Optimizing the Atom Substitution of Er in WS₂ Nanosheets for High-Performance Photoelectrochemical Applications

Abstract

Introducing the density of states or defects within the band gap in two-dimensional nanomaterials by rare-earth (RE) element substitution would make them potential candidates for application in next-generation optoelectronic devices. Furthermore, doping with RE elements possessing fine-structured spectral emission and absorption can improve the fundamental research and technological applications of two-dimensional nanomaterial-based photoelectrochemical (PEC) activity due to abundant active sites and low interfacial contact resistance with the electrolyte. Herein, an Er-doping strategy is utilized for the synthesis of Er-doped WS 2 nanosheets to simultaneously achieve both upconversion and downconversion emissions, which can efficiently absorb more solar light for PEC activity. We first report a two-step method combining magnetic sputtering and sulfurization to synthesize Er-doped WS 2 nanosheet-based electrodes. The effect of Er doping into a single-phase hexagonal-structured WS 2 (p-type semiconductor)based electrode on PEC activity is investigated and compared with pristine WS 2 counterparts under one standard sun condition. Results indicate that a photocurrent density of −20 μA•cm −2 at −0.21 V versus RHE (reversible hydrogen electrode) with an enhancement factor of ∼200-fold due to a wider absorbance range (400−808 nm) and a decreased overpotential for hydrogen reduction are achieved. Moreover, the resistance of the Er-doped WS 2 electrode is found to be decreased from 500 to 28 kΩ, with nearly a 20-fold decrease compared with that of the pristine WS 2 counterparts, contributing to the higher efficiency in electron transfer into the electrolyte. The mechanism is confirmed by Monte Carlo simulations and first-principles calculations. The Er-doped WS 2 nanosheets are therefore a promising substitute for noble metals in PEC applications.

Enhanced Visible-Light Response of Ultrathin Er-Doped MoS2 Nanosheets through a Wet-Chemical Method

“…Meanwhile, the ability to capture photons of Er 3+ leads to stronger light absorption and utilization capacity (Figure S9). The energy transformation from Er 3+ to S defects in the MoS 2 host will induce the generation of electron–hole pairs, which can enhance the visible-light photoresponse of MoS 2 :Er.…”

Chemical Vapor Deposition of Er-Doped WS2 Flakes with Near-Infrared Emission and Enhanced Near-Infrared Photoresponse

“…The photoresponse of pure WS 2 under 808 nm laser excitation can be attributed to the generation of nonequilibrium carriers induced by the defect-related traps. , The increased I ph of the WE-based device can be attributed to the selective trapping of Er 3+ ions for 808 nm photons, and the promoting effect of impurity ion energy levels (around the Fermi level) on the separation of electron–hole pairs . Er 3+ ions can absorb 808 nm photons, and then transfer energy to the host, resulting in photogenerated electron–hole pairs . Meanwhile, the relatively longer relaxation time of the photocurrent in the WE-based (10.58 ms) device compared to that of the WS 2 -based one (1.57 ms) demonstrates the trapping effect caused by Er dopants (Figure S11).…”

“…Among them, the CVD method offers the advantage of large-area and high-quality 2D TMDs. , The introduction and dosage of dopants are the key factors that influence the growth of chemically produced films. , However, how Ln-doping affects the growth and optical characteristics of 2D TMDs is still under investigation. Meanwhile, previous studies have demonstrated that Er 3+ doping can significantly enhance the photoresponse of WS 2 films in the visible region. , Given the significance of the NIR band for optical communication, it will be significant to systematically investigate the effects of Er 3+ on the NIR photoresponse of 2D WS 2 .…”

“…Meanwhile, previous studies have demonstrated that Er 3+ doping can significantly enhance the photoresponse of WS 2 films in the visible region. 19,22 Given the significance of the NIR band for optical communication, it will be significant to systematically investigate the effects of Er 3+ on the NIR photoresponse of 2D WS 2 .…”

Microstructure, grain and nanowire growth during selective laser melting of Ag–Cu/diamond composites

“…The addition of nano/micronsized diamond particles can customise Ag's coefficient of thermal expansion and enhance its corrosion resistance, mechanical properties, and thermal conductivity properties. This kind of MMCs is promising to revolutionise photodetections, 11,12 thermal convection reuse, 13 and imaging sensor industries. 14 To date, MMCs are primarily manufactured by solid-state processing (i.e.…”