Accelerated Water Dissociation Kinetics By Electron‐Enriched Cobalt Sites for Efficient Alkaline Hydrogen Evolution

Abstract

Sluggish water dissociation kinetics in theVolmer step on platinum-free electrocatalysts limits the development of hydrogen evolution from economical water-alkali electrolyser. Herein, an unusual nanosheets electrocatalyst of molybdenum-doped cobalt selenide with selenium vacancy encapsulated within N-doped carbon matrix (Mo-Co 0.85 Se VSe /NC) for efficient hydrogen evolution reaction (HER) is reported. Benefiting from the optimized electronic structure, this Mo-Co 0.85 Se VSe /NC nanosheet exhibits a high catalytic activity for alkaline HER, achieving the current densities of 10 and 200 mA cm −2 at low overpotentials of 151 and 275 mV, respectively. These results are among the highest catalytic activities in respect with all previously reported transition-metal-selenide based HER electrocatalysts. The combined in situ spectroscopic and theoretical studies reveal that the incorporation of Modopant and Se vacancies into Co 0.85 Se efficiently enhances electron transfer from Mo to Co atom through the bridging Se atom, leading to the formation of enriched electronic Co site to accelerate water dissociation, eventually facilitating the overall alkaline HER process. An integrated Zn-H 2 O battery with a Mo-Co 0.85 Se VSe /NC cathode is developed to further demonstrate the potential applications of the newly developed HER catalyst.

Hydrogen Spillover-Bridged Volmer/Tafel Processes Enabling Ampere-Level Current Density Alkaline Hydrogen Evolution Reaction under Low Overpotential

“…Figure S25 shows the LSV curves recorded from Ni 3 S 2 /Cr 2 S 3 @NF, Ni 3 S 2 @NF, and Cr 2 S 3 @NF in 1.0 M KOH aqueous electrolyte (red curves) and 1.0 M KOH D 2 O electrolyte (blue curves), and the corresponding KIE values. The KIE values were calculated by the current density ratios from H 2 O and D 2 O electrolytes ( J H 2 O/ J D 2 O) at the selected potentials. , In 1.0 M KOH aqueous electrolyte, to reach a set of the current densities of 50, 100, 150, and 200 mA cm –1 , different sets of potentials are required for Ni 3 S 2 /Cr 2 S 3 @NF (−0.15, −0.16, −0.17, and −0.18 V vs RHE), Ni 3 S 2 @NF (−0.2, −0.25, −0.3, and −0.34V vs RHE), and Cr 2 S 3 @NF (−0.33, −0.37, −0.38, and −0.4 V vs RHE). Under the corresponding potentials, the measured current densities from the 1.0 M KOH D 2 O electrolyte are 36.2, 68.9, 98.0, and 124.2 mA cm –2 for Ni 3 S 2 /Cr 2 S 3 @NF; 21.9, 43.1, 66.0, and 88.5 mA cm –2 for Ni 3 S 2 @NF; and 14.9, 22.8, 33.6, and 42.8 mA cm –2 for Cr 2 S 3 @NF.…”

Modulating the Electronic Structure on Cobalt Sites by Compatible Heterojunction Fabrication for Greatly Improved Overall Water/Seawater Electrolysis

“…This result agreed well with the theoretical calculation model (Figure S2). 32 Figure 4a shows the XRD patterns of CoSe/MoSe 2 , CoSe, and MoSe 2 , which match that of the standard hexagonal MoSe 2 (JCPDS# 29-0914) and hexagonal CoSe (JCPDS# 89-2004), respectively. Notably, the peak intensity of MoSe 2 in CoSe/ MoSe 2 was weak, which may be attributed to its low crystallinity.…”

“…Actually, good interfacial compatibility is very important for improving the strength and density of interfacial bonding, which would significantly affect the catalytic activity and stability of electrocatalysts, but it is often neglected in the design of efficient electrocatalysts with an abundant heterointerface . Moreover, the overall water electrolysis performance of cobalt selenide was also affected by the limited spatial overlap between the valence electrons of the d state on cobalt (Co) atoms and the p state of reaction intermediates, leading to an undesirable reduction of the overpotential. − Also, optimizing the d-orbital electrons of Co atoms in the cobalt selenide catalyst could optimize the valence electrons of the d state and then modulate the d-band center. Therefore, approaches to improve the interfacial compatibility of a cobalt selenide-based electrocatalyst and regulate the electronic structure of Co sites may further optimize the performance .…”

Metal-encapsulated carbon nanotube arrays for enhancing electrocatalytic nitrate reduction in wastewater: importance of lying-down to standing-up structure transition

“…Note that an obvious downshift in the Co 2p XPS spectrum was seen in Co@NCNT/CC compared with Co@NCL/CC and P-Co@NCNT (Fig. 1b), signifying the lower oxidation state of Co. 21,22 This is possibly attributed to the better protection from better-crystallized carbon shells for inner metal particles, which prevents the entry of oxygen from the atmosphere. The Raman spectra of all the obtained porous carbons are also presented in Fig.…”