Fascinating Tin Effects on the Enhanced and Large-Current-Density Water Splitting Performance of Sn–Ni(OH)₂

Abstract

Ni­(OH)2-based materials are widely studied in oxygen evolution reaction (OER), but no related synthesis, electrocatalytic application, or theoretical analysis of Sn4+-doped Ni­(OH)2 has been reported. In this work, Sn–Ni­(OH)2 with a homogeneously distributed nanosheet array was synthesized through a one-step hydrothermal process. It displays a hugely enhanced catalytic activity compared to undoped Ni­(OH)2 throughout the OER and hydrogen evolution reaction (HER) processes. The overpotentials at 100 mA cm–2 of Sn–Ni­(OH)2 are 312 mV (OER) and 298 mV (HER), which are lower than the corresponding 396 and 427 mV of Ni­(OH)2, respectively. In addition, Sn–Ni­(OH)2 can deliver stable large current densities (at ≈500 and ≈1000 mA cm–2) for the long-term (>100 h) chronoamperometry testing. Moreover, Sn–Ni­(OH)2 illustrates catalytic activity comparable to that of a commercial Pt/C||RuO2 electrode pair during the overall water splitting course. Both experimental phenomena and relevant computed theoretical data confirm that the enhanced water splitting activity is mainly due to the introduced Sn4+ site, which acts as the active center activates the nearby Ni sites during the OER, while acting as the most active reaction site that participates in the HER. Although the doped Sn4+ has two different effects on OER and HER proceedings, water splitting performance of Sn–Ni­(OH)2 has been conspicuously improved.

V5+-Doped Potassium Ferrite as an Efficient Trifunctional Catalyst for Large-Current-Density Water Splitting and Long-Life Rechargeable Zn–Air Battery

“…As for Fe 2p (Figure b), the spectrum at BEs of 710.0 and 726.1 eV coincide with Fe 2p 3/2 and 2p 1/2 , respectively, demonstrating the existence of Fe 3+ . The slightly high BE shift (0.2 eV) of Fe 2p in V-KFO/NF is mainly attributed to the introduction of V . As displayed in Figure c, peaks at BEs of about 530.2 and 531.7 eV are attributed to O–Fe in KFO .…”

“…Apparently, the XRD data of V-KFO/NF basically coincide with that of the undoped KFO/NF. The diffraction peaks at 44.5, 51.8, and 76.3° belong to the NF substrate (PDF#04-0850) . Other peaks at 37.1, 43.2, and 62.7° are well indexed to the (111), (112), and (031) facets of KFO (PDF#39-1106), respectively …”

“…As for Fe 2p (Figure 2b), the spectrum at BEs of 710.0 and 726.1 eV coincide with Fe 2p 3/2 and 2p 1/2 , respectively, demonstrating the existence of Fe 3+ . 32 The slightly high BE shift (0.2 eV) of Fe 2p in V-KFO/NF is mainly attributed to the introduction of V. 31 As displayed in Figure 2c, peaks at BEs of about 530.2 and 531.7 eV are attributed to O−Fe in KFO. 30 The mildly low BE shift (0.15 eV) is also due to doped V. However, the spectrum at BE of 533.3 eV is due to the O−H in the H 2 O that comes from the absorbed water in the air.…”

“…The diffraction peaks at 44.5, 51.8, and 76.3°belong to the NF substrate (PDF#04-0850). 31 Other peaks at 37.1, 43.2, and 62.7°are well indexed to the (111), (112), and (031) facets of KFO (PDF#39-1106), respectively. 30 Scanning electron microscopy (SEM) images of V-KFO/NF are shown in Figure 1c,d.…”

Accelerating the Electrocatalytic Performance of NiFe–LDH via Sn Doping toward the Water Oxidation Reaction under Alkaline Condition

“…The Sn-doped Ni­(OH) 2 required overpotentials of only 312 and 298 mV to drive a current density of 100 mA/cm 2 under OER and HER conditions, respectively. The introduction of Sn 4+ ions activates the adjacent Ni sites for adsorbing the active OH – ions with optimized adsorption energy as compared with pristine materials . To the best of our knowledge, there is no report on Sn doping at NiFe–LDH for electrochemical water oxidation under alkaline conditions.…”