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The fabrication of heterojunctions is an intriguing approach to boost the reactivity of catalysts. However, facile preparation of desirable heterojunction materials remains a challenge. Here, novel CoPS3/CoS2 heterojunctions are created by an intuitive phosphatization process on the basis of structurally flexible cobalt sulfide precursors. Significant stress effect exists at these heterogeneous interfaces, resulting in lattice distortions and the exposure of more active sites. The interface interaction also modifies the catalyst's electronic structure to improve its electrical conductivity and hydrogen adsorption capabilities. Notably, the overpotential of the CoPS3/CoS2 heterojunction for electrocatalytic hydrogen evolution reaction is just 36.3 mV, which is far superior to those of single‐component catalysts and competitive with comparable catalysts reported. This work not only offers an innovative electrocatalyst but also a strategy that can be used to create heterojunctions based on related transition metal thiophosphates. [ABSTRACT FROM AUTHOR]

The construction of heterostructures is a versatile tactic to enhance catalytic activity. However, it is still elusive to realize the modulation of the interlayer spacing in this way to further improve the performance. Here, strong interfacial coupling between CoSe2 and MoSe2 by constructing CoSe2/MoSe2 heterostructures is achieved. The interlayer spacing of MoSe2 is compressed by 0.3 Å. The enhanced charge transfer is validated by X‐ray absorption spectroscopy and X‐ray photoelectron spectroscopy. Coupled with the morphology of hollow microtubes, which can facilitate the exposure of active sites, CoSe2/MoSe2 heterostructures reported here exhibit high activity (119 mV at 10 mA cm−2) and excellent stability with small degradation after 50 h operation, surpassing other analogous powdered electrocatalysts. This work sheds light on the importance of tuning the interlayer spacing to improve electrocatalytic activity. [ABSTRACT FROM AUTHOR]

The discovery and identification of novel active sites are paramount for deepening the understanding of the catalytic mechanism and driving the development of remarkable electrocatalysts. Here, we reveal that the genuine active sites for the hydrogen evolution reaction (HER) in LaRuSi are Si sites, not the usually assumed Ru sites. Ru in LaRuSi has a peculiar negative valence state, which leads to strong hydrogen binding to Ru sites. Surprisingly, the Si sites have a Gibbs free energy of hydrogen adsorption that is near zero (0.063 eV). The moderate adsorption of hydrogen on Si sites during the HER process is also validated by in situ Raman analysis. Based on it, LaRuSi exhibits an overpotential of 72 mV at 10 mA cm−2 in alkaline media, which is close to the benchmark of Pt/C. This work sheds light on the recognition of real active sites and the exploration of innovative silicide HER electrocatalysts. [ABSTRACT FROM AUTHOR]

Sluggish electron kinetics in the oxygen evolution reaction (OER) is one of the main factors restricting the development of hydrogen production technology from electrical water splitting, while the key to breaking through the bottleneck is to develop low-cost and efficient OER electrocatalysts. Here, a scheme for regulating the phase of electrocatalysts using carbon nanotubes is proposed, which significantly boosts the OER activity of transition metal complexes, exhibiting comparable electrocatalytic performance to noble metals. In this process, an organic complex of cobalt was combined with carbon nanotubes that prevent the catalyst from crystallizing during vulcanization, with sulfur atoms replacing some of oxygen atoms to further modify the active center. The as-fabricated amorphous CoOxSy complex showed excellent OER activity with a unique electronic structure, resulting in overpotentials of 290 mV and 330 mV at current densities of 10 mA cm−2 and 100 mA cm−2, respectively, and a Tafel slope of 50.8 mV dec−1. Moreover, the participation of carbon nanotubes further enhanced the electrochemical stability of the catalyst, which exhibited consistent performance in stability tests up to 60 hours. The results demonstrate the potential of carbon-based amorphous transition metal complexes as highly active electrocatalysts and provide a new possibility to design efficient catalysts by phase engineering. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Mo based nanorod arrays (NMNAs) were prepared by a one-step molten salt strategy. • This nanostructure favor the migration of bubbles and exposing more active sites. • NMNAs exhibit outstanding OER, HER, and overall water splitting activity. • The modulated electronic structures between Ni-Mo contribute to the high activity. The exploration of low-cost, high-efficient and robust bifunctional electrocatalysts for water splitting is urgently desired for developing clean hydrogen energy conversion technology. In this work, we present a facile and effective one-step molten salt synthesis tactics to prepare self-supported 1D Ni-Mo based mixed-phase polyionic compounds nanorod arrays (NMNAs). Due to the exposed more active sites of this nanostructure and accelerated charge transfer derived from modulated electronic structures between Ni-Mo, the as-fabricated NMNAs electrodes deliver remarkable bifunctional electrocatalytic water splitting performance, with overpotential values of 234.2 mV at 200 mA cm−2 and 191.2 mV at 100 mA cm−2 in 1 M KOH for OER and HER, respectively. Furthermore, the alkaline electrolyzer composed of NMNAs needs a low overall-water-splitting cell voltage of 1.423 V to drive a current density of 10 mA cm−2. This work will shed light on the preparation of other related self-supporting nanostructured bifunctional electrocatalysts with excellent performance. [ABSTRACT FROM AUTHOR]