Electrocatalytic nitrogen reduction (NRR) is regarded as an energy-efficient technology to produce NH 3 . Nevertheless, achieving high NH 3 yield and Faradaic efficiency (FE) under ambient conditions remains a great challenge. Herein, 1T/2H mixed-phase MoS 0·5 Se 1.5 (named 1T/2H MoSSe) nanoflower, as an efficient non-noble metal NRR electrocatalyst, was synthesized by the one-step solvothermal method. 1T/2H MoSSe realizes an excellent NH 3 yield of 32.32 μg h −1 mg cat. −1 at −0.45 V vs. RHE and an outstanding FE of 12.66% at −0.40 V vs. RHE in 0.1 M HCl, which are better than pure MoS 2 (NH 3 yield: 15.16 μg h −1 mg cat. −1 , FE: 0.35%) and MoSe 2 (NH 3 yield: 26.42 μg h −1 mg cat. −1 , FE: 2.75%). Density functional theory (DFT) calculations exhibit that MoSSe catalyst is structurally favorable to the potential-determining step (PDS, *NH–NH 2 → *NH 2 –NH 2 ) and thus shows increased NRR activity and selectivity. A promising tactic for the rational design of economical, efficient, and durable NRR electrocatalysts is proposed in this work.
Featuring intrinsic out-of-plane dipoles and broken inversion symmetry, Janus transition metal dichalcogenides (TMDs) provide a unique platform for exploring nonlinear twistronics at the two-dimensional limit. However, how the macroscopic nonlinear polarization is governed by hierarchical modulation, where the atomic interfacial configuration acts as the primary structural switch and the twist angle provides secondary phase tuning, remains experimentally unresolved in polar Janus homostructures. Here, we construct Janus MoSSe artificial homostructures with precise angular control using a pristine transfer technique and systematically elucidate their coherent superposition mechanisms in nonlinear optical processes via polarization-resolved SHG spectroscopy. We show that in conventional MoSSe/SSeMo bilayers with an S–Se van der Waals interface the SHG response strictly follows a symmetry-governed vector superposition principle, enabling continuous modulation from constructive to destructive contributions through twist-angle tuning. More importantly, in anomalous MoSSe/SeSMo bilayers featuring a Se–Se interface with antiparallel out-of-plane dipole alignment, the SHG signal is profoundly suppressed. This pronounced quenching originates from the restoration of inversion symmetry in the Se–Se stacked configuration, which enforces the cancellation of second-order nonlinear polarizations within the electric-dipole approximation. These results demonstrate an effective hierarchical modulation of the nonlinear optical response in Janus materials enabled by interface engineering (Se–Se vs Se–S stacking) and angular control. More broadly, this work elucidates the physical origin of interlayer nonlinear optical interference in polar van der Waals systems and establishes Janus MoSSe homostructures as a versatile platform for tunable nonlinear photonics governed by dual degrees of freedom: twist angle and interfacial configuration.
Wanjin Huang,Shufei Tang,Wei Xiao,Yafei Chen,Lijun Li,Jianping Li
A reduced graphene oxide/molybdenum selenosulfide (rGO/MoSSe) heterojunction was synthesized, and a molecularly imprinted photoelectrochemical sensor for the detection of chlortetracycline was prepared. MoSSe was grown in situ on rGO by a hydrothermal method to form an rGO/MoSSe heterojunction, which acts as the sensitive film of the sensor. Since rGO can promote electron transfer and effectively inhibit electron–hole recombination, it effectively reduces the recombination probability of electrons and holes and improves the photoelectric efficiency, thus enhancing the detection sensitivity of the PEC sensor. The rGO/MoSSe was immobilized on an FTO electrode, and molecularly imprinted polymers (MIPs) were prepared by electropolymerization on the rGO/MoSSe-modified FTO electrode with chlortetracycline as the template molecule and o-phenylenediamine as the functional monomer, so as to construct a molecularly imprinted photoelectrochemical (MIP-PEC) sensor. The determination of chlortetracycline was realized by the strategy of a “gate-controlled effect”, and the detection range of the chlortetracycline concentration was 5.0 × 10−13–5 × 10−9 mol L−1 with a detection limit of 1.57 × 10−13 mol L−1. The sensor has been applied to the determination of chlortetracycline in animal-derived food samples.
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