Evaluating the Hydrogen Evolution Reaction Activity of Colloidally Prepared PtSe2 and PtTe2 Catalysts in an Alkaline Medium

The hydrogen evolution reaction (HER) in alkaline electrolytes using transition metal dichalcogenides is a research area that is not tapped into. Alkaline HER (2 H 2 O + 2 e - → H 2 + O H - ${{2H}_{2}O+2{e\ }^{-}\to {H}_{2}+{OH}^{-}{\rm \ }}$ ) is harder to achieve relative to acidic HER (H + + 2 e - → H 2 ${{H}^{+}+2{e\ }^{-}\to \ {H}_{2}}$ ), this is attributed to the additional water dissociation step that occurs in basic HER to generate H+ ions. In fact, for most catalysts, their HER activity decreases tremendously when the electrolyte is changed from acidic to basic conditions. Platinum dichalcogenides, PtX2 (X=S, Se, Te), are an interesting member of transition metal dichalcogenides (TMDs) as these show an immense hybridization of the Pt d orbitals and chalcogen p orbitals because of closely correlated orbital energies. The trend in electronic properties of these materials changes drastically as the chalcogen is changed, with PtS2 reported to exhibit semi-conductor properties, PtSe2 is semi-metallic or semi-conductive, depending on the number of layers, while PtTe2 is metallic. The effect of varying the chalcogen atom on the HER activity of Pt dichalcogenides will be studied. Pt dichalcogenides have previously been prepared by direct high-temperature chalcogen deposition of Pt substrate and evaluated as electrocatalysts for HER in H2SO4. The previously employed synthesis procedures for PtX2 limit these compounds' mass production and post-synthesis treatment. In this study, we demonstrated, for the first time the preparation of PtSe2 and PtTe2 by colloidal synthesis. Colloidal synthesis offers the possibility of large-scale synthesis of materials and affords the employment of the colloids at various concentrations in ink formulation. The electrochemical HER results acquired in 1 M KOH indicate that PtTe2 has a superior HER catalytic activity to PtSe2. A potential of 108 mV for PtTe2 and 161 mV for PtSe2 is required to produce a current density of -10 mA cm-2 from these catalysts. PtTe2 has a low Tafel slope of 79 mVdec-1, indicating faster HER kinetics on PtTe2. Nonetheless, the stability of these catalysts in an alkaline medium needs to be improved to render them excellent HER electrocatalysts.

Enhanced full-seawater splitting with a CoNiP@N,P-C core-shell electrocatalyst

This study investigated a novel electrocatalyst with a core-shell structure of CoNiP@N,P-C. The unique carbon shell of this catalyst serves a dual purpose: exposing numerous active sites and safeguarding CoNiP nanoparticles from dissolution caused by the electrolyte. As a result, the CoNiP@N,P-C nanoparticles exhibit exceptional electrochemical properties. The CoNiP@N,P-C catalyst displays overpotentials of 234 and 314 mV for the HER and OER, respectively, within a simulated seawater solution (1 M KOH + 0.5 M NaCl), indicating its outstanding catalytic performance. Moreover, when subjected to full seawater splitting, the CoNiP@N,P-C catalyst exhibited high activity, achieving a 1.71 V cell voltage at a current density of 10 mA cm-2. As revealed by density functional theory (DFT) calculations, the CoNiP@N,P-C catalyst exhibits Gibbs free energy for hydrogen adsorption (ΔGH* = -0.19 eV) that is decreased in comparison with CoP@N,P-C, NiP@N,P-C, and N,P-C (-0.321 eV, -0.434 eV, and 0.723 eV, respectively). This finding confirms that the core-shell structure plays a role in enhancing the HER kinetics and improving the catalytic performance, which is consistent with the experimental observations. Consequently, this study introduces the concept of utilizing bimetal phosphide core-shell structures for overall seawater splitting, offering a novel approach in this field of research.

Ru doping and interface engineering synergistically boost the electrocatalytic performance of a WP/WP2 nanosheet array for an efficient hydrogen evolution reaction

The surface electronic structure and morphology of catalysts have a crucial impact on the electrocatalytic hydrogen evolution reaction performance. This work reports on the fabrication of a Ru-doped WP/WP2 heterojunction nanosheet array electrode via a one-step phosphating treatment of a Ru-doped WO3 precursor. Benefitting from the large electrochemical active surface of nanosheet arrays, rich WP/WP2 heterojunction interface, and trace Ru atom doping, the catalyst has a fairly low overpotential of 58.0 mV at 10 mA cm-2 and a Tafel slope of 50.71 mV dec-1 in acid solution toward the electrocatalytic HER. Further, theoretical calculations unveil that Ru atom doping and interface effect synergistically optimized the electronic structure of the catalyst and hence weakened the adsorption capacity of the catalyst surface toward hydrogen (H), which lowered the Gibbs free energy (ΔGH*) and consequently effectively improved the HER performance. This work may open new avenues for developing advanced nanoarray electrodes with efficient electrochemical energy conversion.