Developing highly efficient and durable electrocatalysts toward oxygen evolution reaction (OER) is an urgent demand to produce clean hydrogen energy. In this study, a series of medium-entropy metal sulfides (MEMS) of (NiFeCoX) 3 S 4 (where X = Mn, Cr, Zn) are synthesized by a facile onepot solvothermal strategy using molecular precursors. Benefiting from the multiple-metal synergistic effect and the low crystallinity, these MEMS show significantly enhanced electrocatalytic OER activity compared with the binary-metal (NiFe) 3 S 4 and ternary-metal (NiFeCo) 3 S 4 counterparts. Especially, (NiFeCoMn) 3 S 4 delivers a low overpotential of 289 mV at 10 mA cm −2 , a decent Tafel slope of 75.6 mV dec −1 and robust catalytic stability in alkaline medium, outperforming the costly IrO 2 benchmark electrocatalyst and the majority of the reported metal sulfide-based electrocatalysts until now. These MEMS with facile synthesis and excellent electrocatalytic performance bring a great opportunity to design desirable electrocatalysts for practical application.
Constructing nitrogen (N 2 ) adsorption and activation sites on semiconductors is the key to achieving efficient N 2 photofixation. Herein, Mn-W dual-metal sites on WO 3 are designed toward efficient N 2 photoreduction via controlled Mn doping. Impressively, the optimal 2.3% Mn-doped WO 3 (Mn-WO 3 ) exhibits a remarkable ammonia (NH 3 ) production rate of 425 µmol g cat.−1 h −1 , representing the best catalytic performance among the ever-reported tungsten oxide-based photocatalysts for N 2 fixation. Quasi in situ synchrotron radiation X-ray spectroscopy directly identifies that the Mn-W dual-metal sites can enhance the polarization of the adsorbed N 2 , which is beneficial to the N 2 activation. Further theoretical calculations reveal that the increased polarization is originated from the electron back-donation into the antibonding orbitals of the adsorbed N 2 , hence lowering the reaction energy barrier toward the N 2 photofixation. The concept of dual sites construction for inert molecule activation offers a powerful platform toward rational design of highly efficient catalysts for nitrogen fixation and beyond.
Single-atom
photocatalysts exhibit great potential for converting
solar energy into value-added chemicals or fuels, but the insufficient
efficiency of charge transfer from light-absorbed units to single-atom
catalytic sites limits the overall photocatalytic performance. Herein,
we developed an amorphization strategy of ferric oxide support to
accelerate the enrichment of photogenerated electrons to single-atom
Ru for enhanced nitrogen photofixation. The ammonia yield rate of
Ru single atoms distributed on amorphous ferric oxide nanosheets (Ru1/2DAF) in pure water reached 213 μmol·gcat.
–1·h–1, even four times
higher than that of the crystalline counterpart. Mechanistic studies
indicated that the amorphous structure could efficiently modulate
the electronic density of states to reduce the electron-transfer energy
barrier and guide electrons from amorphous support to Ru 4d orbitals
via d(Ru)–d(Fe) coupling. This work provides fresh insights
on the design of single-atom photocatalysts and emphasizes the importance
of the charge transfer behavior in tuning the catalytic activity.
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