Amorphous Cobalt‐Rich Trimetallic Boride‐Based Electrocatalyst for Efficient Water Oxidation

ABSTRACT Electrochemical splitting of water to generate clean hydrogen demands high‐performance electrocatalysts (ECs). But noble metal ECs are costly and scarce on Earth, restricting their widespread use. Transition metal borides (TMB) show outstanding performance in the oxygen evolution reaction (OER) and distinctive metalloid characteristics. Herein, trimetallic amorphous TMB (CNCB) nanosheets, synthesized via a low‐cost chemical reduction method, exhibit superior water oxidation activity over bi‐ and monometallic counterparts. Incorporating Ni (5%) and Cu (5%) into Co‐boride modulates the electronic structure of CNCB through a synergistic effect and reactive intermediate formation at active Co 3+ /Co 2+ , Ni 2+ , and Cu + sites, tuning exceptional OER kinetics. CNCB nanosheets exhibit a low overpotential ( η ) of 279 mV at 10 mA cm −2 , comparable to reported RuO 2 (301 mV) in 1 M KOH. CNCB has a small Tafel slope of 58 mV dec −1 and achieves an impressive current density of 282 mA cm −2 at 1.77 V vs. RHE. It demonstrated a high electrochemical surface area (ECSA) of 419 m 2 g −1 , supported by a double‐layer capacitance of 4.93 mF. Chronoamperometry (CA) and 5000‐cycle durability tests demonstrate excellent stability in alkaline media. These findings highlight CNCB as a promising OER candidate, offering a viable alternative to carbon‐free, non‐noble metal‐based ECs.