Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel–carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm−2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis.

Efficient and durable electrocatalysts from earth-abundant elements play a vital role in the key renewable energy technologies including overall water splitting and hydrogen fuel cells. Here, generally used CoFe based layered double hydroxides (LDHs) were first delaminated and exfoliated in the DMF-ethanol solvent (CoFe LDH-F), with enhancement both in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The exfoliation process creates more coordinatively unsaturated metals and improves the intrinsic electronic conductivity, which is important in water electrolyzer reactions. In the basic solution, the CoFe LDH-F catalyst outperforms the commercial iridium dioxide (IrO) electrocatalyst in activity and stability for OER and approaches the performance of platinum (Pt) for HER. The bifunctional electrocatalysts can be further used for overall water splitting, with a current density of ∼10 mA/cm at the applied voltage of 1.63 V for long-term electrolysis test, rivalling the performance of Pt and IrO combination as benchmarks. Our findings demonstrate the promising catalytic activity of LDHs for scale-up alkaline water splitting.

The layer-structured MoS is a typical hydrogen evolution reaction (HER) electrocatalyst but it possesses poor activity for the oxygen evolution reaction (OER). In this work, a cobalt covalent doping approach capable of inducing HER and OER bifunctionality into MoS for efficient overall water splitting is reported. The results demonstrate that covalently doping cobalt into MoS can lead to dramatically enhanced HER activity while simultaneously inducing remarkable OER activity. The catalyst with optimal cobalt doping density can readily achieve HER and OER onset potentials of -0.02 and 1.45 V (vs reversible hydrogen electrode (RHE)) in 1.0 m KOH. Importantly, it can deliver high current densities of 10, 100, and 200 mA cm at low HER and OER overpotentials of 48, 132, 165 mV and 260, 350, 390 mV, respectively. The reported catalyst activation approach can be adapted for bifunctionalization of other transition metal dichalcogenides.

In this work, we developed a general two-step method to prepare molybdenum carbide (Mo2C) nanoparticles stabilized by a carbon layer on reduced graphene oxide (RGO) sheets. The Mo2C-RGO hybrid showed excellent performance, which is attributed to the intimate interactions between Mo2C and graphene as well as the outer protection of the carbon layer.

Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

Water-alkaline electrolysis holds a great promise for industry-scale hydrogen production but is hindered by the lack of enabling hydrogen evolution reaction electrocatalysts to operate at ampere-level current densities under low overpotentials. Here, we report the use of hydrogen spillover-bridged water dissociation/ hydrogen formation processes occurring at the synergistically hybridized Ni 3 S 2 /Cr 2 S 3 sites to incapacitate the inhibition effect of high-current-density-induced high hydrogen coverage at the water dissociation site and concurrently promote Volmer/Tafel processes. The mechanistic insights critically important to enable ampere-level current density operation are depicted from the experimental and theoretical studies. The Volmer process is drastically boosted by the strong H 2 O adsorption at Cr 5c sites of Cr 2 S 3 , the efficient H 2 O* dissociation via a heterolytic cleavage process (Cr 5c -H 2 O* + S 3c (#) → Cr 5c -OH* + S 3c -H # ) on the Cr 5c /S 3c sites in Cr 2 S 3 , and the rapid desorption of OH* from Cr 5c sites of Cr 2 S 3 via a new water-assisted desorption mechanism (Cr 5c -OH* + H 2 O(aq) → Cr 5c -H 2 O* + OH − (aq)), while the efficient Tafel process is achieved through hydrogen spillover to rapidly transfer H # from the synergistically located H-rich site (Cr 2 S 3 ) to the H-deficient site (Ni 3 S 2 ) with excellent hydrogen formation activity. As a result, the hybridized Ni 3 S 2 /Cr 2 S 3 electrocatalyst can readily achieve a current density of 3.5 A cm −2 under an overpotential of 251 ± 3 mV in 1.0 M KOH electrolyte. The concept exemplified in this work provides a useful means to address the shortfalls of amperelevel current-density-tolerant Hydrogen evolution reaction (HER) electrocatalysts.

Electrochemically etched α-Co(OH)2–Cl, due to the dechlorination-induced defective structures and in situ formation of CoOOH fragments, are highly active for OER.

tuning strategy [14,15] with improved moisture tolerance. On the other hand, we have first demonstrated a surface functionalization method of MAPbI 3 (MA = CH 3 NH 3 + ) film with tetra-alkyl ammonium molecules which could tremendously enhance the humid stability of the perovskite device even under very harsh condition (90% relative humidity). [16] Furthermore, a series of hydrophobic molecules, such as alkylphos phonic acid ω-ammonium chloride, [17] dodecyltrimethoxysilane (C 12 -silane), [18] polystyrene, [19,20] polymethyl methacrylate, [21] and phenylethylammonium iodide, [22] were developed to enhance the moisture tolerance of perovskites. In addition, encapsulation was another effective way to protect perovskites form degradation induced by ambient moisture. [23][24][25][26] However, it was found that the organic layers with insulated alkyl groups usually limit the carrier extraction and thus result in slight loss of PCEs in our experiments.To protect the perovskite devices with high efficiency, surface-functionalized molecules must combine excellent electrical conductivity and hydrophobic properties. Among various molecules, thiophene derivatives enable the electron-rich conjugated π system, which consist of four 2p orbital electrons from carbon atoms and two lone electron pairs from sulfur atom. [27] These thiophene-based derivatives or polythiophene derivatives are usually used as sufficient hole extraction materials, together with the advantage of their highest occupied molecular orbital (HOMO). [28] Moreover, unlike siloxanes and amines, thiophenes can be directly coordinated to the lead atom by the lone pair of electrons offered by the sulfur atom, which may be directly interacted with the valance band of perovskite. [29] Therefore, if we modify perovskite surface with such molecules, device with high efficiency and stability is expected.In this work, we reported a new strategy to fabricate moisturetolerant and high-performance PSCs by employing 3-alkylthiophene derivatives as the multifunctional surface layer. This class of molecules contains unique delocalized conjugated π systems and hydrophobic alkyl groups that can enhance the charge transfer at perovskite/2,2′-7,7′-tetrakis[N,N-di(4-methoxyphenyl) amino]-9,9′-spirobifluorene (Spiro-OMeTAD) interface and protect the inner perovskite. Planar heterojunction devices utilizing Although the efficiency of perovskite solar cells (PSCs) is close to crystalline silicon solar cells, the instability of perovskite, especially in humid condition, still hinders its commercialization. As an effective method to improve their stability, surface functionalization, by using hydrophobic molecules, has been extensively investigated, but usually accompanied with the loss of device efficiencies owing to their intrinsic electrical insulation. In this work, for the first time, it is demonstrated that 3-alkylthiophene-based hydrophobic molecules can be used as both water-resistant and interface-modified layers, which could simultaneously enhance both stability and perform...