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Herein, we report an effective approach to electricity storage in biofuels by selective electrocatalytic reduction of levulinic acid (LA) to high-energy-density valeric acid (VA) or γ-valerolactone (gVL) on a non-precious Pb electrode in a single-polymer electrolyte membrane electrocatalytic (flow) cell reactor with a very high yield of VA (>90 %), a high Faradaic efficiency (>86 %), promising electricity storage efficiency (70.8 %), and a low electricity consumption (1.5 kWhL(VA)(-1) ). The applied potential and electrolyte pH can be used to accurately control the reduction products: lower overpotentials favor the production of gVL, whereas higher overpotentials facilitate the formation of VA. A selectivity of 95 % to VA in acidic electrolyte (pH 0) and 100 % selectivity to gVL in neutral electrolyte (pH 7.5) are obtained. The effect of the molecular structure on the electrocatalytic reduction of ketone and aldehyde groups of biomass compounds was investigated. Whereas LA can be fully electroreduced to VA though a four-electron transfer, the C-O groups are only electroreduced to -OH by a two-electron-transfer process when glyoxylic acid and pyruvic acid serve as feedstocks.

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Novel PdFe-nanoleaves (NLs) have been prepared through a wet chemistry-based solution phase reduction synthesis route. High-resolution transmission electron microscopy (HR-TEM) and scanning transmission electron microscopy (S/TEM) coupled with high-spatial-resolution compositional analysis clearly show that this newly developed structure is assembled from Pd-rich nanowires (Pd-NWs) surrounded by Fe-rich sheets. The Pd-NWs have diameters in the range of 1.8-2.3 nm and large electrochemical surface areas of >50 m 2 /g. Their length (30-100 nm) and morphology can be tuned by altering the nanostructure synthesis conditions and the Fe amount in the NLs. With increasing Fe content, thinner and longer sheet-enveloped nanowires can be prepared. The side surfaces of PdNWs observed by HR-TEM are predominantly Pd(111) facets, while the tips and ends are Pd(110) and Pd(100) facets. By etching away the enveloping Fe-rich sheets using an organic acid, the Pd-rich NWs are exposed on the surfaces of the nanoleaves, and they demonstrate high reactivity toward electrocatalytic reduction of oxygen in a 0.1 M NaOH electrolyte, i.e., a factor of 3.0 increase in the specific activity and a factor of 2.7 increase in the mass activity, compared to a commercial Pt/C catalyst (at 0 V vs. Hg/HgO). The electrocatalytic activity enhancement can be attributed to the unique nanoleave structure, which provides more Pd(111) facets, a large surface area, and more resistance to Pd oxide formation. ' INTRODUCTIONWithout the Carnot cycle limitation, low-temperature proton exchange membrane fuel cells (PEMFCs) directly convert the chemical energy of fuels into electricity with high theoretical efficiency (i.e., 83% for H 2 fuel at a thermodynamic potential of 1.229 V under standard conditions) and zero emission; therefore, they are considered to be a promising sustainable power source. 1 However, the sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode remains a great scientific challenge that hinders the high energy conversion efficiency of PEMFCs. 2 Platinum group metal (PGM)-based electrocatalysts are currently used for PEMFCs to reduce the large ORR overpotential. 2c-e Unfortunately, even on the most active Pt surface, the overpotential is >250 mV at open circuit voltage (OCV). The thermodynamic efficiency drops from 83% (1.229 V) to, i.e., 66% at an OCV value of 0.98 V under standard conditions. 1a,2 Since the exchange current density of the ORR is very small (10 -9 A/cm 2 at the Pt surface), 2e to get a usable output current, the operating voltage must be largely reduced to, i.e., 0.65 V, making the energy efficiency of PEMFCs decrease further to 44%.PGM-based multimetallic nanostructures with well-controlled size, shape, structure, chemical composition, and morphology can effectively enhance the catalytic reaction kinetics through modifying surface compositions, optimizing highly active crystalline facets, and tuning electronic structures. 3 Wet-chemical synthesis (WCS) approaches have emerged as one of the most promising me...