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In this work, a highly efficient Pd catalyst containing gallium oxides supported on reduced graphene oxides has been synthesized by sodium borohydride reduction method for the electro-oxidation of formic acid. The synthesized Pd x Ga y /rGOs display outstanding electrocatalytic activity with considerably higher surface area and improved electrical conductivity during formic acid oxidation as compared to Pd/C. According to the electrochemical results the Pd 6 Ga 4 /rGO showed significantly higher electrochemical surface area (102.4 m2/g), improved catalytic activity (86 mA/cm2), smaller Tafel slope value (121 mV dec−1) and excellent durability during the electrocatalytic formic acid oxidation. Th higher turnover frequency of Pd 6 Ga 4 /rGO (4.2 × 10−1) further validates its better electrocatalytic activity. This work proves that adding gallium oxides to palladium-based electrocatalysts increases electrical conductivity and causes the uniform dispersion of palladium nanoparticles on reduced graphene oxide surface. • Gallium oxide promoted Pd electrocatalysts (Pd x Ga y /rGO) are synthesized. • Pd x Ga y /rGO electrocatalysts are investigated for formic acid oxidation reaction. • Adding gallium oxide to the Pd/rGO electrocatalyst boosts the electrochemical activity. • Pd 6 Ga 4 /rGO shows catalytic activity of 86 mA/cm2 and a Tafel slope value of 121 mV dec−1. • Pd 6 Ga 4 /rGO demonstrates high CO tolerance and great stability. [ABSTRACT FROM AUTHOR]

Abstract Confining polyoxometalates inside the cavities of metal-organic frameworks is a method to utilize these versatile molecular metal oxide clusters as quasi-heterogeneous catalysts and to thereby broaden their applications. In this study, manganese-polyoxomolybdate anions of the Keggin structure type, [PVMoVI 11 MnII(H 2 O)O 39 ]5– (Mn-POM), are encapsulated in an iron(III)-based metal-organic framework (MIL-100) to achieve 30 wt.-% loaded Mn-POM /MIL-100 composite material (1). The composite compound 1 displays excellent catalytic activity for the selective reduction of p-nitrophenol into p-aminophenol (96%) at 20 °C in 25 min. The rate constant and catalyst activity are calculated as 0.10 min–1 and 328 L g–1 s–1, respectively. Interestingly, both individual components of the composite material are themselves inactive toward this reaction. Graphical abstract The synergism between a Keggin-type manganese-polyoxomolybdates and MIL-100 (Fe) turns the two individual inactive components into an active POMMOF composite ([PVMoVI11MnII(H 2 O)O 39 ]5–@MIL-100) catalyst toward reduction of p-nitrophenol. fx1 [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition metal nitrides (TMNs) have gained substantial interest to catalyse water splitting reaction. • Iron and nickel based TMNs are considered as ideal electrocatalysts because of the abundance, low cost, and high catalytic activity. • Single phase TMNs have unsatisfactory performance due to inadequate M−H/M−OH bond strength. • Recent developments pertaining to Fe and Ni-based TMNs are presented for electrochemical water splitting. Transition metal nitrides (TMNs) have gained substantial interest to generate hydrogen from direct dissociation of water via catalytic strategy. Due to the unique noble metal like structure, high electric conductivity, corrosion resistance, broad pH stability and probable structural modifications TMNs are gauged as efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting (OWS) electrocatalysts. Iron and nickel based TMNs are considered as ideal electrocatalysts because of the abundance, low cost and high catalytic activity as compared to the expensive benchmark catalysts. However, the single phase TMNs have unsatisfactory performance due to inadequate M−H/M−OH bond strength. Most researchers have focused in designing advanced heterostructures by doping other metals, metallic compounds, and conductive substrates to improve catalytic performance due to the tailored electronic structure to modify M−H/M−OH bond strength, boost electrochemical stability and synergistic effects. In this review, we highlight the recent developments pertaining to Fe and Ni-based TMNs from the stance of advanced nanoarchitecture electrocatalysts for electrochemical water splitting. The key challenges and future perspectives confronting expansion of water splitting catalysts are critiqued. [ABSTRACT FROM AUTHOR]

Research on water splitting reaction is on priority to explore an alternative source of energy with little to no carbon emissions. Among the two half reactions of electrochemical water splitting, oxygen evolution reaction (OER) is highly desirable yet challenging to prepare a cost effective and viable electrocatalyst to boost the OER activity. Herein, we have prepared a novel electrocatalyst, CoO x -CoP/N-CNTs, by the phosphidization of cobalt oxides (CoO x) encapsulated N- doped carbon nanotubes (CoO x /N-CNTs). The CoO x /N-CNTs composite is derived via pyrolysis of cobalt based zeolitic imidazole framework (ZIF-12) at 950 °C under argon atmosphere. The CoO x /N-CNTs is phosphidized at various temperatures ranging from 320 °C to 400 °C. The optimized temperature to attain the best catalytic activity is 380 °C. The phosphatized material, CoO x -CoP/N-CNTs, shows superior performance towards OER with an overpotential of 250 mV @ 20 mAcm−2 vs 532 mV @ 20 mAcm−2 of un-phosphidized material, CoO x /N-CNTs, which shows significant effect of phosphidization. The maximum current density of 160 mAcm−2 in 1 M KOH solution is achieved. • A novel electrocatalyst, CoO x -CoP/N-CNTs, is fabricated. • The phosphatized material, CoO x -CoP/N-CNTs, shows superior performance towards OER. • During OER activity, an overpotential of 250 mV at 20 mAcm−2 and current density of 160 mAcm−2 is observed. • The electrochemical activity remarkably greater than the un-phosphatized material. [ABSTRACT FROM AUTHOR]

Transition metal oxyhydroxides have been used as promising electrocatalysts for water splitting however, their catalytic activity is restricted due to low surface area and poor conductivity. Herein, we report novel composite FeOOH@ZIF-12/graphene composite as electrocatalyst for water oxidation, whereby ZIF-12 provide extra surface for the FeOOH dispersion whilst graphene act as excellent electron mediator. The composite shows a low overpotential value of 291 mV to attain a current density of 10 mA cm−2 and a low Tafel slope value of 78 mV dec−1. The catalyst offers a maximum current density of 101 mA cm−2, while it gives a turnover frequency (TOF) value of 0.031 s−1 at an overpotential of 291 mV only. The excellent activity and remarkable stability of composite is attributed to highly conductive and porous support. [Display omitted] • FeOOH nanoparticles are incorporated in ZIF-12/graphene matrix. • The synthesized composite is utilized as electrocatalyst for water oxidation. • The composite shows a low overpotential value of 291 mV @ 10 mA cm−2. • The catalyst offers a maximum current density of 101 mA cm−2 with a TOF value of 0.031 s−1. [ABSTRACT FROM AUTHOR]

Au nanoparticles of size ranging 2–6 nm were deposited over hexagonal CdS using three conventional metal deposition methods namely; deposition precipitation (DP), incipient wet impregnation (WI), photo-deposition (PD) and a recently reported KI method by our group [1]. The later involves reduction of Au 3+ ions with iodide ions. XRD results confirmed the formation of CdS hexagonal phase from as prepared cubic phase at 600 °C under the N 2 atmosphere. Transmission electron spectroscopy (TEM), diffused reflectance spectroscopy (DRS), X-Ray fluorescence (XRF), ICP-OES and photoreactions were conducted to study the effect of Au particle size, Au loading and Au plasmonic properties on H 2 production activity. It was found that surface plasmon resonance (SPR) is directly linked to Au particle size. Among all four methods, 3 wt.% Au deposited over hexagonal CdS by KI method with mean Au particle size of 4 nm showed highest performance for hydrogen production from water electrolyte mixture under visible light irradiation (>420 nm and a flux of 35 mW/cm 2 ). XPS results of Au/CdS prepared by KI method showed that Au is exclusively present in zero oxidation state before and after photocatalytic H 2 production testes indicating the stable nature of Au/CdS catalyst. The H 2 production activity of Au/CdS catalysts prepared by different metal deposition methods and H 2 production mechanism in a water-electrolyte is discussed in detail. [ABSTRACT FROM AUTHOR]

• A rare structural topology based on copper hydroxide layers is observed in [Cu 3 (OH) 4 (oba)] n (1). • Compound 1 exhibits excellent water oxidation catalysis activity in basic solution. • Chronoamperometric studies show that 1 reaches a current density of 0.1 mA cm−2 at η = 576 mV. • Catalyst 1 showed a turnover frequency (TOF) of 2 × 10−3 s−1 at 418 mV. • Compound 1 retains its structural integrity during catalytic reactions. An uncommon copper(II) hydroxide layer-based coordination polymer [Cu 3 (OH) 4 (oba)] n (1) (oba = 4,4′-oxybisbenzoate) has been synthesized and tested as electro-catalyst for water oxidation under basic conditions. In comparison to classical Cu(OH) 2 , 1 exhibits improved thermal stability of up to ca. 350 °C. Chronoamperometry studies indicate that catalyst 1 reaches an anodic current density of 0.1 mA cm−2 at η = 576 mV; a TOF of 2 × 10−3 s−1 at 418 mV overpotential value. The catalyst 1 shows Faradaic efficiency of 95%. Long-term catalytic studies for 10 h at a constant potential of 1.2 V indicate that compound 1 is robust and retains its chemical composition. Infrared spectroscopy, powder X-ray diffraction analysis, X-ray photoelectron spectroscopy and cyclic voltammetry studies of the pristine and post-catalytic compound 1 -coated FTO electrodes further confirm that 1 retains its structural integrity throughout the catalytic cycle. Our results represent a proof-of-concept for designing next-generation robust and improved OER electrocatalysts based on earth-abundant metals. [ABSTRACT FROM AUTHOR]