Amorphous Nickel‐Cobalt‐Borate Nanosheet Arrays for Efficient and Durable Water Oxidation Electrocatalysis under Near‐Neutral Conditions

Electrolytic hydrogen generation needs earth‐abundant oxygen evolution reaction electrocatalysts that perform efficiently at mild pH. Here, the development of amorphous nickel‐cobalt‐borate nanosheet arrays on macroporous nickel foam (NiCo‐Bi/NF) as a 3D catalyst electrode for high‐performance water oxidation in near‐neutral media is reported. To drive a current density of 10 mA cm−2, the resulting NiCo‐Bi/NF demands an overpotential of only 430 mV in 0.1 m potassium borate (K‐Bi, pH 9.2). Moreover, it also shows long‐term electrochemical durability with maintenance of catalytic activity for 20 h, achieving a high turnover frequency of 0.21 s−1 at an overpotential of 550 mV. NiCo‐Bi nanosheet arrays on nickel foam support behaves as 3D catalyst electrode for water oxidation at near‐neutral pH. This electrode achieves a catalytic current density of 10 mA cm−2 at an overpotential of 430 mV with strong electrochemical stability in 0.1 m K‐Bi.