Regulating Water Reduction Kinetics on MoP Electrocatalysts Through Se Doping for Accelerated Alkaline Hydrogen Production

Owing to its low cost, high conductivity, and chemical stability, Molybdenum phosphide (MoP) has great potential for electrochemically catalyzing the hydrogen evolution reaction (HER). Unfortunately, the development of high-activity MoP still remains a grand challenge in alkali-electrolyzers due to its sluggish water reduction kinetics. Here, we demonstrate a novel strategy for regulating the HER kinetics of the MoP nanowire cathode through partially substituting P atoms with Se dopants. In alkaline solutions, the Se-doped MoP (Se-MoP) nanowire cathode exhibits excellent HER performance with a greatly-decreased overpotential of ∼61 mV at 10 mA cm−2 and a Tafel slope of ∼63 mV dec−1, outperforming currently reported MoP-based electrocatalysts. Experimental and theoretical investigations reveal that Se doping not only facilitates the water dissociation on MoP, but also optimize the hydrogen adsorption free energy, eventually speeding up the sluggish alkaline HER kinetics. Therefore, this work paves a new path for designing MoP-based electrocatalyst with high HER performance in alkaline electrolyzers.

Using Cu–Zn–Sn–O Precursor to Optimize CZTSSe Thin Films Fabricated by Se Doping With CZTS Thin Films

The copper–zinc–tin oxide (CZTO) precursor was synthesized to avoid sudden volume expansion from CZTO precursor to Cu2ZnSnS4 (CZTS) thin films and smooth CZTSSe thin-film surfaces without pinholes. The CZTO precursor was prepared by coprecipitation and ball milling to form nanoink of CZTO. Based on the CZTO precursor, the CZTS thin film was fabricated and then selenized to make pinhole-free and flat Cu2ZnSn(S,Se)4(CZTSSe) thin films. The results show that the CZTO precursor greatly contributed to elevating the homologous surface characteristics and crystallinity of CZTSSe thin films by controlling selenium temperature, selenium time, and selenium source temperature. Finally, the conversion efficiency of the CZTSSe thin-film solar cell fabricated from the CZTO precursor was 4.11%, with an open-circuit voltage (Voc) of 623 mV, a short circuit current density (Jsc) of 16.02 mA cm−2, and a fill factor (FF) of 41.2%.

Anomalous Thermopower and High ZT in GeMnTe2 Driven by Spin’s Thermodynamic Entropy

NaxCoO2 was known 20 years ago as a unique example in which spin entropy dominates the thermoelectric behavior. Hitherto, however, little has been learned about how to manipulate the spin degree of freedom in thermoelectrics. Here, we report the enhanced thermoelectric performance of GeMnTe2 by controlling the spin’s thermodynamic entropy. The anomalously large thermopower of GeMnTe2 is demonstrated to originate from the disordering of spin orientation under finite temperature. Based on the careful analysis of Heisenberg model, it is indicated that the spin-system entropy can be tuned by modifying the hybridization between Te-p and Mn-d orbitals. As a consequent strategy, Se doping enlarges the thermopower effectively, while neither carrier concentration nor band gap is affected. The measurement of magnetic susceptibility provides a solid evidence for the inherent relationship between the spin’s thermodynamic entropy and thermopower. By further introducing Bi doing, the maximum ZT in Ge0.94Bi0.06MnTe1.94Se0.06 reaches 1.4 at 840 K, which is 45% higher than the previous report of Bi-doped GeMnTe2. This work reveals the high thermoelectric performance of GeMnTe2 and also provides an insightful understanding of the spin degree of freedom in thermoelectrics.

Istraživanje i dokazivanje dopinga kao sportskog delikta s osvrtom na kaznenopravni aspekt

O dopingu kao kažnjivoj radnji postoje različita teorijska stajališta i mišljenja. Jedni smatraju da se doping treba kažnjavati kaznenopravnim sankcijama, drugi da je dovoljna prekršajnopravna, a treći stegovna sankcija, kako bi se postigla svrha kažnjavanja. U našem pravnom sustavu borba protiv dopinga evoluirala je tako da danas imamo samodoping kao stegovno djelo koje se kažnjava prema pravilima proisteklima iz Svjetskog antidoping kodeksa. S druge strane, zakonodavac propisuje neovlaštenu proizvodnju i promet tvari zabranjenih u sportu kao zasebno kazneno djelo delicta communia, za koje se kažnjava, inter alia, onaj koji omogućava i stavlja na raspolaganje zabranjene tvari sportašu ili koji drugoga navodi na trošenje tih tvari, a to može biti i sam sportaš. Međutim, borba protiv dopinga ne uključuje samo materijalnopravno normiranje nego, štoviše, pitanja načina dokazivanja, otkrivanja i procesuiranja mogućih počinitelja. Stoga autori u ovom radu iznose procesnopravne odredbe kojima je regulirana borba protiv dopinga, što ukazuje na distinkcije koje postoje u pogledu pojedinih počinitelja ovog kaznenog/stegovnog djela. Doping je opasnost modernog svijeta koji se sastoji u prijevarnom postupanju počinitelja uzimanjem zabranjenih tvari radi postizanja vrhunskih rezultata. Pored toga što je nespojiv s etičkim načelima sporta, te što se uzimanjem dopinga može narušiti zdravlje sportaša, doping predstavlja delikt koji je potrebno sankcionirati. Pri tome, ostvariti punitivnu svrhu a ne utjecati negativno na ugled sporta, izazov je koji je stavljen i pred zakonodavca i pred sustav sporta općenito. Stoga borba protiv dopinga mora obuhvaćati sustavnu koordinaciju materijalnopravnih i postupovnih odredbi u cilju zaštite integriteta čistog sporta.

First Principles Study in the Electronic Structures and Optical Properties of Chalcogenide-doped AgInS2

The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) is adopted to simulate the electronic structures and optical properties of AgInS2 semiconductors with S substitution by chalcogenides. The chalcogenide-doped AgInS2 semiconductor can be synthesized at the normal conditions due to the formation energies. O and Se doping in AgInS2 remain the semiconductor with the narrow band gaps, while Te doping converts semiconductor to metal. In the presence of the impurities, the contributions from p states of chalcogenides are involved, accountable for the reduction of the band gaps. Using the reflectivity and absorption coefficients, the optical properties with extensive absorption range and low reflectivity are attained by incorporating AgInS2 semiconductors with chalcogenides. Finally, this theoretical work launches a broader understanding of the absorber materials and also predicts the natural properties as the alternative for the solar cell applications.