Water splitting via an electrochemical process to generate hydrogen is an economic and green approach to resolve the looming energy and environmental crisis. The rational design of multicomponent materials with seamless interfaces having robust stability, facile scalability, and low-cost electrocatalysts is a grand challenge to produce hydrogen by water electrolysis. Herein, we report a superhydrophilic homogeneous bimetallic phosphide of Ni2P–CuP2 on Ni-foam-graphene-carbon nanotubes (CNTs) heterostructure using facile electrochemical metallization followed by phosphorization without any intervention of metal-oxides/hydroxides. This bimetallic phosphide shows ultralow overpotentials of 12 (HER, hydrogen evolution reaction) and 140 mV (OER, oxygen evolution reaction) at current densities of 10 and 20 mA/cm2 in acidic and alkaline mediums, respectively. The excellent stability lasts for at least for 10 days at a high current density of 500 mA/cm2 without much deviation, inferring the practical utilization of the catalyst toward green fuel production. Undoubtedly, the catalyst is capable enough for overall water splitting at a very low cell voltage of 1.45 V @10 mA/cm2 with an impressive stability of at least 40 h, showing a minimum loss of potential. Theoretical study has been performed to understand the reaction kinetics and d-band shifting among metal atoms in the heterostructure (Ni2P–CuP2) that favor the HER and OER activities, respectively. In addition, the catalyst demonstrates an alternate transformation of solar energy to green H2 production using a standard silicon solar cell. This work unveils a smart design and synthesizes a highly stable electrocatalyst against an attractive paradigm of commercial water electrolysis for renewable electrochemical energy conversion.

We report a facile design and synthesis of magnetic iron oxide (IO) incorporated chitosan-graphene oxide (CSGO) hydrogel nanocomposites (CSGOIO) by employing in situ mineralization of iron ions in a hydrogel matrix. The mechanism of their formation was investigated by various physical methods, viz., FTIR, XRD, VSM, TGA, SEM, TEM, and BET. This approach was shown to have a direct impact on the morphological features and the structural order of the nanocomposites. The potential of the prepared nanocomposites for effective removal of a cationic dye, methylene blue (MB), from aqueous solution was investigated by performing a series of batch adsorption experiments, in line with the effect of adsorbent dosage, initial dye concentration, contact time, pH, ionic strength, and temperature. The adsorption was fairly influenced by the pH and ionic strength of the medium, indicating an electrostatic interaction between the adsorbent and MB molecules. The kinetics of adsorption followed a pseudo-second-order model, and equilibrium capacity was described by the Freundlich adsorption model. Interestingly, the nanocomposites exhibited a fast removal performance with a rate constant of 0.06 g mg–1 min–1. The hydrogel nanocomposites were found to possess an excellent adsorptive property after four successive cycles at different pH of the solution, thus providing a cost-effective material for dye removal applications. Therefore, this material, enabling dye removal in a wide variety of solution conditions, offered a promising platform for sustainable development of water purification technology.

Water splitting using renewable energy resources is an economic and green approach that is immensely enviable for the production of high-purity hydrogen fuel to resolve the currently alarming energy and environmental crisis. One of the effective routes to produce green fuel with the help of an integrated solar system is to develop a cost-effective, robust, and bifunctional electrocatalyst by complete water splitting. Herein, we report a superhydrophilic layered leaflike Sn4P3 on a graphene–carbon nanotube matrix which shows outstanding electrochemical performance in terms of low overpotential (hydrogen evolution reaction (HER), 62 mV@10 mA/cm2, and oxygen evolution reaction (OER), 169 mV@20 mA/cm2). The outstanding stability of HER at least for 15 days at a high applied current density of 400 mA/cm2 with a minimum loss of potential (1%) in acid medium infers its potential compatibility toward the industrial sector. Theoretical calculations indicate that the decoration of Sn4P3 on carbon nanotubes modulates the electronic structure by creating a higher density of state near Fermi energy. The catalyst also reveals an admirable overall water splitting performance by generating a low cell voltage of 1.482 V@10 mA/cm2 with a stability of at least 65 h without obvious degradation of potential in 1 M KOH. It exhibited unassisted solar energy-driven water splitting when coupled with a silicon solar cell by extracting a high stable photocurrent density of 8.89 mA/cm2 at least for 90 h with 100% retention that demonstrates a high solar-to-hydrogen conversion efficiency of ∼10.82%. The catalyst unveils a footprint for pure renewable fuel production toward carbon-free future green energy innovation.

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Supercapacitors (SCs) are considered promising energy storage systems because of their high power output and long-term cycling stability; however, they usually exhibit poor energy density. The hybrid supercapacitor (HSC) is an emerging concept in which two dissimilar electrodes with different charge storage mechanisms are paired to deliver high energy without sacrificing power output. This Perspective highlights the features of transition-metal phosphides (TMPs) as the positive electrode in HSCs. In particular, bimetallic nickel cobalt phosphide (NiCoP) with multiple redox sites, excellent electrochemical reversibility, and stability is discussed. We outline how the rational heterostructures, elemental variations, and nanocomposite morphologies tune the electrochemical properties of NiCoP as the positive electrode in HSCs. The Perspective further sheds light on NiCoP-based composites that help in improving the overall performance of HSCs in terms of energy density and cycling stability. The key scientific challenges and perspectives on building efficient and stable HSCs for future applications are discussed.

Vertically aligned carbon nanotubes (CNTs) have proven to be one of the best materials for use as an efficient field emitter. To further improve their efficiency as well as long-term use in practical devices, it is necessary to reduce the quantum resistance originating from the interface between electrode and emitters and the entanglement of the CNTs in a bundle texture. Thus, the incorporation of graphene at the bottom of CNT bundles via a seamless carbonaceous interface can easily solve this bottleneck. In this work we have demonstrated for the first time, growth and field emission properties of pure seamless graphene-CNT heterostructures and pure seamless graphene-vertically patterned oriented CNTs heterostructures (SGVCNTs) on Si/SiO2 substrates in contrast to the bare CNT mats and few-layer graphene structures without using any tedious post transfer processes. It was observed that seamless SGVCNTs show better field emission performance in terms of higher current density (236 mA cm−2), lowered turn-on field (0.45 V μm−1) and threshold field (1.931 V μm−1 @100 mA cm−2), and improved field enhancement factor (β ∼ 41 315) which is improved ∼4 fold when compared to a bare CNT mat. The significant improvement of the field emission performance of SGVCNTs is mainly attributed to the low resistive seamless C–C covalent carbonaceous interface, the higher number of emitter sites and patterned vertical orientation that leads to long-term stability of the field emitter with minimal loss up to 32 h. This finding could provide an important solution for carbonaceous material based field emitters for real phase device applications.

Electrochemical water splitting, which generates both hydrogen and oxygen, using highly efficient and low‐cost noble metal‐free (Pt, Ru, Ir etc.) electrocatalyst is an economical and green approach for the alternative energy source. Due to their conductivity, durability and long‐term stability, carbonaceous containing hybrid materials are used as promising electrodes for total water splitting. Herein, the design of metal‐phosphide (Cu3P) with graphitic carbon‐nitride (g‐C3N4) nanocomposite on 3D‐graphene is reported, a new model electrocatalyst that in turn, render superior electrocatalytic performance with long‐term stability. The excellent electrocatalytic performance is analyzed in terms of overpotentials of 67 mV and 255 mV at a current density of 10 mA/cm2 with a small Tafel slope of 45 and 40 mV/dec for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. The overall water splitting performance has been tested in 1 M KOH electrolyte, and the catalyst exhibits a very low cell voltage of 1.54 V to achieve a current density of 10 mA/cm2 with impressive stability of at least 35 hours with no loss of potential. This work sheds new insight into the design and synthesis of highly stable electrocatalyst that could be an apt choice for an attractive paradigm for commercial water electrolysis in renewable electrochemical energy conversion.

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