Revealing the Synergy of Cation and Anion Vacancies on Improving Overall Water Splitting Kinetics

Abstract

The exact understanding for each promotional role of cation and anion vacancies in bifunctional water splitting activity will assist in the development of an efficient activation strategy of inert catalysts. Herein, systematic first-principles computations demonstrate that the synergy of anion-oxygen and cation-manganese vacancies (V O and V Mn ) in manganese dioxide (MnO 2 ) nanosheets results in abnormal local lattice distortion and electronic modulation. Such alterations enrich the accessible active centers, increase conductivity, enhance the water dissociation step, and favor intermediate adsorption-desorption, consequently promoting HER and OER kinetics. As proof of concept, robust electrocatalysts, MnO 2 ultrathin nanosheets doped with dual vacancies (DV-MnO 2 ) are obtained via a maturely chemical strategy. Detailed characterizations confirm the cation vacancies-V Mn contribute to enhanced conductivity and anion vacancies-V O enrich the active centers with optimized local electronic configurations, consistent with the simulative predictions. As expected, DV-MnO 2 exhibits exceptional bifunctionality with the strong assistance of synergetic dual vacancies which act as abundant "hot spots" for active multiple intermediates. Leading to a lower cell voltage (1.55 V) in alkali electrolyte is required to reach 10 mA cm −2 for the overall water splitting system. These atomic-level insights on synergetic DV can favor the development of activating strategy from inert electrocatalysts.

Unraveling the Synergy of Chemical Hydroxylation and the Physical Heterointerface upon Improving the Hydrogen Evolution Kinetics

“…Meanwhile, unassisted photocurrents during the 1600 s highlight the continuity and steadiness of this electrolyzer (Figures S31d−S31f, Supporting Movie). 38,39 These results undoubtedly demonstrate great potential for clean energy conversion from seawater and even wastewater. 40−42 Mechanistic Investigations.…”

Fe2O3/NiO Interface for the Electrochemical Oxygen Evolution in Seawater and Domestic Sewage

“…To explore the possibility in practical applications, a twoelectrode electrolyzer was assembled by coupling FNE300 with an efficient HER catalyst NiMo 4 /MoO 2 . 41 As presented in Figure 6a,b, the FNE300||NiMo 4 /MoO 2 electrolyzer can V), 22 CoMoOS-100/NF||Pt/C/NF (η 10 = 1.58 V), 19 Ru-MnFeP/NF||Ru-MnFeP/NF (η 10 = 1.47 V, η 100 ≈ 1.62 V), 21 and DV-MnO 2 ||DV-MnO 2 (η 10 = 1.55 V), 53 and comparable to the excellent electrolyzer NiFe-LDH/Ni f ||NiP 2 -FeP 2 /Cu NW/ Cu f (η 10 = 1.42 V). 23 Remarkably, the FNE300||NiMo 4 /MoO 2 electrolyzer presents promising activity in alkaline simulated and natural seawater.…”

Enhanced CO capture properties of Li2MnO3via inducing layered to spinel transition by cation doping with Fe, Co, Ni and Cu

“…14,44 Hence, these features suggest that the addition of the TM induces the layered Li 2 MnO 3 to spinel transition by the Mn 3+ formation and the corresponding anionic vacancy formation. 35,45…”

“…34 Moreover, both features are also associated with an increase of the anionic vacancy amount, as was expected for the Mn 4+ substitution with these cations. 35,36 All these Raman spectra (Fe-, Co-and Ni-Li 2 MnO 3 solid solutions) depicted a I A g /B g ratio increase and the presence of a signal at ∼656 cm −1 , this signal was not observed in the pristine Li 2 MnO 3 sample. In previous studies, it was shown that these features correspond to the transition from layered Li 2 MnO 3 to LiMn 2 O 4 and Li 4 Mn 5 O 12 (Li 1+x Mn 2−x O 4 , 0 < x < 0.33) spinel-like structures, respectively, confirming the analysis described in the previous XRD results.…”

“…14,44 Hence, these features suggest that the addition of the TM induces the layered Li 2 MnO 3 to spinel transition by the Mn 3+ formation and the corresponding anionic vacancy formation. 35,45 In the Fe-Li 2 MnO 3 solid solution case, the g-factor shift to a higher value suggests a ferromagnetic (FM) interaction due to Fe 3+ ions (L = 3, S = 1/2). Moreover, the Fe-Li 2 MnO 3 spectrum exhibits the contribution of a Dysonian and a Lorentzian line.…”