Valence-engineered MoNi4/MoOx@NF as a Bi-functional electrocatalyst compelling for urea-assisted water splitting reaction

Heterostructured Ni/NiO Nanoparticles on 1D Porous MoOx for Hydrolysis of Ammonia Borane

“…These results make it clear that the reduction reaction (NiO → Ni) becomes faster from 5H to 50H and almost reaches a balance under 50H and 100H, which is consistent with the analysis result of XRD by Rietveld refinements in Figure . As for Mo 3d spectra, the peaks detected at 229.5/232.7, 230.5/233.7, and 232.4/235.6 eV are attributed to Mo 4+ , Mo 5+ , and Mo 6+ , and the peaks observed at 228.5/231.7 eV are assigned to Mo 0 species, respectively . The H 2 /Ar volume ratio can determine the speed of the reaction (Mo 6+ → Mo 5+ → Mo 4+ ); this is why the fast decrease of Mo 6+ , the rapid increase of Mo 5+ , and the slow increase of Mo 4+ are observed from 5H to 20H.…”

MoS2 Nanosheets on MoNi4/MoO2 Nanorods for Hydrogen Evolution

“…Figure a shows the comparative Mo 3d XPS peak from MoNi 4 /MoO 2 and MoS 2 :MoNi 4 /MoO 2 (top) samples. Deconvolution of the Mo 3d peak from the MoNi 4 /MoO 2 sample delineates that individual peaks at 227.85, 229.39, 230.35, and 232.43 eV emerge due to different valance states of Mo 0 , Mo 4+ , Mo 5+ , and Mo 6+ , respectively. , Similarly, in hybrid MoS 2 :MoNi 4 /MoO 2 samples, the characteristic Mo 3d peak appeared at 229.52 eV, indicating the Mo 4+ oxidation state, and two corresponding peaks appeared at 232.67 and 235.93 eV, representing the Mo 6+ oxidation state. Also, a Mo 0 peak is obtained along with the S 2s peak at their respective positions of 227.32 and 226.64 eV. ,, Additionally, Figure b demonstrates the comparative XPS peak of Ni 2p both in MoNi 4 /MoO 2 and hybrid MoS 2 :MoNi 4 /MoO 2 .…”

“…For the MoNi 4 /MoO 2 sample, the peak at 852.62 eV (Figure b) corresponds to Ni 0 , while other peaks at 855.98 and 873.62 eV are attributed to the Ni 2+ oxidation state. ,, For the MoS 2 :MoNi 4 /MoO 2 hybrid material (Figure b), the characteristic peak positions of Ni 2p were found at 850.86 and 854.61 eV, which are attributed to the oxidation states of Ni 0 and Ni 2+ , respectively. Figure c shows the O 1s spectrum of MoNi 4 /MoO 2 at 530.49 eV, which is the characteristic of Mo–O species in MoO 2 , while the other peak at 532.98 eV is attributed to the H–O bond of surface absorption species at oxygen vacancies. , Furthermore, Figure d shows that the characteristic S 2p peak appeared only in the hybrid MoS 2 :MoNi 4 /MoO 2 and the respective peak positions at 162.35 and 163.53 eV are associated with the 2p 3/2 and 2p 1/2 spin–orbit doublets, respectively, indicating the S 2– oxidation state of sulfur from MoS 2 . , From the above XPS analysis, it is evident that the Mo 0 and Mo 4+ oxidation states refer to the successful formation of MoNi 4 and MoO 2 , respectively, in a solid solution where the intermetallic MoNi 4 gets phase-separated in the MoO 2 matrix for both the samples of MoNi 4 /MoO 2 and MoS 2 :MoNi 4 /MoO 2 . The presence of the Ni 0 oxidation state implies the formation of MoNi 4 in both the samples, while the appearance of Mo–O in the O 1s peak justifies the formation of MoO 2 in the composite nanorod.…”

“…A few XRD peaks were observed at 26.22, 36.72, 49.98, 53.17, and 63.42° corresponding to the (110), (112̅), (221̅), (121), and (223̅) crystal planes of metallic MoO 2 (JCPDS No. 98-001-7724). ,, The XRD pattern of the MoS 2 :MoNi 4 /MoO 2 nanohybrid sample shows the characteristic peaks of both 2H-MoS 2 and MoNi 4 /MoO 2 simultaneously, as depicted in Figure (black curve), indicating the growth of 2H-MoS 2 on the surface of MoNi 4 /MoO 2 nanorods. It should be mentioned here that there is no other impurity peaks are found in the XRD data of the hybrid material, which further implies that the successful formation of the hybrid material occurred with 2H-MoS 2 flakes on MoNi 4 /MoO 2 nanorods.…”

“…MoO 2 sample delineates that individual peaks at 227.85, 229.39, 230.35, and 232.43 eV emerge due to different valance states of Mo 0 , Mo 4+ , Mo5+ , and Mo 6+ , respectively 49,50. Similarly, in hybrid MoS 2 :MoNi 4 /MoO 2 samples, the characteristic Mo 3d peak appeared at 229.52 eV, indicating the Mo 4+ oxidation state, and two corresponding peaks appeared at 232.67 and 235.93 eV, representing the Mo 6+ oxidation state.…”