The development of high-performance, low-cost, and long-lasting electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is urgently needed for effective electrochemical water splitting. In the present study, an engineering process was employed to prepare “Lewis base-hungry” amorphous–crystalline nickel borate–nickel sulfide (Ni3(BO3)2–Ni3S2) heterostructures, which exhibited unprecedentedly high electrocatalytic activity toward both OER and HER in alkaline media. The optimal Ni3(BO3)2–Ni3S2/nickel foam (Ni3(BO3)2–Ni3S2/NF) electrode displayed an ultralow overpotential of only −92 and +217 mV to reach the current density of 10 mA cm–2 for HER and OER, respectively. When the Ni3(BO3)2–Ni3S2/NF electrode was used as both the anode and cathode for overall water splitting, a low cell voltage of 1.49 V was needed to achieve the current density of 10 mA cm–2, which was superior to the performance of most noble metal-free electrocatalysts. Results from density functional theory calculations showed that the Lewis base-hungry sites in the heterostructures effectively enhanced the chemisorption of hydrogen and oxygen intermediates, a critical step in HER and OER electrocatalysis. Results from this study highlight the significance of rational design and engineering of heterostructured materials for the development of high-efficiency electrocatalysts.

No abstract

NiFe layered double hydroxides (LDHs) have been denoted as benchmark non‐noble‐metal electrocatalysts for the oxygen evolution reaction (OER). However, for laminates of NiFe LDHs, the edge sites are active, but the basal plane is inert, leading to underutilization as catalysts for the OER. Herein, for the first time, light and electron‐deficient Li ions are intercalated into the basal plane of NiFe LDHs. The results of theoretical calculations and experiments both showed that electrons would be transferred from near Ni2+ to the surroundings of Li+, resulting in electron‐deficient properties of the Ni sites, which would function as “electron‐hungry” sites, to enhance surface adsorption of electron‐rich oxygen‐containing groups, which would enhance the effective activity for the OER. As demonstrated by the catalytic performance, the Li−NiFe LDH electrodes showed an ultralow overpotential of only 298 mV at 50 mA cm−2, which was lower than that of 347 mV for initial NiFe LDHs and lower than that of 373 mV for RuO2. Reasonable intercalation adjustment effectively activates laminated Ni2+ sites and constructs the electron‐deficient structure to enhance its electrocatalytic activity, which sheds light on the functional treatment of catalytic materials.

Highly efficient and low-cost oxygen reduction reaction electrocatalysts play key roles in the development of advanced energy conversion and storage devices, such as fuel cells and metal–air batteries. Herein, a facile strategy of synthesizing cobalt single atoms anchored on an ultrathin N-doped carbon nanosheet electrocatalyst (marked as CoSAs/N-CNS) via an in situ g-C3N4 template strategy was reported. Impressively, benefiting from highly active Co–Nx sites and highly porous and ultrathin nanosheet morphology which has rich edges and more three-phase boundaries, the as-synthesized CoSAs/N-CNS exhibits markedly enhanced ORR activities under alkaline conditions with half-wave potential (E 1/2) as high as 0.91 V vs RHE, as well as durability of ∼67 h. Furthermore, compared with Pt/C, the CoSAs/N-CNS-based Zn–air battery presents outstanding discharge–charge performance, larger power density of 157.7 mW cm–2, and robust durability with a slight decay after 150 h (900 cycles). The experimental and theoretical results fully show the advantages of CoSAs/N-CNS, which also provides a new insight for the design and development of high-performance atomically dispersed metal active site electrocatalysts toward ORR.

No abstract