Inductive effects in cobalt-doped nickel hydroxide electronic structure facilitating urea electrooxidation

Electrochemical oxidation of urea provides an approach to prevent excess urea emissions into the environment while generating value by capturing chemical energy from waste. Unfortunately, the source of high catalytic activity in state-of-the-art doped nickel catalysts for urea oxidation reaction (UOR) activity remains poorly understood, hindering the rational design of new catalyst materials. In particular, the exact role of cobalt as a dopant in Ni(OH) 2 to maximize the intrinsic activity towards UOR remains unclear. In this work, we demonstrate how tuning the Ni:Co ratio allows us to control the intrinsic activity and number of active surface sites, both of which contribute towards increasing UOR performance. We show how Ni 90 Co 10 (OH) 2 achieves the largest geometric current density due to the increase of available surface sites and that intrinsic activity towards UOR is maximized with Ni 20 Co 80 (OH) 2 . Through density functional theory calculations, we show that the introduction of Co alters the Ni 3d electronic state density distribution to lower the minimum energy required to oxidize Ni and influence potential surface adsorbate interactions. • Ni 1-x Co x (OH) 2 catalysts were synthesized by the epoxide sol-gel method. • The electrochemical UOR activity of Ni 1-x Co x (OH) 2 catalysts was investigated. • The number of redox-active sites and intrinsic UOR activity changes with [Co]. • The influence Co has on the electronic structure of Ni 1-x Co x (OH) 2 was determined. • Geometric current density in UOR was maximized for Ni 90 Co 10 (OH) 2 .