Crystalline 2D hexagonal boron nitride (2D-hBN) nanosheets are explored as a potential electrocatalyst toward the electroanalytical sensing of dopamine (DA). The 2D-hBN nanosheets are electrically wired via a drop-casting modification process onto a range of commercially available carbon supporting electrodes, including glassy carbon (GC), boron-doped diamond (BDD), and screen-printed graphitic electrodes (SPEs). 2D-hBN has not previously been explored toward the electrochemical detection/electrochemical sensing of DA. We critically evaluate the potential electrocatalytic performance of 2D-hBN modified electrodes, the effect of supporting carbon electrode platforms, and the effect of "mass coverage" (which is commonly neglected in the 2D material literature) toward the detection of DA. The response of 2D-hBN modified electrodes is found to be largely dependent upon the interaction between 2D-hBN and the underlying supporting electrode material. For example, in the case of SPEs, modification with 2D-hBN (324 ng) improves the electrochemical response, decreasing the electrochemical oxidation potential of DA by ∼90 mV compared to an unmodified SPE. Conversely, modification of a GC electrode with 2D-hBN (324 ng) resulted in an increased oxidation potential of DA by ∼80 mV when compared to the unmodified electrode. We explore the underlying mechanisms of the aforementioned examples and infer that electrode surface interactions and roughness factors are critical considerations. 2D-hBN is utilized toward the sensing of DA in the presence of the common interferents ascorbic acid (AA) and uric acid (UA). 2D-hBN is found to be an effective electrocatalyst in the simultaneous detection of DA and UA at both pH 5.0 and 7.4. The peak separations/resolution between DA and UA increases by ∼70 and 50 mV (at pH 5.0 and 7.4, respectively, when utilizing 108 ng of 2D-hBN) compared to unmodified SPEs, with a particularly favorable response evident in pH 5.0, giving rise to a significant increase in the peak current of DA. The limit of detection (3σ) is found to correspond to 0.65 μM for DA in the presence of UA. However, it is not possible to deconvolute the simultaneous detection of DA and AA. The observed electrocatalytic effect at 2D-hBN has not previously been reported in the literature when supported upon carbon or any other electrode. We provide valuable insights into the modifier-substrate interactions of this material, essential for those designing, fabricating, and consequently performing electrochemical experiments utilizing 2D-hBN and related 2D materials.

[a] 1IntroductionAs the availability of naturale nergy resources depletes,i t has become increasingly important to finda lternative means of energyp roduction [1].T he most common alternativest of ossil fuels are renewable sources such as hydroelectric power and wind turbines,a nd for transportation purposes,e lectrolysers for fuel cells.T he latteri sa n electrochemical device that relies on the oxidation of af uel, such as methanol, at aw orking electrode (anode), while the protons liberated act as ar educinga gent to oxygen in the cathodicp art of the fuel cell. Research into proton exchange membrane (PEM) fuel cells,i nw hich the oxygen reduction reaction( ORR) occurs,i sd irected towardsi mproving power output, efficiency,a nd longevity,s uch that devices become viable for the transportation fuel cell market [ 2].TheO RR occurs at the cathode of PEM fuel cells and has proved to be problematic (dependent upon the catalyst utilised), primarily limiting the lifetimes of devices due to electrode fouling [3,4].F or example,P EM fuel cell degradation [2] is synonymous with the ORR due to the formationo fh ydrogen peroxide (H 2 O 2 )w hen using catalysts that reduce oxygen via at wo electron pathway [5].F urthermore, slow electront ransfer kinetics during the ORR can potentially result in a5 0% voltage loss and reduce the performance of aP EM fuel cell [2,6].T here Abstract:C rystalline2 Dh exagonal Boron Nitride( 2D-hBN) is explored as ap otential electrocatalyst towards the oxygen reduction reaction (ORR) when electrically wired via ad rop-casting approach upon ar ange of carbon based electrode surfaces;n amely,g lassy carbon (GC), boron-dopedd iamond (BDD), and screen-printed graphitic electrodes (SPEs). We consider the ORR in acidic conditions and critically evaluate the performanceo fu nmodified and 2D-hBN modified electrodes,i mplementing coverage studies (commonly neglected in the literature) in order to ascertain the true impact of this novel nanomaterial. Theb ehaviouro f2 D-hBN towards the ORR is shown to be highly dependent upon both the underlying carbon substrate and the coverage/mass utilised.2 D-hBN modified SPEs are foundt oexhibit the most beneficial response towards the ORR, reducingt he peak potential by ca. 0.28 Vw hen compared to an unmodified/bare SPE. Such improvements at this supporting substrate are inferred due to favourable 2D-hBNi nteraction with ridged surfaces exposing ah igh proportion of edge regions/sites, where conversely,w es how that relatively smooth substrate surfaces (such as GC) are less conducivet owards successful 2D-hBN immobilisation.I nt his paper, we reveal for the first time (in the specific caseo fu sing ar ough supporting substrate) that 2D-hBN gives riset o beneficial electrochemical behaviourt owards the ORR. Unfortunately,t his material is not considered an electrocatalyst for use within fuel cells given that the estimated number of electrons transferred during the ORRr anges between 1.90-2.45 for different coverages,i ndicatingt hat the ORR at 2D-hBN predomi...

Surfactant-exfoliated 2D hexagonal boron nitride (2D-hBN) nanosheets are fabricated using the surfactant sodium cholate in aqueous media and are explored towards the electrochemical reduction of oxygen.

Surfactant exfoliated 2D hexagonal Boron Nitride (2D-hBN) nanosheets are explored as a potential electrochemical sensing platform and evaluated towards the electroanalytical sensing of dopamine (DA) in the presence of the common interferents, ascorbic acid (AA) and uric acid (UA). Surfactant exfoliated 2D-hBN nanosheets (2-4 layers) fabricated using sodium cholate in aqueous media are electrically wired via a drop-casting modification process onto disposable screen-printed graphite electrodes (SPEs). We critically evaluate the performance of these 2D-hBN modified SPEs and demonstrate the effect of 'mass coverage' towards the detection of DA, AA and UA. Previous studies utilising surfactant-free (pristine) 2D-hBN modified SPEs have shown a beneficial effect towards the detection of DA, AA and UA when compared to the underlying/unmodified graphite-based electrode. We show that the fabrication route utilised to prepare 2D-hBN is a vital experimental consideration, such that the beneficial effect previously reported is considerably reduced when surfactant exfoliated 2D-hBN is utilised. We demonstrate for the first time, through implementation of control experiments in the form of surfactant modified graphite electrodes, that sodium cholate is a major contributing factor to the aforementioned detrimental behaviour. The significance here is not in the material per se, but the fundamental knowledge of the surfactant and surface coverage changing the electrochemical properties of the material under investigation. Given the wide variety of ionic and non-ionic surfactants that are utilised in the manufacture of novel 2D materials, the control experiments reported herein need to be performed in order to de-convolute the electrochemical response and effectively evaluate the 'underlying surface/surfactant/2D materials' electrocatalytic contribution.

A low-cost, scalable and reproducible approach for the mass production of screen-printed electrode (SPE) platforms that have varying percentage mass incorporations of 2D hexagonal boron nitride (2D-hBN) (2D-hBN/SPEs) is demonstrated herein. These novel 2D-hBN/SPEs are explored as a potential metal-free electrocatalysts towards oxygen reduction reactions (ORRs) within acidic media where their performance is evaluated. A 5% mass incorporation of 2D-hBN into the SPEs resulted in the most beneficial ORR catalysis, reducing the ORR onset potential by ca. 200 mV in comparison to bare/unmodified SPEs. Furthermore, an increase in the achievable current of 83% is also exhibited upon the utilisation of a 2D-hBN/SPE in comparison to its unmodified equivalent. The screen-printed fabrication approach replaces the less-reproducible and time-consuming drop-casting technique of 2D-hBN and provides an alternative approach for the large-scale manufacture of novel electrode platforms that can be utilised in a variety of applications.