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We report electrocatalytic decarboxylation (ECDX) of valeric acid into paraffins, olefins, and alcohols via (non-)Kolbe electrolysis on electrodes with RuO 2 and Pt nanoparticles (NPs) as a greener alternative to thermocatalytic decarboxylation. The turnover frequency of ECDX increases, while the specific activity peaks as RuO 2 NP size increases. These opposing trends make the particle size of ∼ 12 nm the optimum size for ECDX on RuO 2. Bulk Pt was active for ECDX, while Pt NPs were only active for the oxygen evolution reaction under our conditions. ECDX current efficiency remained constant in the studied potential range on RuO 2 NPs. Esterification was the favored reaction at 2.5 V vs. RHE; however, Kolbe electrolysis was the favored reaction at the expense of the esterification at 4.5 V vs. RHE. This work highlights the performance of nanostructured materials as an alternative to bulk materials as anodes for oxidative upgrading of carboxylic acids. [Display omitted] • RuO 2 nanoparticles (NPs) are a great alternative to bulk Pt for electrocatalytic decarboxylation (ECDX). • As RuO 2 NPs size increases, the turnover frequency of ECDX increases, while the specific activity reaches a maximum. • Bulk Pt is active for ECDX, while Pt NPs are only active for the oxygen evolution reaction due to surface oxidation. • Increasing potential shifts the product selectivity of ECDX from esters to paraffin production over RuO 2 NPs. [ABSTRACT FROM AUTHOR]

The electrocatalytic oxygen evolutionreaction (OER) is a criticalanode reaction often coupled with electron or photoelectron CO2reduction and H2evolution reactions at the cathodefor renewable energy conversion and storage. However, the sluggishOER kinetics and the utilization of precious metal catalysts are keyobstacles in the broad deployment of these energy technologies. Herein,inexpensive supported 4 nm Ni–Fe nanoparticles (NiyFe1–yOx/C) featuring amorphous structures have been preparedvia a solution-phase nanocapsule method for active and durable OERelectrocatalysts in alkaline electrolyte. The Ni–Fe nanoparticlecatalyst containing 31% Fe (Ni0.69Fe0.31Ox/C) shows the highest activity, exhibitinga 280 mV overpotential at 10 mA cm–2(equivalentto 10% efficiency of solar-to-fuel conversion) and a Tafel slope of30 mV dec–1in 1.0 M KOH solution. The achievedOER activity outperforms NiOx/C and commercialIr/C catalysts and is close to the highest performance of crystallineNi–Fe thin films reported in the literature. In addition, aFaradaic efficiency of 97% measured on Ni0.69Fe0.31Ox/C suggests that carbon support corrosionand further oxidation of nanoparticle catalysts are negligible duringthe electrocatalytic OER tests. Ni0.69Fe0.31Ox/C further demonstrates high stabilityas there is no apparent OER activity loss (based on a chronoamperometrytest) or particle aggregation (based on TEM image observation) aftera 6 h anodization test. The high efficiency and durability make thesesupported amorphous Ni–Fe nanoparticles potentially applicablein the (photo)electrochemical cells for water splitting to make H2fuel or CO2reduction to produce usable fuelsand chemicals. [ABSTRACT FROM AUTHOR]

• Pt foil and thin films (TFs) of RuO 2 and IrO 2 are active for electrocatalytic decarboxylation (ECDX) of valeric acid at ambient conditions. • Rates of ECDX and O 2 evolution increase with potential, while the ECDX selectivity depends also on anode composition. • RuO 2 -TF is selective toward non-Kolbe products while Pt is selective toward Kolbe products. • The ECDX activity of RuO 2 -TF is similar to that of Pt foil per geometric area but is one order of magnitude more active per gram of metal. • Turnover frequencies of ECDX were at least one order of magnitude higher than thermocatalytic decarboxylation at 300 °C. The electrocatalytic upgrading of carboxylic acids, abundant biomass-derived molecules, remains a challenging task. Herein, we report an electrocatalytic decarboxylation (ECDX) approach for the conversion of carboxylic acids into paraffins, olefins, and alcohols via (non-)Kolbe electrolysis on thin films (TFs). The ECDX rate, product selectivity, and current efficiency were potential and electrode dependent. For example, the ECDX activity of RuO 2 -TF was similar to that of Pt foil, but the selectivity to Kolbe products was lower on the former. RuO 2 -TF showed about five times higher rates for the oxygen evolution reaction than Pt foil, which resulted in lower current efficiency. The ECDX and O 2 evolution activities of IrO 2 -TF were potential dependent, but this electrode was selective to non-Kolbe products with low current efficiency (<10 %). This work highlights the performance of thin films as an alternative to bulk metals as anodes for oxidative upgrading of carboxylic acids. [ABSTRACT FROM AUTHOR]

The performance of Zn-Air battery (ZAB) is often limited by sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reactions (OER). In this work, a flower-like porous carbon is designed for the synthesis of the Co/Zn/Mn@NC. Due to a highly porous structure and abundant active sites, the as-prepared Co/Zn/Mn@NC-800 shows a half-wave potential of 0.86 V for ORR, and an overpotential of 360 mV for OER at 10 mA/cm2, suggesting an excellent bifunctional catalytic activity. The ZAB with Co/Zn/Mn@NC-800 delivers a power density of 163 mW/cm2 and a specific capacity of 832 mA h/g Zn , higher than that with Pt/C + RuO 2 (147 mW/cm2 and 802 mA h/g Zn). Moreover, the Co/Zn/Mn@NC-800-based ZAB has a superior long-term stability with a negligible decline of efficiency (0.3%) after 534 cycles (>150 h). These results suggest that the synthesized Co/Zn/Mn@NC catalyst has a great potential for the practical application in ZABs. [Display omitted] • Flower-like porous carbon for the synthesis of trimetallic Co/Zn/Mn@NC. • The Co/Zn/Mn@NC-800 shows a half-wave potential of 0.86 V for ORR. • The Co/Zn/Mn@NC-800 has an overpotential of 360 mV for OER at 10 mA/cm2. • Zinc-air battery with Co/Zn/Mn@NC-800 has a power density of 163 mW/cm2. • The Co/Zn/Mn@NC-800-based zinc-air battery has a superior long-term stability. [ABSTRACT FROM AUTHOR]

Electrocatalyst design is an important approach to prompt the commercialization of water electrolysis technologies. In this work, a ruthenium doped MoS2/AB heterostructure is synthesized as an electrocatalyst for the hydrogen evolution reaction (HER) through hydrothermal and annealing processes. The physical–chemical characterization studies show that the MoS2/AB heterostructure and the incorporation of Ru effectively induce a phase transition from 2H to 1T-MoS2. The as-prepared Ru-MoS2/AB exhibits an excellent HER performance with a very low overpotential of 13 mV at 10 mA cm−2 and a Tafel slope of 31 mV dec−1 in 0.5 M H2SO4, remarkably higher than those of Pt/C (overpotential of 28 mV at 10 mA cm−2, 41 mV dec−1). Density functional theory calculations suggest that the H absorption on Ru bonding to S exhibits a rather low binding energy (−0.22 eV), indicating the optimum active sites of Ru near S for HER. Significantly, the Ru-MoS2/AB also demonstrates high stability under long-term discharge and elevated temperature conditions. These results suggest that the as-prepared Ru-MoS2/AB can be a promising alternative to Pt/C for water electrolysis, due to its high HER activity, easy synthesis, and good stability. [ABSTRACT FROM AUTHOR]

[Display omitted] Anodic urea oxidation reaction (UOR) is an intriguing half reaction that can replace oxygen evolution reaction (OER) and work together with hydrogen evolution reaction (HER) toward simultaneous hydrogen fuel generation and urea-rich wastewater purification; however, it remains a challenge to achieve overall urea electrolysis with high efficiency. Herein, we report a multifunctional electrocatalyst termed as Rh/NiV-LDH, through integration of nickel-vanadium layered double hydroxide (LDH) with rhodium single-atom catalyst (SAC), to achieve this goal. The electrocatalyst delivers high HER mass activity of 0.262 A mg−1 and exceptionally high turnover frequency (TOF) of 2.125 s−1 at an overpotential of 100 mV. Moreover, exceptional activity toward urea oxidation is addressed, which requires a potential of 1.33 V to yield 10 mA cm−2, endorsing the potential to surmount the sluggish OER. The splendid catalytic activity is enabled by the synergy of the NiV-LDH support and the atomically dispersed Rh sites (located on the Ni-V hollow sites) as evidenced both experimentally and theoretically. The self-supported Rh/NiV-LDH catalyst serving as the anode and cathode for overall urea electrolysis (1 mol L−1 KOH with 0.33 mol L−1 urea as electrolyte) only requires a small voltage of 1.47 V to deliver 100 mA cm−2 with excellent stability. This work provides important insights into multifunctional SAC design from the perspective of support sites toward overall electrolysis applications. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) generally exists in electrochemistry‐enabled applications that are coupled with cathodic reactions like hydrogen evolution, carbon dioxide reduction, ammonia synthesis, and electrocatalytic hydrogenation. The OER heavily impacts the overall energy efficiency of these devices because the sluggish OER kinetics result in a huge overpotential, thus, a large amount of efficient catalysts are needed. The benchmark iridium and ruthenium (Ir/Ru)‐based materials (mostly used in acid media) are, however, significantly limited by their scarcity. Non‐precious metal‐based catalysts (NPMCs) have emerged as the most promising alternatives; however, they tend to degrade quickly under the harsh operating conditions of typical OER devices. Another challenge is the unsatisfying performance of OER catalysts when integrated in real‐world devices. Herein, the OER active sites for three mainstream types of NPMCs including non‐precious transition metal oxides/(oxy)hydroxides, metal‐free carbon materials, and hybrid non‐precious metal and carbon composites are reviewed. In addition, possible degradation mechanisms for active sites and mitigation strategies are discussed in detail. This review also provides insights into the gaps between R&D of NPMCs for the OER and their applications in practical devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • The TMSCH-derived CEI/SEI films effectively protect NCM811 cathode and Li anode. • The detrimental effects of HF are alleviated by Si-O functional group of TMSCH. • The cyclic performance of the Li/NCM811 cell with TMSCH is significantly enhanced. • The growth of Li dendrites is inhibited by the TMSCH-derived double-layer SEI film. Li metal batteries (LMBs) coupled with Ni-rich materials are promising candidates for next-generation high-energy-density lithium batteries. However, due to the inferior stability of cathode/solid-electrolyte interphases (CEI/SEI) and aggressive chemistry of Ni-rich cathode materials, Li metal anode (LMA) and LiPF 6 -based carbonate electrolytes pose a threat to the achievement of high-energy-density LMBs. Herein, 1-(trimethylsilyloxy)cyclohexene (TMSCH) with functional groups (C=C, Si-O) as a novel multi-functional electrolyte additive is employed to regular the CEI/SEI films on the both Ni-rich cathode materials (LiNi 0.8 Co 0.1 Mn 0.1 O 2 , NCM811) and LMA surface, and scavenge detrimental hydrogen fluoride (HF) to enhance electrochemical performances of the Li/NCM811 batteries. Furthermore, the theoretical calculation, electrochemical measurements and physical characterizations demonstrate the feasibility and effectiveness of the strategy. Specially, the TMSCH-derived SEI film exhibits a hierarchical structure consisting of an organic-rich outer layer and a LiF-rich inner layer. Accordingly, the microcracks generation of NCM811 secondary particles, transition metal ions dissolution, lithium dendrite growth, parasitic reactions and HF generation of electrolyte are effectively addressed. As a result, with existence of the TMSCH additive, the capacity retention of Li/NCM811 batteries at 1C are remarkably enhanced from 68.2% to 84.9% at 30 °C and 64.2% to 85.8% at 45 °C. Furthermore, the Li/Li symmetric cells with TMSCH can stably cycle over 1000 h at 0.2 mA cm−2 and exhibit super-low overpotential of 75 mV at 1 mA cm−2. [ABSTRACT FROM AUTHOR]

Fabricating active materials into specific macrostructures is critical in the pursuit of high electro-catalytic activity. Herein we demonstrate that a three-dimensional (3D) architecture of NiFe layered double hydroxide (NiFe-LDH) significantly reduced the onset potential, yielded high current density at small overpotentials, and showed outstanding stability in electrochemical oxygen evolution reaction. [ABSTRACT FROM AUTHOR]