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

Abstract

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 , 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 at an overpotential of 550 mV.

Hierarchical Cobalt Borate/MXenes Hybrid with Extraordinary Electrocatalytic Performance in Oxygen Evolution Reaction

“…The strong interaction between Co‐B i and Ti 3 C 2 T x combined with spontaneous electron transfer, should accelerate the electrocatalytic OER redox process on the Co‐B i /Ti 3 C 2 T x hybrid. As observed in the B region, the peak at 192.1 eV can be assigned to the 1s core levels of B 3+ in borate species (Figure S9);, and the C 1s high‐resolution (Figure S10) is in agreement with previous reports …”

Water Oxidation Electrocatalysis with a Cobalt‐Borate‐Based Hybrid System under Neutral Conditions

“…[26,27] First-generation Co-Bi catalysts tookaback seat in the field mainly because of their relatively lower catalytic activities compared with well-knownC o-Pi systems. [36] These studies reveal that cobalt borate systemsa se lectrocatalysts could be ap romising directionint he field of water oxidation. Such catalysts have provent ob ee fficient and robustc atalysts, especiallyw hen hybridized with carbon-based supports such as graphene and carbon cloth.…”

“…[35] Furthermore, ab imetallic NiCo-Bic atalyst, which was directly convertedf rom NiCo-layered double hydroxide on nickel foam through oxidative polarization in borate electrolyte, performsa ta no verpotential of 430 mV for ac urrent density of 10 mA cm À2 . [36] These studies reveal that cobalt borate systemsa se lectrocatalysts could be ap romising directionint he field of water oxidation.…”

Hydrothermally Synthesized Cobalt Borophosphate as an Electrocatalyst for Water Oxidation in the pH Range from 7 to 14

“…The Tafel slopes of CoBP@FTO are 99, 77 and 57 mV dec −1 , which is the pH increases from 7 to 13.6, the Tafel slope gradually decreases (Figure d). These slopes are smaller than some amorphous borate catalyst that of Co−Bi NS/G Co−Bi (160 mV dec −1 , at pH 7), Ni−Co‐Bi/CC (142 mV dec −1 , at pH 9.2) and NiCo−Bi/NF (92 mV dec −1 , at pH 9.2) . 57 mV dec −1 of Tafel slope and 20 mA cm −2 of current density indicate that CoBP@FTO exhibits the best catalytic performance at pH 13.6.…”

“…These slopes are smaller than some amorphous borate catalyst that of CoÀ Bi NS/G CoÀ Bi (160 mV dec À 1 , at pH 7), [19] NiÀ Co-Bi/CC (142 mV dec À 1 , at pH 9.2) [28] and NiCoÀ Bi/ NF (92 mV dec À 1 , at pH 9.2). [29] 57 mV dec À 1 of Tafel slope and 20 mA cm À 2 of current density indicate that CoBP@FTO exhibits the best catalytic performance at pH 13.6. The onset potential of 1.46 V with low current densities and overpotentials of 384 mV extracted from CA were required to produce current densities of 1 mA cm À 2 at pH 13.6, while the same current density could be obtained at higher overpotential with some metal oxides (CoOx (η = 381 mV), [30] NiO x (η > 1000) [31] and FeOx (η = 445 mV)) [32] in basic solution (pH 14).…”