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In this paper, NiCo2S4 was coated on the surface of WS2 of a 1T/2H mixed phase by a two-step hydrothermal method to form an in situ core–shell structure. The unique S-scheme heterojunction of the NiCo2S4@WS2 core–shell composite photocatalyst improved the easy recombination of carriers caused by the narrow band gap of NiCo2S4 and WS2, and improved the photocatalytic hydrogen production performance. The loading ratio of NiCo2S4@WS2, the addition of Eosin Y, and the pH value of TEOA were optimized. Under the optimal conditions, the hydrogen production rate reached 5.814 mmol g−1 h−1, which is about 8.55 times and 3.35 times the hydrogen evolution rates of NiCo2S4 and WS2, respectively. The composite catalyst exhibits excellent charge separation efficiency in photoelectrochemistry, PL and BET tests, carrier transport rate and large specific surface area that can provide more active sites, which are the main factors for the improvement of the hydrogen evolution performance. This paper demonstrates new design strategies to drive efficient photocatalytic hydrogen production by building in situ core–shell structures and optimizing the carrier transport paths, which will yield new insights. [ABSTRACT FROM AUTHOR]

Photoinduced electron-separation and -transport processes are two independent crucial factors for determining the efficiency of photocatalytic hydrogen production. Herein, a sulfur vacancy defect-decorated CoSx@In2S3 (CoSx@VS-In2S3) core/shell heterojunction photocatalyst was synthesized via an in situ sulfidation method followed by a liquid-phase corrosion process. Photocatalytic hydrogen evolution experiments showed that the CoSx@VS-In2S3 nanohybrids delivered an attractive photocatalytic activity of 4.136 mmol h−1 g−1 under visible-light irradiation, which was 8.23 times higher than that of the pristine In2S3 samples. As expected, VS could enhance the charge-separation efficiency of In2S3 through rearranging the electrons of the In2S3 basal plane, in addition to improving the electron-transfer efficiency, as visually verified by transient absorption spectroscopy. Mechanism studies based on density functional theory calculations confirmed that the In atoms adjacent to VS played a key role in the translation, rotation, and transformation of electrons for water reduction. This scalable strategy focused on defect engineering paves a new avenue for the design and assembly of 2D core/shell heterostructures for efficient and robust water-splitting photocatalysts. [ABSTRACT FROM AUTHOR]

The application of photocatalysts for hydrogen production is limited by their low separation efficiency and poor utilization of photogenerated electron–hole pairs. To circumvent such disadvantages, the heterojunctions have been produced to improve the separation of charges and increase the activity of photocatalysts. To date, only a few studies have been conducted to investigate the interaction between the type of heterojunction interface and the photocatalytic hydrogen evolution performance of composites. Herein, the performance of an NH2-UiO-66@MoS2 composite as a photocatalyst for hydrogen production is evaluated. Moreover, NH2-UiO-66@MoS2 heterostructures were prepared through chemical bonding (C-NUM) and physical connection (P-NUM). The photocatalytic hydrogen evolution performance of NH2-UiO-66@0.2MoS2 (C-NUM-0.2) was 1.8 and 1.14 times greater than those of NH2-UiO-66 and P-NUM, respectively. The heterojunction prepared through chemical bonding facilitated the separation of the photogenerated carriers and improved the photocatalytic stability of the composite, demonstrating its potential as a high-performance photocatalyst for hydrogen production. [ABSTRACT FROM AUTHOR]

La2Ti2O7 has been perceived as a potential photocatalytic material candidate for hydrogen evolution in recent years. However, its wide band gap brings about a narrow light absorption range and thereby results in poor photocatalytic activity. Herein, to enhance the light absorption capability, as well as promote the separation of photogenerated carriers, a CuInS2/La2Ti2O7 heterojunction photocatalyst was designed. A narrow band-gap semiconductor, CuInS2, was grown in situ on the surface of La2Ti2O7 by a solvothermal method. The effects and related mechanisms of CuInS2 loading on the photocatalytic activity were systematically investigated. The composite photocatalysts present a much better hydrogen evolution performance than the single materials. The highest hydrogen evolution rate reaches 64.41 μmol g−1 h−1. The enhancement of hydrogen evolution performance can be ascribed to the improvement of light absorption, as well as the acceleration of separation of photogenerated carriers, due to the loading of CuInS2 and the formation of a type II heterojunction between two materials. [ABSTRACT FROM AUTHOR]

The separation efficiency of photogenerated carriers is a key factor affecting photocatalytic hydrogen evolution activity. However, loading precious metals is a cost problem, so in this work cheap carbon rods are introduced into the S-scheme heterojunction of CeO2/MoO2 as electron transfer channels. The construction of the S-scheme heterojunction greatly improves the reduction activity of a single catalyst and effectively inhibits the recombination of photogenerated electrons and holes. The carbon rods at the interface between CeO2 and MoO2 can ensure the rapid transfer of space charge, thus significantly improving the separation efficiency of photogenerated carriers. The synergistic effect of these two promotes the composite catalyst's photocatalytic hydrogen evolution activity. After optimization, the photocatalytic hydrogen evolution amount of 30% CeO2/MoO2–C (6725 μmol g−1) is 18.6 and 2.43 times those of CeO2 (373 μmol g−1) and MoO2–C (2771 μmol g−1), respectively. 30% CeO2/MoO2–C showed good stability in the photocatalytic cycle experiment. Simultaneously, steady-state fluorescence and electrochemical characterization showed that the introduction of carbon rods promoted the spatial transfer of electrons. This work provides a new design idea and method for applying and developing the S-scheme heterojunction. [ABSTRACT FROM AUTHOR]

S-scheme heterojunction is a new photocatalytic hydrogen production system, which can effectively eliminate useless electron–hole pairs and improve the efficiency of photocatalytic hydrogen production. In this work, Ni-MOF-P(Ni2P)/In2O3 composite photocatalyst was prepared with Ni-MOF-74 and In2O3 by a one-step calcination-phosphating method. The prepared composite catalyst maintained a specific parallelogram-layered structure of Ni-MOF-74 and constructed S-scheme heterojunction. Various characterization techniques such as XRD, SEM, and XPS were used for the characterization of the photocatalyst, which proved that the Ni-MOF-P/In2O3 composite photocatalyst was successfully synthesized for the photocatalytic performance. SEM study showed that In2O3 was excellently compounded on Ni2P, and the cycling experiments and XRD of the sample after the cycling experiment proved their outstanding stability. The amount of hydrogen evolution with a mass ratio of Ni2P and In2O3 of 1 : 0.3 was 494.17 μmol (within 5 h), which is 3 times the hydrogen evolution of Ni-MOF-P. In this work, a novel and simple method for preparing non-noble metal phosphides was proposed for photocatalytic hydrogen evolution using a photocatalyst. [ABSTRACT FROM AUTHOR]

Rational design of an efficient hydrogen evolution reaction (HER) electrocatalyst continues to be a significant challenge for large-scale application of renewable electrochemical energy devices. Herein, an in situ interface engineering strategy is elaborately developed to construct an advanced multi-active component HER electrocatalyst, in which abundant tungsten phosphide (WP) and nickel phosphide (Ni2P) heterogeneous interfaces are synchronously encapsulated in nitrogen and phosphorus co-doped two-dimensional carbon frameworks (WP–Ni2P@NPC) via convenient solid-phase reaction and subsequent high-temperature pyrolysis. In particular, the type of solid precursor has a critical impact on the formation of a flake-like nanoskeleton and abundant WP/Ni2P heterointerfaces. Moreover, the integration of metal phosphide leads to a high graphitization degree of the carbon backbone. Benefitting from the favorable material characteristics of the nitrogen and phosphorus co-doped graphitic nanostructures, and the heterogeneous interface interaction between WP and Ni2P, WP–Ni2P@NPC possesses superior HER electrocatalytic activity to a single active component catalyst. This work offers an efficient strategy for designing efficient catalysts. [ABSTRACT FROM AUTHOR]