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Monoclinic scheelite bismuth vanadate is an efficient photocatalyst for water splitting. In this paper, we perform DFT + U calculations to investigate the structural, electronic, and optical properties, water adsorption and the oxygen evolution reaction processes on BiVO4 (001) and BiVO4 (110) surfaces in acidic medium both in the gas and solution (water) phases. The structural, electronic, optical, and water adsorption properties reveal that BiVO4 (001) surface is energetically more stable than BiVO4 (110) surface in vacuum. On other hand, the water oxidation mechanisms reveal that BiVO4 (110) surface in water and in strained form in vacuum is energetically more stable than BiVO4 (001) surface in water and in strained form in vacuum both U = 0 and 2.1 V. The free energy of adsorption for all systems at U = 2.1 V reduce about 2 times than that at U = 0 V. Such analyzes provide important insights into the role of different facets on BiVO4 surface for photocatalytic reactions. [ABSTRACT FROM AUTHOR]

Nitrogen doped carbon functionalized CoSe2 nanowires (CoSe2@N–C NWs), which act as potential oxygen evolution reaction (OER) catalysts with a large current density and high stability have been reported. Owing to the collaborative optimization of electrical conductivity, free adsorption energy and binding strength of OER intermediates, the prepared CoSe2@N–C NWs exhibit an enhanced 6.61-fold catalytic activity compared to the pristine CoSe2 NW electrode in 1.0 M KOH solution at the overpotential of 340 mV. [ABSTRACT FROM AUTHOR]

The development of active and inexpensive electrocatalysts for the oxygen evolution reaction (OER) to promote water splitting has always been a major challenge. Cobalt‐based oxides and sulfides have been actively investigated due to their low cost and high activity. However, the lower intrinsic conductivity of cobalt oxide and the inferior stability of cobalt sulfides still limit their practical application. Herein, CoO was chosen for a proof‐of‐concept study in which the anion‐doping strategy was used to obtain an excellent catalyst. Sulfur incorporation optimizes the charge‐transfer properties and active sites of sulfur‐doped CoO (S‐CoO) and thus gives rise to improved catalytic activity. Besides sulfur doping, the stable framework of the cobalt oxide was well maintained, and thus high stability of S‐CoO throughout the reaction process was ensured. Nanoflake electrocatalyst: Sulfur‐doped CoO nanoflakes with loosely packed structure were fabricated by reaction of Co3O4 nanosheets with thioacetamide (TAA) which was used as both sulfur source and reducing agent (see figure). Sulfur doping optimizes the charge‐transfer properties and the active sites and thus leads to clearly enhanced catalytic activity in the oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

Observation of novel linear relationship between Δ G OOH and Δ E H suggests Δ E H as a simple descriptor for rational design of HER/ORR bifunctional graphyne materials. [Display omitted] The high cost and relative scarcity of platinum (Pt) restrict large-scale commercialization of fuel cells, which has spurred researchers to develop low-cost alternatives integrating with high hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) catalytic activity. Herein, we performed density functional theory (DFT) calculations to explore the electrocatalytic activity of graphyne nanotubes (GyNTs). Several GyNTs were found to be potential metal-free electrocatalysts, with both HER and ORR activity superior to Pt. Moreover, we revealed a linear relationship between the Gibbs free energy change of O 2 adsorption (Δ G OOH) and binding energy of H adsorption (Δ E H), which could be attributed to the fact that both the C O bond of OOH adsorption and the C H bond of H adsorption are single bonds. Therefore, Δ E H is proposed as a general descriptor for the rational design of bifunctional graphyne materials toward HERs and ORRs. Our findings provide a simple strategy for the rational design of bifunctional materials. [ABSTRACT FROM AUTHOR]

Abstract DFT calculations are performed to investigate the water oxidation reaction intermediates on Ag 2 M (M = Fe, Co, Ni, Cu), and Pt 3 clusters in alkaline media both in the gas and solution (water) phases in the neutral and charged states. The calculated results revealed that the neutral and anionic clusters were found to be more suitable catalysts than cationic clusters because of weakly bonded water oxidation reaction intermediates. In addition, the calculated structural parameters of the water oxidation intermediates with Ag 2 M (M = Fe, Co, Ni, Cu) clusters revealed that M-OH bond strengths are found to be in the order of Cu < Ni < Co < Fe. Conclusively, Ag 2 Cu cluster was determined to be the best electrocatalyst regarding oxygen evolution reaction via 4e transfer, which is consistent with results on larger Ag 2 M clusters (13 atoms) and periodic Ag-M nanoalloys due to weaker binding energies of the water oxidation intermediates. Highlights • Ag 2 M (M = Fe, Co, Ni, Cu), and Pt 3 clusters were considered as electro-catalysts for OER. • Neutral and anionic clusters were found to be more suitable catalysts than cationic clusters. • M OH bond strengths are found to be in the order of Cu < Ni < Co < Fe. • Ag 2 Cu cluster was determined to be the best electrocatalyst regarding oxygen evolution reaction via 4e transfer. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MOFs-deriver N-doped CoC x /FeCo@C/rGO was synthesized as a catalyst for ORR. • The ORR activity of N-doped CoC x /FeCo@C/rGO was higher than that of the Pt/C. • The OER activity of N-doped CoC x /FeCo@C/rGO was higher than that of the RuO 2. • The synergistic effect of CoC x /FeCo and N-doped carbon results in the activity. Abstract Metal-organic framework derived materials have a great promise as non-precious metal-based electrocatalysts for large-scale applications of energy storage and transition devices with low-cost and high efficiency. Here, we report a high performance core-shell-structured nitrogen-doped CoC x /FeCo@C/reduced graphene oxide (rGO) hybrid, which is derived from Fe-doped Co 3 [Co(CN) 6 ] 2 MOFs, as bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Structure characterizations show that the carbon shell of CoC x /FeCo and graphene support are bonded to each other, which offer a large surface area and stable anchoring sites for the CoC x /FeCo. Electrochemical tests show that N-doped CoC x /FeCo@C/rGO hybrid exhibits superior onset potential (1.0183 V vs RHE), half-wave potential (0.9653 V vs RHE), peak current intensity (0.9233 mA/cm−2) and long-term durability for ORR than those of Pt/C (onset potential, half-wave potential and peak current intensity are 1.0174 V and 0.9213 V, 0.8233 mA/cm−2, respectively) in 0.1 M KOH electrolyte. The overpotential of the hybrid for OER is only ∼390 mV at a current intensity of 10 mA/cm−2, which is close to that of the RuO 2. The excellent electrocatalytic properties of this hybrid make it a great potential to be substitute for precious-based catalysts for ORR and OER in fuel cells and water splitting. [ABSTRACT FROM AUTHOR]

The sluggish oxygen evolution reaction (OER) limits the efficiency of overall water splitting, which thereby hinders hydrogen evolution reaction (HER). Here, we demonstrate a bifunctional CoNiP nanosheet integrated electrode (CoNiP-NIE) to boost HER and replace OER by 5-hydroxymethylfurfural oxidation reaction (HMFOR) to obtain high-valued 2,5-furandicarboxylic acid (FDCA). The as-developed CoNiP-NIE exhibits a constant high Faradaic efficiency more than 82% for HMFOR in a wide potential from 1.40 V to 1.70 V vs. RHE, which stand at the top level among the reported electrocatalysts. Moreover, the low overpotential for HER further indicates its high efficiency in the H 2 generation. Based on the bifunctional activity of CoNiP, an electrochemical hydrogen evolution coupled with biomass oxidation device is constructed, which delivers lower voltage (1.46 V) for anode oxidation and higher evolution rate of H 2 (41.2 L h−1 m−2) than water splitting (1.76 V, 16.1 L h−1 m−2). We report a bifunctional CoNiP nanosheet integrated electrode by facile ion etching and subsequent phosphidation process, which shows promising activity for HMFOR and HER simultaneously. This work thus could provide a successful paradigm for rational design bifunctional electrocatalysts for highly efficient hydrogen production coupled with biomass oxidation. [Display omitted] • The CoNiP-NIE exhibits high FE FDCA in a wide potential from 1.40 to 1.70 V vs. RHE. • An EHCO device based on bifunctional CoNiP-NIE enhances the evolution rate of H 2. • CoNiP displays moderate desorption for FDCA and enhanced electrical conductivity. [ABSTRACT FROM AUTHOR]

• Few-layered ReSe 2 nanoflakes are vertically arranged on rGO. • Mechanism of vertical growth of ReSe 2 on rGO is clarified by DFT calculation. • Plentiful exposed edges/corners on ReSe 2 facilitate the generation of active sites for electrocatalysis. • Improved electrical conductivity and electrochemical stability of ReSe 2 are realized after hybrid with rGO. • Prominent HER performance is measured with a low overpotential and small Tafel slope. Hydrogen evolution reaction (HER) by water splitting has made a significant contribution to producing large amounts of hydrogen gas as the next generation fuel. Development of highly efficient, economically viable, and electrochemically stable HER electrocatalysts has accordingly become a prerequisite for practical implementation of large scale water electrolysis. Mono/few-layered transition metal dichalcogenide (TMD) based HER-electrocatalysts have recently garnered great interest due to their diverse tunable electrochemical properties. However, they still face intrinsic limitations such as self-aggregation, rare active sites, high electrical resistance, and long-term electrochemical instability. To tackle these challenges, we designed and synthesized a novel electrocatalyst comprising active site-rich rhenium diselenide (ReSe 2) nanoflakes perpendicularly anchored on a reduced graphene oxide (rGO) nanosheet support via a facile one-step hydrothermal synthesis. The rGO support provides a growing platform for few-layered ReSe 2 nanoflakes while facilitating plentiful exposure of edge/corner sites of ReSe 2 , highly desirable for maximizing the catalytic activity of ReSe 2 @rGO. The synthesized ReSe 2 @rGO exhibits a low overpotential of 145.3 mV at a current density of 10 mA·cm−2 with a Tafel slope of 40.7 mV·dec−1 for the HER process due to the synergistic combination of high surface density of unsaturated coordination sites, remarkably accelerated electron transfer, and enhanced electrochemical stability. This outcome suggests using structurally regulated hybridization of TMDs and graphene as a platform toolkit for developing high performance HER catalysts. [ABSTRACT FROM AUTHOR]