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Ceria-supported Pd single-atom catalysts (SACs) are important catalysts to catalyze the CO oxidation, often used in three-way catalysts to treat automobile exhaust gases. This paper uses density functional theory (DFT) calculations and transition state theory to systematically study the effect of Ga atom doping on the performance of the Pd/CeO 2 SACs system. Noticeably, the results of DFT calculations reveal that the stability of Pd single atoms supported on the surface of CeO 2 (111) was significantly augmented by doping Ga. An oxygen vacancy generated easily near the Ga and Pd site will act as a crucial role for activating the adsorbed oxygen molecule. Most importantly, the climbing image nudged elastic band (CINEB) calculations show that the doping of Ga remarkably reduces the highest energy barrier during the CO oxidation reaction, meaning that the catalytic performance of the CO oxidation reaction is promoted effectively. This work provides a new perspective for SACs modification. [Display omitted] • Ga-doped Pd/CeO 2 single-atom catalysts with oxygen vacancies are studied in detail. • The stability of Pd single-atom has been enhanced by doping Ga. • O 2 can be further activated at the oxygen vacancies formed by doping Ga. • Ga-doped Pd/CeO 2 possesses higher catalytic activity for CO oxidation. [ABSTRACT FROM AUTHOR]

The coupling of two-dimensional (2D) layered materials is an effective way to realize photocatalytic hydrogen production. Herein, using first-principles calculations, the photocatalytic properties of GaN/CNs heterojunctions formed by two different graphite-like carbon nitride materials and GaN monolayer are discussed in detail. The results show that the GaN/C 2 N heterojunction can promote the effective separation of photogenerated electron and hole pairs, which is attributed to its type-II band orientation and high carrier mobility. However, the low overpotential of GaN/C 2 N for photocatalytic hydrogen production limits the photocatalytic performance. On this basis, we adjust the CBM position of the GaN/C 2 N heterojunction by applying an electric field to enhance its hydrogen evolution capability. In addition, the GaN/g-C 3 N 4 is a type-I heterojunction, which is suitable for the field of optoelectronic devices. This work broadens the field of vision for the preparation of highly efficient photocatalysts. [Display omitted] • The establishment of the GaN/C 2 N type-II heterojunctionhas high carrier mobility. • Applying an electric field is effective to adjust the bandgap and redox potential of the GaN/C 2 N heterojunction. • The GaN/g-C 3 N 4 heterojunction has the advantage of being used in optoelectronic devices. • This work broadens the field of vision for the preparation of highly efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Researches on environmentally friendly semiconductor photocatalysts for efficient photocatalytic hydrogen evolution have important practical significance. Here, using first-principles calculations, the CeO 2 (111)/hBN heterojunction was conceived. The influence of the interface effect on the structural, electronic and optical properties of the heterojunction was investigated in detail. The band gap of the heterojunction is smaller than the two individual components and forms a type-II heterojunction, improving the photocatalytic activity. Furthermore, by doping two C atoms, the band gap of heterojunction was further narrowed. Both the oxidation and reduction potential of CeO 2 (111)/hBN heterojunction meet the requirements of water splitting and has certain advantages over other photocatalysts in the ability for photocatalytic hydrogen evolution. The study revealed the possible mechanism of CeO 2 (111) and hBN monolayers compositing to facilitate photocatalysis and hydrogen evolution ability, which may provide a possible reference direction for the practical design of more high-quality semiconductor photocatalysts. [Display omitted] • CeO2(111)/hBN forms type-Ⅱ heterojunction. • CeO2(111)/hBN has good thermodynamic stability and mechanical stability. • CeO2(111)/hBN has certain advantages in photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

The design and development of low-cost, abundant reserves, high catalytic activity and durability bifunctional electrocatalysts for water splitting are of great significance. Here, simple hydrothermal and hydrogen reduction methods were used to fabricate a uniform distribution of Fe-doped MoO 2 /MoO 3 sheets with abundant oxygen vacancies and heterojunctions on etched nickel foam (ENF). The Fe– MoO 2 /MoO 3 /ENF exhibited a small overpotential of 36 mV at 10 mA cm−2 for hydrogen evolution reaction (HER), an excellent oxygen evolution reaction (OER) overpotential of 310 mV at 100 mA cm−2 and outstanding stabilities of 95 h and 120 h for the HER and OER, respectively. As both cathode and anode catalysts, the heterogeneously structured Fe– MoO 2 /MoO 3 /ENF required a low cell voltage of 1.57 V at 10 mA cm−2. Density functional theory (DFT) calculations show that Fe doping and MoO 2 /MoO 3 heterojunctions can significantly reduce the band gap of the electrode, accelerate electron transport and reduce the potential barrier for water splitting. This work provides a new approach for designing metal ion doping and heterostructure formation that may be adapted to transition metal oxides for water splitting. Image 1 • Improve the adhesion of the materials by etching nickel foam (NF). • Two-step reaction simultaneously achieves iron doping and heterojunctions. • DFT calculations confirm that Fe doping increased the conductivity. • In situ grown heterojunctions greatly reduce the potential barrier. [ABSTRACT FROM AUTHOR]

• The structural folds in g-C3N4 is good for enhancing the photocatalytic activity. • SWCNTs modified g-C3N4 have better overall HER performance than pure g-C3N4. • SWCNTs/g-C3N4 have significantly enhanced visible light absorption. • The semiconductor SWCNTs can better improve the photocatalytic performance of g-C 3 N 4. Single-walled carbon nanotubes (SWCNTs) modified g-C 3 N 4 nanocomposites have attracted extensive attention due to their good photocatalytic activity for water splitting in the visible region, but the theoretical research on the enhancement mechanism is still lacking. Using first-principles hybrid density functional calculations, the potential photocatalytic enhancement mechanism of SWCNTs-modified g-C 3 N 4 has been studied in detail. For different metal (9,0) and semiconductor (10,0) SWCNTs modified patterns, the two components are always linked by van der Waals forces without exception. Obvious structural folds in g-C 3 N 4 , large interlayer charge transfer, significantly enhanced visible light absorption, and smaller |ΔG H* |, these factors enhance the photocatalytic activity of SWCNTs/g-C 3 N 4. Interestingly, (10,0) SWCNT have better coordination advantage with g-C 3 N 4 than (9,0) SWCNT, resulting in (10,0) SWCNT/g-C 3 N 4 nanocomposite with more visible structural folding for more stable structures, greater charge transfer, and more efficient visible light absorption spectra. Moreover, we also studied the photocatalytic performance of g-C 3 N 4 modified by metal (6,0) and semiconductor (7,0) SWCNTs. As a result, the photocatalytic performance of the latter is significantly better than the former, which further shows that the semiconductor SWCNTs-modified g-C 3 N 4 maybe more superior. The findings pave the way for the development of highly active g-C 3 N 4 -based photocatalysts. [ABSTRACT FROM AUTHOR]

Bare nonprecious metal oxides are generally considered to have low HER activity, but they have the advantages of abundant resources and low cost. Herein, a facile strategy to construct abundant oxygen vacancies with heterogeneous structures of oxygen-vacancies CoFe 2 O 4 /oxygen-vacancies cobalt oxides/nickel foam (Ov-CoFe 2 O 4 /CoO x /NF) is developed using gas-phase cation exchange. Benefiting from abundant oxygen vacancies, the strong interfacial coupling effects between oxygen-vacancies CoFe 2 O 4 (Ov-CoFe 2 O 4) and oxygen-vacancies cobalt oxides (Ov-CoO x), a nanorod structure and the highly conductive nickel foam support, Ov-CoFe 2 O 4 /CoO x /NF exhibits a low overpotential of 59 mV and achieved a current density of 10 mA cm−2 in a 1 M KOH solution. Ov-CoFe 2 O 4 /CoO x /NF//Ov-CoFe 2 O 4 /CoO x /NF exhibits a low water splitting voltage of 1.51 V at 10 mA cm−2. Density functional theory calculations suggest that oxygen vacancy and interfacial coupling effects can both improve conductivity of electrocatalysts. This study provides a facile design for simultaneous realization of oxygen vacancy modification and heterostructure, which may become a simple strategy to use oxides to improve HER performance. Image 1 • A simple strategy to achieve oxygen vacancy modification and a heterostructure. • Synergistic effect lead to excellent alkaline HER activity. • 3D self-supported binder-free integrated electrode. • An effective strategy to improve oxides HER performance. [ABSTRACT FROM AUTHOR]