Single-atom electrocatalysts (SAEs) can realize the target of low-cost by maximum atomic efficiency. However, they usually suffer performance decay due to high energy states, especially in a harsh acidic water splitting environment. Here, we conceive and realize a double protecting strategy that ensures robust acidic water splitting on Ir SAEs by dispersing Ir atoms in/onto Fe nanoparticles and embedding IrFe nanoparticles into nitrogen-doped carbon nanotubes (Ir-SA@Fe@NCNT). When Ir-SA@Fe@NCNT acts as a bifunctional electrocatalyst at ultralow Ir loading of 1.14 μg cm −2 , the required overpotentials to deliver 10 mA cm −2 are 250 and 26 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 0.5 M H 2 SO 4 electrolyte corresponding to 1370-and 61-fold better mass activities than benchmark IrO 2 and Pt/C at an overpotential of 270 mV, respectively, resulting in only 1.51 V to drive overall water splitting. Moreover, remarkable stability is also observed compared to Pt/ C-IrO 2 .

A palladium phosphide electrocatalyst supported on carbon black (PdP2@CB) shows efficient water splitting in both alkaline and neutral electrolytes. Significantly lower overpotentials are required for PdP2@CB (27.5 mV in 0.5 m H2SO4; 35.4 mV in 1 m KOH; 84.6 mV in 1 m PBS) to achieve a HER electrocatalytic current density of 10 mA cm−2 compared to commercial Pt/CB (30.1 mV in 0.5 m H2SO4; 46.6 mV in 1 m KOH; 122.7 mV in 1 m PBS). Moreover, no loss in HER activity is detectable after 5000 potential sweeps. Only 270 mV and 277 mV overpotentials are required to reach a current density of 10 mA cm−2 for PdP2@CB to catalyze OER in 1 m KOH and 1 m PBS electrolytes, which is better OER activity than the benchmark IrO2 electrocatalyst (301 mV and 313 mV to drive a current density of 10 mA cm−2). 1.59 V and 1.72 V are needed for PdP2@CB to achieve stable water splitting catalytic current density of 10 mA cm−2 in 1 m PBS and 50 mA cm−2 in 1 m KOH for 10 h, respectively.

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Two-dimensional Mo/Mo 2 C heteronanosheets (Mo/ Mo 2 C-HNS) were successfully prepared via a NaCl template-assisted synthesis route followed by a controllable simultaneous reduction and carbonization of MoO 3 nanosheets for efficient hydrogen evolution reaction (HER) catalysis under both acidic and alkaline conditions. The Mo species in the atomically thin Mo/Mo 2 C-HNS not only guarantees the rapid transport of electrons but also optimizes the electronic configuration of β-Mo 2 C. Besides, the abundant Mo/β-Mo 2 C heterointerfaces in nanodimension afford large numbers of additional heterogeneous catalytic sites. HER electrocatalytic performance with overpotential of merely 89 mV to drive a current density of 10 mA/cm 2 in 0.5 M H 2 SO 4 is therefore achieved. Strikingly, stable chronoamperometric electrolysis for 20 h and also an impressive cycling stability with negligible overpotential decay over 4000 sweeps demonstrate its considerable durability in an acidic environment. These findings highlight the promising potential of Mo/Mo 2 C-HNS catalyst as an efficient and stable noble metal-free electrocatalyst toward the HER.

The ultra-stable highly efficient HER over a wide pH range on defect-rich MoN nanosheets synthesized using a modified salt-template process.

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We report a polysiloxane based single-ion conducting polymer electrolyte (SIPE) synthesized via hydrosilylation technique. Styrenesulfonyl (phenylsulfonyl) imide groups were grafted on the highly flexible polysiloxane chains followed by lithiation. The highly delocalized anionic charges in the grafted moiety give rise to weak association with lithium ions in the polymer matrix, resulting in lithium ion transference number close to unity (0.89) and remarkably high ionic conductivity (7.2 ×10 -4 Scm -1 ) at room temperature. The high flexibility arising from polysiloxane enables the glass transition temperature (T g ) to be below room temperature. The electrolyte membrane displays high thermal stability and a strong mechanical strength. A coin cell assembled with the membrane comprised of the electrolyte and poly(vinylidene-fluoride-cohexafluoropropene) (PVDF-HFP) performs remarkably well over a wide range of temperature with high charge-discharge rates.12 rule in a three step cyclic process.[36] Following the same mechanism, here, the vinylic part of SPSIK was attached to the polysiloxane chains upon addition of a Si-H bond.The grafting of SPSIK on PMHS chains followed by exchange of K + ions by Li + ions was clearly proven to be successful by FTIR and NMR spectra. As can be seen in the FTIR spectra of PMHS and SG (Fig. 1), the peak at 2167 cm -1 in PMHS, corresponding to Si-H bond, is disappeared in SG, which confirms the grafting of SPSIK. In addition, the peak at 1627 cm -1 in SPSIK, corresponding to the vinylic group, is also disappeared in SG, confirming the grafting, which consumes the vinylic group. Furthermore, the signature signal of Si-H, appears at 4.68 ppm ( 1 H NMR) in PMHS, and the three peaks in the range of 6.78 to 5.31 ppm ( 1 H NMR) in SPSIK corresponding to 3 vinylic protons, are disappeared in SG, validating the grafting of SP on the PMHS chains. [43,46]. Finally, the overall synthesis of SG electrolyte was confirmed by the coherence between the expected and the found values for all the elements, except for Si, in the elemental analysis. The deviation observed for Si is mainly attributed to the incomplete digestion of Si during the analysis, which was also noticed during the elemental analysis of commercial products of Si such as PMHS and poly(methylphenylsiloxane)(PMPS) ( Table S1 in Supporting Information). The GPC analysis of SG in the tetrahydrofuran (THF) mobile phase depicts the number average molecular weight (Mn) of 84,238, weight average molecular weight (Mw) of 150,230, and poly dispersity index (PDI) of 1.78 based on the polystyrene standard.