The design of two-dimensional (2D) ultrathin nanosheets with favorable electronic and optic properties that can satisfy the essential requirements of photocatalytic water splitting remains a challenge. Anisotropic Janus 2D materials exhibit fascinating potential due to their excellent photocatalytic performance, yet the scarcity of such materials limits their wide application. Herein, an allotrope of GeS and SnS monolayers with a ε-phosphorene-like atomic arrangement (ε-GeS and ε-SnS monolayers) is predicted to be a promising electrocatalyst for photocatalytic water splitting by first-principles calculations, and the results attest to its good stabilities. Both Janus monolayers prove to be semiconducting with direct band gaps of 2.63 eV for ε-GeS and 2.41 eV for ε-SnS, straddling the redox potentials of water. HSE calculations reveal that both GeS and SnS allotropes display notable anisotropy along with high hole mobility (∼10 3 cm 2 V −1 s −1 ). Moreover, both monolayers present strong optical absorption in the visible-light excitation range (10 5 cm −1 ), thus ensuring efficient harvesting for solar energy. Particularly, spontaneous hydrogen (HER) and oxygen evolution (OER) half reactions can occur simultaneously, driven only by sunlight-induced carriers, which still work even under strain. More interestingly, after transition-metal atom (from Sc to Zn) decoration, Co/ε-GeS and Sc/ε-SnS are confirmed as the most efficient single-atom HER catalysts, capable of driving HER with low overpotentials of 0.02 and −0.05 V, respectively, even outperforming the commercial Pt catalyst (−0.09 V). Meanwhile, for OER, low-overpotential Ni/ε-SnS (0.42 V) proves to be better than the generally used IrO 2 catalyst (0.55 V).
Bi3+-related metal-to-metal
charge transfer (MMCT) transition
phosphors are expected to become a new class of solid-state luminescent
materials due to their unique broadband long-wavelength emission;
however, the main obstacle to their application is the thermal quenching
effect. In this study, one novel thermal quenching mechanism of Bi3+-MMCT transition luminescence is proposed by introducing
electron-transfer potential energy (ΔE
T). Y0.99V1–x
P
x
O4:0.01Bi3+ (YV1–x
P
x
O4:Bi3+) is used as the model; when the band gap
of the activator Bi3+ increases from 3.44 to 3.76 eV and
the band gap of the host YV1–x
P
x
O4 widens from 2.75 to 3.16 eV, the
electron-transfer potential energy (ΔE
T) decreases and the thermal quenching activation energy (ΔE) increases, which result in the relative emission intensity
increasing from 0.06 to 0.64 at 303–523 K. Guided by density
functional calculations, the thermal quenching mechanism of the Bi3+-MMCT state transition luminescence is revealed by the double-band-gap
modulation model of the activator ion and the matrix. This study improves
the thermal quenching theory of different types of Bi3+ transition luminescence and offers one neo-theory guidance for the
contriving and researching of high-quality luminescence materials.
Two-dimensional (2D) graphitic carbon nitride skeleton offer rich hollow sites for stably anchoring transition-metal (TM) atoms to promote single-atom catalysis, which is expected to overcome a great challenge of low...
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