Electrocatalytic biomass valorization with renewable energy input represents a promising way to produce sustainable and nonfossil-based carbon products. Even more desirable is that the oxidative biomass upgrading can be integrated with H 2 production in a single electrolyzer. Herein, we report that electrodeposited Co−P can act as competent electrocatalysts for 5-hydroxymethylfurfural (HMF) oxidation to 2,5-furandicarboxylic acid (FDCA) at the anode and H 2 production at the cathode simultaneously in alkaline media. When serving as a catalyst precursor on the anode, Co−P was able to achieve a current density of 20 mA/cm 2 for HMF oxidation in 1.0 M KOH with 50 mM HMF at 1.38 V vs RHE, prior to the takeoff of the competing reaction, O 2 evolution. Long-term chronoamperometry demonstrated a nearly 100% conversation of HMF and a ∼90% yield of FDCA. When HMF oxidation and H 2 evolution were integrated in one electrolyzer with a Co−P/Co−P catalyst couple, the potential required to achieve a current density of 20 mA/cm 2 was 1.44 V, 150 mV lower than that of overall water splitting. Nearly unity Faradaic efficiency was obtained for H 2 evolution. Overall, our results indicate that it is feasible to employ earth-abundant electrocatalyts to integrate H 2 production and oxidative biomass upgrading with higher energy conversion efficiency than water splitting as well as to produce valuable products at both cathode and anode in a single electrolyzer.

No abstract

Light-addressable electrochemical sensors (LAESs) are a class of sensors that use light to activate an electrochemical reaction on the surface of a semiconducting photoelectrode. Here, we investigate semiconductor/metal (Schottky) junctions formed between n-type Si and Au nanoparticles as light-addressable electrochemical sensors. To demonstrate this concept, we prepared n-Si/Au nanoparticle Schottky junctions by electrodeposition and characterized them using scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. We found that the sensors behaved almost identically to Au disk electrodes for the oxidation of an outer-sphere redox couple (ferrocene methanol) and two inner-sphere redox couples (potassium ferrocyanide and dopamine). In buffered dopamine solutions, we observed broad linear ranges and submicromolar detection limits. We then used local illumination to generate a virtual array of electrochemical sensors for dopamine as a strategy for circumventing sensor fouling, which is a persistent problem for electrochemical dopamine sensors. By locally illuminating a small portion of the photoelectrode, many measurements of fouling analytes can be made on a single sensor with a single electrical connection by moving the light beam to a fresh area of the sensor. Altogether, these results pave the way for Schottky junction light-addressable electrochemical sensors to be useful for a number of interesting future applications in chemical and biological sensing.

Here we investigate the use of 3D printed graphene/poly(lactic acid) (PLA) electrodes for quantifying trace amounts of Hg, Pb, and Cd. We prepared cylindrical electrodes by sealing a 600 μm diameter graphene/PLA filament in a pipette tip filled with epoxy. We characterized the electrodes using scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry in ferrocene methanol. The physical characterization showed a significant amount of disorder in the carbon structure and the electrochemical characterization showed quasi‐reversible behavior without any electrode pretreatment. We then used unmodified graphene/PLA electrode to quantify Hg, and Pb and Cd in 0.01 M HCl and 0.1 M acetate buffer using square wave anodic stripping voltammetry. We were able to quantify Hg with a limit of detection (LOD) of 6.1 nM (1.2 ppb), but Pb and Cd did not present measurable peaks at concentrations below ∼400 nM. We improved the LODs for Pb and Cd by depositing Bi microparticles on the graphene/PLA and, after optimization, achieved clear stripping peaks at the 20 nM level for both ions (4.1 and 2.2 ppb for Pb2+ and Cd2+, respectively). The results obtained for all three metals allowed quantification below the US Environmental Protection Agency action limits in drinking water.

Rotating ring disk electrodes (RRDEs) are a powerful and versatile tool for mechanistically investigating electrochemical reactions at electrode surfaces, particularly in the area of electroanalysis and catalysis. Despite their importance, only limited electrode materials (typically glassy carbon, platinum, and gold) and combinations thereof are available commercially. In this work, we present a method employing three-dimensional (3D) printing in conjunction with machined brass components to produce housing, which can accommodate any electrode material in, e.g ., pressed powdered pellet, wafer, rod, foil, or vapor deposited onto a conductive substrate form. In this way, the range and usability of RRDEs is extended. This custom do-it-yourself (DIY) approach to fabricating RRDEs also enables RRDEs to be produced at a significant fraction of the cost of commercial RRDEs. To illustrate the versatility of our approach, coplanar boron-doped diamond (BDD) RRDEs are fabricated for the first time using the approach described. Experimental collection efficiencies for the redox couple FcTMA + /FcTMA 2+ are found to be very close to those predicted theoretically. BDD electrodes serve as an ideal electrocatalyst support due to their low background currents, wide solvent potential window in aqueous solution, and chemical and electrochemical stability in acid and alkali solutions. The BDD RRDE configuration is employed to investigate the importance of surface-incorporated nondiamond carbon in BDD on hydrogen peroxide generation via the oxygen reduction reaction in acid solutions.

Electrochemical ozone production (EOP) from water is an attractive, green technology for disinfection. Boron doped diamond (BDD) electrodes, grown by chemical vapor deposition (CVD), have been widely adopted for EOP due to their wide anodic window in water and excellent chemical and electrochemical stability. High pressure high temperature (HPHT) synthesis, an alternative growth technique used predominantly for the high-volume synthesis of nitrogen doped diamond microparticles, has been seldom employed for the production of conductive BDD electrodes. In this letter, we demonstrate, for the first time, the use of BDD electrodes fabricated from HPHT conductive BDD microparticles for EOP. The BDD microparticles are first compacted to produce freestanding solid electrodes and then laser micromachined to produce a perforated electrode. The compacted HPHT BDD microparticle electrodes are shown to exhibit high EOP, producing 2.23 ± 0.07 mg L-1 of ozone per ampere of current, at consistent levels for a continuous 20 hr period with no drop off in performance. The HPHT electrodes also achieve a reasonable current efficiency of 23%, at a current density of 770 mA cm-2.

Rotating ring disk electrodes (RRDEs) are a powerful and versatile tool for mechanistically investigating electrochemical reactions at electrode surfaces, particularly in the area of electroanalysis and catalysis. Despite their importance only limited electrode materials (typically glassy carbon, platinum and gold) and combinations thereof are available commercially. In this work we present a method employing 3D printing in conjunction with machined brass components to produce housing which can accommodate any electrode material in e.g. pressed powdered pellet, wafer, rod, foil or vapor deposited onto a conductive substrate, form. In this way the range and usability of RRDEs is extended. This custom DIY approach to producing RRDEs, also enables RRDEs to be produced at a significant fraction of the cost of commercial RRDEs. To illustrate the versatility of our approach, co-planar boron doped diamond (BDD) RRDEs are fabricated for the first time, using the approach described. Experimental collection efficiencies for the redox couple FcTMA+/FcTMA2+ are found to be very close to those predicted theoretically. BDD electrodes serve as an ideal electrocatalyst support due to their low background currents, wide solvent window in aqueous solution and chemical and electrochemical stability in acid and alkali solutions. The BDD RRDE configuration is employed to investigate the importance of surface incorporated non-diamond carbon in BDD on hydrogen peroxide generation via the oxygen reduction reaction in acid solutions.

This paper presents a micromachined thermal reactor. Silicon substrate remains unheated because of thermal isolation design, during thermal cycling of the reaction chamber. Employed side-heating concept has significantly improved in-chamber temperature uniformity. Finite-element-analysis is carried out to optimise the thermal performance. Experimental results have proved that the thermal reactor can easily be integrated with other non-thermal components. Integration of the device with other components or modules of miniaturised total analysis systems (pTAS) is very promising .