remarkable OER activity (an overpotential of 0.29 V at 10 mA cm–2) in basic solution, superior to those of the state-of-the-art OER catalysts. Both experimental and computational studies indicate that the introduction of Co-dopant in CuO x changes the rate-limiting step from M-OHads → M-Oads to M-Oads → M-OOHads and decreases the theoretical onset potential by 0.31 V. The optimal concentration of Co-dopant in CuO x nanocrystals renders the favorable surface properties for the electron transfer, the adsorption, and desorption of OER-relevant intermediates. Moreover, the small size of CuO x nanocrystals contributes to the large electrochemically active surface area, which enables the sufficient Co active sites to the electrolyte.