Abstract
Transition metal dichalcogenide materials have been explored extensively as catalysts to negotiate the hydrogen evolution reaction, but they often run at a large excess thermodynamic cost. Although activating strategies, such as defects and composition engineering, have led to remarkable activity gains, there remains the requirement for better performance that aims for real device applications. We report here a phosphorus-doping-induced phase transition from cubic to orthorhombic phases in CoSe2. It has been found that the achieved orthorhombic CoSe2 with appropriate phosphorus dopant (8 wt%) needs the lowest overpotential of 104 mV at 10 mA cm−2 in 1 M KOH, with onset potential as small as −31 mV. This catalyst demonstrates negligible activity decay after 20 h of operation. The striking catalysis performance can be attributed to the favorable electronic structure and local coordination environment created by this doping-induced structural phase transition strategy.
Highlights
Transition metal dichalcogenide materials have been explored extensively as catalysts to negotiate the hydrogen evolution reaction, but they often run at a large excess thermodynamic cost
We achieved marcasite-type o-CoSe2|P by annealing assynthesized c-CoSe2 nanobelts[27] (Supplementary Fig. 1) with NaH2PO2·H2O under an argon atmosphere, which was decomposed to PH3 species in situ that enable the P-doping and phase transition (Fig. 1a and Methods)
Selected-area electron diffraction (SAED) patterns show stretched, single-crystal-like diffraction spots that are readily distinguishable from the original pattern of c-CoSe2, resulting from the porous orthorhombic structures
Summary
Transition metal dichalcogenide materials have been explored extensively as catalysts to negotiate the hydrogen evolution reaction, but they often run at a large excess thermodynamic cost. Recent advances in the search of new HER catalysts have shown that a range of transition metal dichalcogenides (TMD), such as MoS24–9, MoSe210, WS211, TaS212, FeS213, CoS214, CoSe215–17, and CoTe218 are attractive alternatives Of these TMD catalysts, the intrinsic active site of MoS2 was well identified[19], which stimulated strategies to tailor MoS2 for promoted HER electrocatalysis through modulating material parameters such as defects[5], van der Waals interactions[6], morphology[7], composition[8], and crystal phases[9]. As with MoS2 and WS2, structural phase transition from the 2H (trigonal prismatic) to 1T (octahedral) phase can be induced through chemical exfoliation of their layered compounds[11,20], which leads to enhanced HER activities owing to the strained metallic 1T phase Another layered TMD material, CoSe2, has recently been investigated as promising catalyst for H2 production from water[15,16,21]. Our findings raise the possibility in accessing advanced electrocatalysts through element-doping-induced structural phase transition
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