Composition-tunable Co3-xFexSe4 as efficient electrocatalysts for the oxygen evolution reaction

In the oxygen evolution reaction (OER), the selection of highly active catalysts is fundamental to curtail overpotentials and to enhance the typically sluggish kinetics characteristic of the reaction. Cobalt selenide (Co3Se4), with its optimally configured electronic structure of cobalt ions, is consistently hailed as a prospective electrocatalyst for the OER, making it highly efficient in facilitating the reaction. Despite the persistent challenges of the exposure of catalytic active sites and the limited electronic conductivity, our study unveils a breakthrough solution. We introduce a highly efficient Fe-doped Co3Se4 electrocatalyst for the OER, addressing these long-standing issues, and it has desirable compositional flexibility, formed Co3-xFexSe4 (0 ≤ x ≤ 3) selenides, by introducing Fe doping, the electronic structure of Co3Se4 is effectively regulated, resulting in a remarkable reduction in the overpotential of the OER under alkaline conditions. Simultaneously, the introduction of Fe induces the formation of highly active Co–O sites, ultimately establishing a highly active and stable catalytic surface for oxygen evolution. Consequently, this leads to a significant improvement in the activity of the oxygen evolution reaction (OER). The synthesized Co2.5Fe0.5Se4 catalyst exhibits lower overpotential (η10 = 220 mV) and Tafel slope (41.2 mV dec−1), which is superior to the general commercial RuO2 benchmark. In addition, Co2.5Fe0.5Se4 also exhibits exceptional structural integrity and sustained operational longevity, with a durability of up to 280 h at 100 mA cmgeo−2. Impressively, the Pt/C∥Co2.5Fe0.5Se4 water electrolysis cell only requires a battery voltage of 1.67 V to provide a current density of 100 mA cmgeo−2 and has excellent long-term stability.