Controllable tuning of polymetallic Co-Ni-Ru-S-Se ultrathin nanosheets to boost electrocatalytic oxygen evolution

Abstract Replacing precious metals in oxygen evolution reaction (OER) catalysts has broad prospects to achieve a viable water splitting system. Since the electrocatalytic OER is a four-electron transfer reaction with a very sluggish kinetic process, there is great interest in the development of inexpensive, durable, and high-efficiency OER catalysts. Herein, trimetallic Co-Ni-Ru sulfoselenide and bimetallic sulfoselenide nanosheets were designed by regulating their composition and morphology for efficient and durable OER electrocatalysis. The sheet structure has a large specific surface area to promote contact between the catalyst and electrolyte. Compared with bimetallic Co-Ni, Co-Ru, Ni-Ru, Co-Cd, and Co-Au sulfoselenide nanosheets, trimetallic Co-Ni-Ru sulfoselenide nanosheets show superior OER performance. By modulating the composition ratio of metal atoms in the Co-Ni-Ru-S-Se nanosheets (1:1:0.5:1:1), the nanosheets showed a significant OER overpotential of η = 261 mV (1.491 V versus RHE) at 10 mA cm⁻², a Tafel slope of 52.2 mV dec^–1 and outstanding stability after 48 h of continuous testing. For comparison, Co-Ni, Co-Ru, Ni-Ru, Co-Cd, and Co-Au bimetallic sulfoselenide nanosheets (denoted as Co-Ni-S-Se, Co-Ru-S-Se, Ni-Ru-S-Se, Co-Au-S-Se, Co-Cd-S-Se) were also tested. Density functional theory (DFT) calculations showed that appropriately doping Ru and Ni simultaneously (Co-Ni-Ru-S-Se) can increase the density of the states at the Fermi level, resulting in excellent charge density and low intermediate adsorption energy. These findings present a practical route to design 2D polymetallic nanosheets to optimize catalytic OER performance.