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Heterogeneous electrocatalysis closely relies on the electronic structure of the catalytic materials. The ferroelectric‐to‐paraelectric phase transition of the materials also involves a change in the state of electrons that could impact the electrocatalytic activity, but such correlation remains unexplored. Here, we demonstrate experimentally and theoretically that the intrinsic electrocatalytic activity could be regulated as exampled by hydrogen evolution reaction catalysis over two‐dimensional ferroelectric CuInP2S6. The obvious discontinuity in the overpotential and apparent activation energy values for CuInP2S6 electrode are illustrated during the ferroelectric‐to‐paraelectric phase transition caused by copper displacement around Tc point (318 K), revealing the ferroelectro‐catalytic effect on thermodynamics and kinetics of electrocatalysis. When loading Pt single atom on the CuInP2S6, the paraelectric phase one showed an improved hydrogen evolution activity with smaller apparent activation energy over the ferroelectric phase counterpart. This is attributed to the copper hopping between two sulfur planes, which alternate between strong and weak H adsorption at the Pt sites to simultaneously promote H+ reactant adsorption and H2 product desorption. [ABSTRACT FROM AUTHOR]

For increasing scalability and reducing cost, transition metal dichalcogenides-based electrocatalysts presently have been proposed as substitutes for noble metals to generate hydrogen, but these alternatives usually suffer from inferior performance. Here, a Ravenala leaf-like W xC@WS2 heterostructure is grown via carbonizing WS2 nanotubes, whose outer walls being partially unzipped along with the W x C 'leaf-valves' attached to the inner tubes during the carbonization process. This heterostructure exhibits a catalytic activity for hydrogen evolution reaction with low overpotential of 146 mV at 10 mA cm−2 and Tafel slope of 61 mV per decade, outperforming the performance of WS2 nanotubes and W xC counterparts under the same condition. Density functional theory calculations are performed to unravel the underlying mechanism, revealing that the charge distribution between W xC and WS2 plays a key role for promoting H atom adsorption and desorption kinetics simultaneously. This work not only provides a potential low-cost alternative for hydrogen generation but should be taken as a guide to optimize the catalyst structure and composition. [ABSTRACT FROM AUTHOR]

To address the urgent need for clean and sustainable energy, the rapid development of hydrogen-based technologies has started to revolutionize the use of earth-abundant noble-metal-free catalysts for the hydrogen evolution reaction (HER). Like the active sites of hydrogenases, the cation sites of pyrite-type transition-metal dichalcogenides have been suggested to be active in the HER. Herein, we synthesized electrodes based on a Se-enriched NiSe2 nanosheet array and explored the relationship between the anion sites and the improved hydrogen evolution activity through theoretical and experimental studies. The free energy for atomic hydrogen adsorption is much lower on the Se sites (0.13 eV) than on the Ni sites (0.87 eV). Notably, this electrode benefits from remarkable kinetic properties, with a small overpotential of 117 mV at 10 mA cm−2, a low Tafel slope of 32 mV per decade, and excellent stability. Control experiments showed that the efficient conversion of H+ into H2 is due to the presence of an excess of selenium in the NiSe2 nanosheet surface. [ABSTRACT FROM AUTHOR]

As an effective alternative to noble platinum electrocatalyst, earth abundant and inexpensive layered transition metal dichalcogenides (TMDs) are investigated for the hydrogen evolution reaction (HER). Compared with binary TMDs, the tunably composed ternary TMDs have hitherto received relatively little attention. Here, few-layered ternary WS2(1− x)Se2 x nanoribbons (NRs) with metallic 1T phases, much more catalytically active in HER, are prepared for the first time. The favorable Δ GHo introduced by the tensile region on the surface, along with the presence of local lattice distortions of the WS2(1− x)Se2 x nanoribbons with metallic 1T phases, greatly promotes the HER process. These ternary NRs achieve the lowest overpotential of ≈0.17 V at 10 mA cm−2 and a Tafel slope of ≈68 mV dec−1 at a low catalyst loading (≈0.30 ± 0.02 mg cm−2). Notably, the long-term durability suggests the potential of practical applications in acid electrolytes. The results here suggest that the ternary WS2(1− x)Se2 x NRs with 1T phases are prominent alternatives to platinum-based HER electrocatalysts. [ABSTRACT FROM AUTHOR]

All carbon-based CG/M − CN rectangular nanotubes have been constructed by a facile molten salt thermal condensation of melamine and glucose. In the molten salt fluid, the glucose is carbonized into graphene-like (CG) nanosheets acting as an electron acceptor, and the melamine thermally condenses into carbon nitride (M − CN) rectangular nanotube acting as an electron donor. The 0.5 wt% CG/M − CN nanotubes display a photocatalytic H 2 evolution rate of 2345 μmol h−1 g−1, which is 1.52 times higher than that of M-CN. Moreover, without loading Pt co-catalyst, the 0.5 wt% CG/M − CN nanotubes show a 12.75 times higher photocatalytic H 2 evolution rate than that of M-CN. It is revealed that the graphene-like CG nanosheets not only can act as an electron acceptor boosting charge carrier separation, but also function as a HER cocatalyst for M-CN. Our work provides a new insight for the development of all carbon-based photocatalysts for energy-related applications. All carbon-based donor-acceptor (D-A) conjugated CG/M − CN rectangular tubular composites with HER cocatalyst free have been constructed through a facile one-step molten salt thermal condensation approach, which exhibits superior photocatalytic hydrogen evolution performance. [Display omitted] • The CG/M − CN composites are developed by a molten salt thermal condensation method. • CG acts as an electron acceptor and cocatalyst for M − CN to drive H 2 evolution. • The D-A conjugated system promotes fast charge carrier transfer in CG/M-CN. • The 0.5 wt% CG/M − CN without cocatalyst shows optimal photocatalytic performance. [ABSTRACT FROM AUTHOR]

Building carbon nitride (CN)-based core shell heterostructures is an effective strategy to enhance the photocatalytic performance and stability by optimize the interface area and protect the CN core, respectively. Moreover, by fabricating the porous structures in core shells can further optimize the light absorption, charge separation, and mass transfer. Herein, we have constructed porous C-PDA–CN–ms core-shell heterostructures through a facile green molten salt (ms) sculpture the polydopamine (PDA) derived carbon (C-PDA) shells with CN core. In which, the C-PDA-CN core-shells arise from in situ polymerization of dopamine (DA) on the surface of melamine to form PDA@melamine coatings followed by thermal polycondensation. The molten salts at high-temperature act as a green fluid immersing in and out of C-PDA-CN core-shells to further produce porous structures. The 1 wt% C-PDA–CN–ms with porous core-shell structures display photocatalytic H 2 evolution rate of 3830 μmol h−1 g−1, which is 20.8 times enhancement of 1 wt% C-PDA-CN core-shells, even 73.6 times higher than that of pristine CN. It reveals that the porous and core-shell heterostructures endow C-PDA–CN–ms enhanced light absorption, various charge transport channels for improved charge carrier separation and transfer, contributing to the superior photocatalytic H 2 evolution performance. Our work opens a new window for the green construction of porous core-shell heterostructures of CN-based photocatalysts. The porous C-PDA–CN–ms core-shells have been developed through a green molten salt sculpture approach, which promotes light absorption and charge carrier transfer for efficient photocatalytic H 2 evolution. [Display omitted] • Porous C-PDA/CN-ms core-shells are constructed by a molten salt sculpture approach. • Molten salt fluid sculpture C-PDA-CN core-shells to produce porous structures. • The porous C-PDA–CN–ms core-shells exhibit superior photocatalyticperformance. • The optimized photocatalytic H 2 evolution rate is 3830 μmol h−1 g−1, with a AQE of 39.6% at 420 nm. • The porous core-shells endow CN improved light absorption and charge separation. [ABSTRACT FROM AUTHOR]

• The C-TA/g-C 3 N 4 was obtained by supramolecular self-assembly and thermal condensation. • The TA with groups OH can link with melamine promoting the condensation of g-C 3 N 4. • The C-TA/g-C 3 N 4 with decreased interlayer distance effectively promote charge transfer. • The condensed C-TA/g-C 3 N 4 exhibit superior photocatalytic H2 evolution performance. Design of highly condensed g-C 3 N 4 is a prospective way to optimize the photoreactivity of g-C 3 N 4 as it possesses condensed structure with decreased interlayer spacing, which benefits both charge transfer and light harvesting. Herein, we report that novel condensed carbonized-tannic acid (C-TA)/g-C 3 N 4 composites have been acquired via a supramolecular self-assembly of TA and melamine into TA/melamine precursors followed by thermal condensation. The acquired condensed C-TA/g-C 3 N 4 composites present superior visible-light photocatalytic activity for H 2 evolution. The 1 wt% C-TA/g-C 3 N 4 composite shows 4.2 times enhancement of photocatalytic activity for H 2 evolution compared to pristine g-C 3 N 4. The TA with distinct adhesion properties and functional groups of OH, which is firmly linked with melamine, can confine the melamine inside to promote the condensation to gain more condensed g-C 3 N 4. The condensed C-TA/g-C 3 N 4 composites with decreased interlayer distance effectively promote charge transfer and photocatalytic H 2 evolution. [ABSTRACT FROM AUTHOR]

Highlights from the article: Due to the increasing environmental and energy issues, hydrogen, as a clean and non-carbon energy source, has received more and more attention in the past decades. 12 R. Gusmão, Z. Sofer, M. Pumera, Exfoliated layered manganese trichalcogenide phosphite (MnPX 3, X = S, Se) as electrocatalytic van der Waals materials for hydrogen evolution, Adv Funct Mater, 29, 2019, 1805975Gusmão R, Sofer Z, Pumera M, et al.