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The application of electrochemical hydrogen evolution reaction (HER) for renewable energy conversion contributes to the ultimate goal of a zero-carbon emission society. Metal phosphides have been considered as promising HER catalysts in the alkaline environment, which, unfortunately, is still limited owing to the weak adsorption of H* and easy dissolution during operation. Herein, a bimetallic NiCoP-2/NF phosphide is constructed on nickel foam (NF), requiring rather low overpotentials of 150 mV and 169 mV to meet the current densities of 500 and 1000 mA cm−2, respectively, and able to operate stably for 100 h without detectable activity decay. The excellent HER performance is obtained thanks to the synergetic catalytic effect between Ni and Co, among which Ni is introduced to enhance the intrinsic activity and Co increases the electrochemically active area. Meanwhile, the protection of the externally generated amorphous phosphorus oxide layer improves the stability of NiCoP/NF. An electrolyser using NiCoP-2/NF as both cathode and anode catalysts in an alkaline solution can produce hydrogen with low electric consumption (overpotential of 270 mV at 500 mA cm−2). [ABSTRACT FROM AUTHOR]

Highlights: The [W–O] group with strong adsorption capacity is introduced into CoP to fabricate a bi-functional catalyst towards HER and HzOR. The cell voltage of HzOR coupled electrolyzer with 6W–O–CoP/NF as both anode and cathode catalysts is 1.634 V lower than that of the water splitting system at 100 mA cm−2. A proof-of-concept self-powered H2 production system is assembled to realize the H2 evolution rate of 3.53 mmol cm−2 h−1. Hydrazine oxidation reaction (HzOR) assisted hydrogen evolution reaction (HER) offers a feasible path for low power consumption to hydrogen production. Unfortunately however, the total electrooxidation of hydrazine in anode and the dissociation kinetics of water in cathode are critically depend on the interaction between the reaction intermediates and surface of catalysts, which are still challenging due to the totally different catalytic mechanisms. Herein, the [W–O] group with strong adsorption capacity is introduced into CoP nanoflakes to fabricate bifunctional catalyst, which possesses excellent catalytic performances towards both HER (185.60 mV at 1000 mA cm−2) and HzOR (78.99 mV at 10,00 mA cm−2) with the overall electrolyzer potential of 1.634 V lower than that of the water splitting system at 100 mA cm−2. The introduction of [W–O] groups, working as the adsorption sites for H2O dissociation and N2H4 dehydrogenation, leads to the formation of porous structure on CoP nanoflakes and regulates the electronic structure of Co through the linked O in [W–O] group as well, resultantly boosting the hydrogen production and HzOR. Moreover, a proof-of-concept direct hydrazine fuel cell-powered H2 production system has been assembled, realizing H2 evolution at a rate of 3.53 mmol cm−2 h−1 at room temperature without external electricity supply. [ABSTRACT FROM AUTHOR]

Enhancing the durability of catalysts is of critical significance to industrialize green hydrogen production. Herein, a novel active site in situ refreshing strategy is proposed and demonstrated to fabricate highly active and ultra‐durable hydrogen evolution reaction (HER) electro‐catalytic material by HER activation. Briefly, a composite catalytic material is synthesized, which features Ni(PO3)2 active sites being embedded inside the amorphous Mo compound matrix (named NiMoO‐P). The Mo compound matrix undergoes gradual dissolution during HER followed by a dynamic equilibrium between the dissolution and deposition of the amorphous matrix. This process promotes the continuous exposure of insoluble Ni(PO3)2 and Ni2P partially converted from Ni (PO3) 2 in situ on the surface during HER activation. Thus, activated catalyst exhibits excellent HER performance featuring an extremely high current density of 1500 mA cm−2 at a rather low overpotential of 340 mV, and more attractively, an ultra‐long durability for hydrogen evolution for at least 1000 h at an industrial‐applicable current density of 900 mA cm−2. The mechanisms for the especially high HER performance are attributed to the exposure and continuous refreshing of Ni(PO3)2 and the in situ formed Ni2P during the HER process based on the DFT calculations and quasi‐in situ Raman spectroscopic monitoring. [ABSTRACT FROM AUTHOR]

A novel Zn−Fe flow battery featuring an Fe3+ reduction reaction (Fe3+RR)‐coupled zinc oxidation, and an Fe2+ oxidation reaction (Fe2+OR)‐coupled hydrogen evolution reaction (HER) system as well, was established. This battery is capable of driving two Fe2+OR‐coupled HER systems in series based on the above Fe2+/Fe3+ cycling, for efficient self‐powered hydrogen evolution. Meanwhile, this Fe2+/Fe3+ cycling enables the preparation of a multifunctional catalyst, Pt‐3@SXNS (siloxene nanosheet), by the Fe2+OR‐promoted dispersion of Pt nanoparticles on SXNS; alternatively, this support could be obtained by Fe3+RR‐assisted exfoliation using Fe3+ from the anolyte of Fe2+OR‐coupled HER. The Pt‐3@SXNS catalyst exhibits excellent catalytic activities toward Fe3+RR in the Zn−Fe flow battery, HER, and Fe2+OR in the electrolyzer, which is attributed to the strong electronic interaction between Pt and Si. This work offers a new strategy for energy storage and low‐cost hydrogen production from acidic wastewater. [ABSTRACT FROM AUTHOR]

A novel Zn−Fe flow battery featuring an Fe3+ reduction reaction (Fe3+RR)‐coupled zinc oxidation, and an Fe2+ oxidation reaction (Fe2+OR)‐coupled hydrogen evolution reaction (HER) system as well, was established. This battery is capable of driving two Fe2+OR‐coupled HER systems in series based on the above Fe2+/Fe3+ cycling, for efficient self‐powered hydrogen evolution. Meanwhile, this Fe2+/Fe3+ cycling enables the preparation of a multifunctional catalyst, Pt‐3@SXNS (siloxene nanosheet), by the Fe2+OR‐promoted dispersion of Pt nanoparticles on SXNS; alternatively, this support could be obtained by Fe3+RR‐assisted exfoliation using Fe3+ from the anolyte of Fe2+OR‐coupled HER. The Pt‐3@SXNS catalyst exhibits excellent catalytic activities toward Fe3+RR in the Zn−Fe flow battery, HER, and Fe2+OR in the electrolyzer, which is attributed to the strong electronic interaction between Pt and Si. This work offers a new strategy for energy storage and low‐cost hydrogen production from acidic wastewater. [ABSTRACT FROM AUTHOR]

Siloxene features abundant functional groups and oxygen vacancies, which facilitates the ultrafine platinum nanoparticles loading for catalyzing hydrogen evolution reaction (HER). Herein, a siloxene-p-Pt-2 h composite has been fabricated with an ultralow platinum loading on siloxene (0.56 wt%), which shows greatly enhanced HER activity featuring an ultralow overpotential (η 10 = 23 mV). Attractively, the siloxene-p-Pt-2 h has been applied as a HER catalyst in a Zn-H 2 O fuel cell, demonstrating a high power density of 157 mW cm−2 in coupling with the cathode hydrogen evolution. Moreover, a coupled configuration between two Zn-H 2 O fuel cells in series and the cell-powered hydroxide electrolyzer achieves the efficient hydrogen co-productions co-catalyzed by the HER catalysts. The excellent HER performance is attributed to the hydrophilic character and the optimal Gibbs free energy via the strong interaction between the siloxene and platinum nanoparticles. This work provides a novel design of self-powered co-productions of hydrogen. Two dimensional siloxene containing abundant functional groups was demonstrated as an effective support to load ultralow platinum nanoparticles (0.56 wt%), which shows superior HER performance in both Zn-H 2 O cells and water electrolysis attributing to the excellent hydrophilia of siloxene and the faster carrier mobility as well as the suitable value of hydrogen Gibbs free energy (ΔG H*). [Display omitted] • A novel strategy to facilely synthesize siloxene-p-Pt catalysts is developed. • Siloxene-p-Pt exhibits excellent HER activity in water splitting and Zn-H 2 O cells. • Hydrogen co-evolutions from Zn-H 2 O cells-powered water splitting is constructed. • The strong electronic interaction and hydrophilia of siloxene enhance HER activity. [ABSTRACT FROM AUTHOR]