Crystallinity‐Modulated Electrocatalytic Activity of a Nickel(II) Borate Thin Layer on Ni₃B for Efficient Water Oxidation

Abstract

The exploration of new efficient OER electrocatalysts based on nonprecious metals and the understanding of the relationship between activity and structure of electrocatalysts are important to advance electrochemical water oxidation. Herein, we developed an efficient OER electrocatalyst with nickel boride (Ni B) nanoparticles as cores and nickel(II) borate (Ni-B ) as shells (Ni-B @NB) via a very simple and facile aqueous reaction. This electrocatalyst exhibited a small overpotential of 302 mV at 10 mA cm and Tafel slope of 52 mV dec . More interestingly, it was found that the OER activity of Ni-B @NB was closely dependent on the crystallinity of the Ni-B shells. The partially crystalline Ni-B catalyst exhibited much higher activity than the amorphous or crystalline analogues; this higher activity originated from the enhanced intrinsic activity of the catalytic sites. These findings open up opportunities to explore nickel(II) borates as a new class of efficient nonprecious metal OER electrocatalysts, and to improve the electrocatalyst performance by modulating their crystallinity.

Synthesis of a Highly Efficient Oxygen‐Evolution Electrocatalyst by Incorporation of Iron into Nanoscale Cobalt Borides

“…[7,8]). [11][12][13] Furthermore, electrocatalytic activities of other transition-metal borides like MoB, [14] MoB 2 , [15] and Ni 3 B [16,17] are currently under investigation. [11][12][13] Furthermore, electrocatalytic activities of other transition-metal borides like MoB, [14] MoB 2 , [15] and Ni 3 B [16,17] are currently under investigation.…”

Amorphous Cobalt Iron Borate Grown on Carbon Paper as a Precatalyst for Water Oxidation

“…The Fe 2p XPS spectrum of Co 0.75 Fe 0.25 BO/CP is displayed in Figure c, indicating the valence of Fe is +3 . Moreover, the B 1s spectrum of Co 0.75 Fe 0.25 BO/CP shows one clear peak at 192.8 eV (Figure S6 in the Supporting Information), which can be assigned to the B−O bonding in borate . To prove the interaction between metal Co and phenylboronic acid, we explored the O 1s spectra of Co 0.75 Fe 0.25 BO/CP (Figure d).…”

“…Two distinct peaks were detected, where the peak at the high binding energy of about 531.7 eV can be classified as the B−O bond in phenylboronic acid . The other one at about 530.0 eV can be attributed to the connection between the metal and oxygen . These observations prove that Co is linked to the oxygen in phenylboronic acid to form the amorphous CoFe borate, which can be verified by O 1s XPS.…”

“…Recently, reasonably designed TM‐Pi catalysts were also applied in the OER under alkaline conditions, including N‐doped nickel metaphosphate, cobalt pyrophosphate, NiFe phosphate, and core–shell structured Ni 12 P 5 /Ni 3 (PO 4 ) 2 hollow spheres . In addition, the amorphous and crystalline TM borides (TMB), as the analog of TM phosphide and/or TM sulfides, have also been considered as efficient OER catalysts in alkaline conditions . It is expected that TM‐Bi, as the analog of TMB and TM‐Pi, should possess excellent OER activity, because they are the same family of materials.…”

Phosphate‐Based Electrocatalysts for Water Splitting: Recent Progress

“…A lot of transition metal compounds, such as transition metal oxides, hydroxides, borides, carbides, nitrides, phosphides, sulfides, selenides and phosphates with small overpotential and outstanding stability for water electrolysis have been explored for decades. For a brief comparison, the electrocatalytic activity of previously reported Ni‐based oxides, hydroxide, sulfide, selenide, phosphide, nitride, borate and phosphate are shown in Figure . It can be seen from Figure that Ni‐based phosphate (Ni : Pi−Fe) exhibits smaller overpotential among nickel‐based electrocatalysts, suggesting more outstanding electrocatalytic ability.…”