In-situ formed NiS/Ni coupled interface for efficient oxygen evolution and hydrogen evolution

Constructing Ni/NiS Heteronanoparticle-Embedded Metal–Organic Framework-Derived Nanosheets for Enhanced Water-Splitting Catalysis

“…As presented in Figure 2a, the annealed sample clearly displayed the Ni°peaks at 852.82 and 870.01 eV, while the other Ni 2p peaks were negatively shifted by 0.56 to 1 eV demonstrating the presence of a nickel high electron affinity in the annealed sample. 49,53 Interestingly, the sulfide sample (Ni-M@C-130) prepared using TAA followed by annealing at 350 °C displayed Ni°, Ni 2+ , S 2− , and sulfate ions on its surface. As depicted in Figure 2b, the Ni 2p XPS spectrum contains a small peak at 853.41 eV, which represents the presence of Ni°nanoparticles in the material, while the two strong peaks positioned at 856.82 and 874.60 eV suggest the existence of Ni 2+ ions corresponding to both NiS nanoparticles and leftover MOF.…”

“…As depicted in Figure 2b, the Ni 2p XPS spectrum contains a small peak at 853.41 eV, which represents the presence of Ni°nanoparticles in the material, while the two strong peaks positioned at 856.82 and 874.60 eV suggest the existence of Ni 2+ ions corresponding to both NiS nanoparticles and leftover MOF. 49 Moreover, the high-resolution S 2p XPS spectrum reveals the existence of two main peaks corresponding to metal sulfides (S 2− ) and the surface-oxidized sulfate (S− O) units. The characteristic metal−sulfur bond deconvoluted into three peaks located at 161.69 (S 2p 3/2 ), 162.80 (S 2p 1/2 ), and 164.16 (metal−S) eV, confirming the presence of Ni−S bonding of NiS nanoparticles, 54,55 while the peak appearing at 169.18 eV indicates the existence of sulfur with a higher oxidation state possibly due to the surface oxidation of the material upon areal exposure.…”

“…Also, the significantly better OER activity of partially sulfurized samples over the annealed nanosheets (Ni@Ni-M@C) without TAA treatment demonstrate the significance of Ni/ NiS synergy in enhancing the OER activity. 49 Moreover, the Ni-M@C-130 sample displayed much better OER activity over the commercial RuO 2 (269 mV at η 10 ), approving its significance as a water oxidation catalyst. The significantly better OER performance of Ni-M@C-130 over the other samples prepared at higher temperatures (Ni-M@C-150 and Ni-M@C-170), could be due to the combined advantages of both the MOF architecture and electrochemically active Ni and (α,β)-NiS heteronanoparticles.…”

“…19 In addition, the performance is much superior to the other metal sulfidebased electrocatalysts studied on glassy carbon electrodes. For example, the mulberry-like Ni/NiS nanoparticles (301 mV at η 10 ), 49 N-and S-codoped rGO-wrapped Ni/NiS nanoparticles [FCC-Ni-NiS/NS-rGo (254 mV at η 10 )], 61 in situ grown NiS microspheres on a Ni foam substrate [NiS/NF (335 mV at η 10 )], 62 N-doped heterostructural NiS/NiS 2 nanoparticles [N-NiS/NiS 2 (270 mV at η 10 )], 63 a series of NiS x nanocrystals synthesized from a polyol solution process [Ni 3 S 2 @graphite (295 mV at η 10 ); NiS@graphite (357 mV at η 10 ); NiS 2 @ graphite (375 mV at η 10 )], 64 porous hollow NiS microspheres [NiS (320 mV at η 10 )], 65 two-dimensional NiS/graphene heterostructure composites [NiS/G (300 mV at η 10 )], 66 nickel sulfide/nitrogen-doped mesoporous carbon [NiS x /NMC, where NiS x = Ni 3 S 4 and NiS combination (340−380 mV at η 10 depends on mesoporous carbon concentration)], 67 and many other metal sulfide-based water oxidation catalysts reported earlier (Table S1).…”

Simultaneous heterostructure engineering and Mn doping modulation of Ni2P nanosheet arrays for enhanced electrocatalytic water splitting

“…Ni 2+ /Ni 3+ molar ratio drops from 1.57 to 0.87 after the stability test (Fig. S22), confirming that Ni x S y and Ni 2 P are oxidized into nickel oxyhydroxides/hydroxides under anodic potentials [54,55]. Meanwhile, for Mn-doped Ni 2 O 3 /Ni 2 P, the Ni 2+ /Ni 3+ molar ratio increases from 0.86 to 1.71, while the OH − (blue line)/metal oxide (red line) molar ratio increases from 6.7 to 8.9 after the stability test (Fig.…”