Multifunctional catalytic sites regulation of atomic-scale iridium on orthorhombic-CoSe_(2)for high efficiency dual-functional alkaline hydrogen evolution and organic degradation

The earth-abundant and high-performance catalysts are crucial for commercial implementation of hydrogen evolution reaction(HER).Herein,a multifunctional site strategy to construct excellent HER catalysts by incorporating iridium(Ir)ions on the atomic scale into orthorhombic-CoSe2(Ir-CoSe_(2))was reported.Outstanding hydrogen evolution activity in alkaline media such as a low overpotential of 48.7 mV at a current density of 10 mA cm^(-2)and better performance than commercial Pt/C catalysts at high current densities were found in the Ir-CoSe_(2) samples.In the experiments and theoretical calculations,it was revealed that Ir enabled CoSe_(2)to form multifunctional sites to synergistically catalyze alkaline HER by promoting the adsorption and dissociation of H_(2)O(Ir sites)and optimizing the binding energy for H^(*)on Co sites.It was noticeable that the electrolytic system comprising the Ir-CoSe_(2)electrode not only produced hydrogen efficiently via HER,but also degraded organic pollutants(Methylene blue).The cell voltage of the dual-function electrolytic system was 1.58 V at the benchmark current density of 50 mA cm^(-2),which was significantly lower than the conventional water splitting voltage.It was indicated that this method was a novel strategy for designing advanced HER electrocatalysts by constructing multifunctional catalytic sites for hydrogen production and organic degradation.

Tailoring structural properties of carbon via implanting optimal co nanoparticles in n-rich carbon cages toward high-efficiency oxygen electrocatalysis for rechargeable zn-air batteries

Rational construction of carbon-based materials with high-efficiency bifunctionality and low cost as the substitute of precious metal catalyst shows a highly practical value for rechargeable Zn-air batteries(ZABs)yet it still remains challenging.Herein,this study employs a simple mixing-calcination strategy to fabricate a high-performance bifunctional composite catalyst composed of N-doped graphitic carbon encapsulating Co nanoparticles(Co@NrC).Benefiting from the core-shell architectural and compositional advantages of favorable electronic configuration,more exposed active sites,sufficient electric conductivity,rich defects,and excellent charge transport,the optimal Co@NrC hybrid(Co@NrC-0.3)presents outstanding catalytic activity and stability toward oxygen-related electrochemical reactions(oxygen reduction and evolution reactions,i.e.,ORR and OER),with a low potential gap of 0.766 V.Besides,the rechargeable liquid ZAB assembled with this hybrid electrocatalyst delivers a high peak power density of 168 mW cm^(−2),a small initial discharge-charge potential gap of 0.45 V at 10 mA cm^(−2),and a good rate performance.Furthermore,a relatively large power density of 108 mW cm^(−2) is also obtained with the Co@NrC-0.3-based flexible solid-state ZAB,which can well power LED lights.Such work offers insights in developing excellent bifunctional electrocatalysts for both OER and ORR and highlights their potential applications in metal-air batteries and other energy-conversion/storage devices.

Efficient ammonia production over e_(g)-occupancy-optimized perovskite electrocatalysts

Renewable-energy-driven nitrate(NO_(3)^(−))electroreduction to ammonia(NH_(3))(NERA)has been an attractive technology for decarbonizing NH_(3)production and wastewater treatment.Improving NERA efficiency requires electrocatalysts that are earth-abundant and show fantastic performance.Here we report a semiempirical activity descriptor of eg occupancy(of surface B-site cations)for identifying inexpensive perovskite oxides with extremely high efficacy toward NERA.We establish the descriptor by systematic investigations of more than 10 perovskite oxides.These investigations demonstrate that their intrinsic NERA activities display a volcano-shaped dependence on eg occupancy and the optimized intrinsic activities are accessible at near-1 eg occupancies.This could plausibly be attributed to the favorable overlaps between surface adsorbates and vertically-oriented eg orbitals.More importantly,utilizing this descriptor,we predict a highly active,selective,and durable NERA electrocatalyst with a composition of Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF).Because of its close-to-1 e_(g)occupancy(i.e.~1.2),the BSCF features a superior NH_(3)production rate of 0.12 g·h^(−1)·mg_(cat.)^(−1)(Faradaic efficiency of 97.8%)that is at top of the volcano plot,and substantially outperforms most NERA electrocatalysts reported in literature.

A drug-loaded composite coating to improve osteogenic and antibacterial properties of Zn-1Mg porous scaffolds as biodegradable bone implants

Zinc(Zn)alloy porous scaffolds produced by additive manufacturing own customizable structures and biodegradable functions,having a great application potential for repairing bone defect.In this work,a hydroxyapatite(HA)/polydopamine(PDA)composite coating was constructed on the surface of Zn-1Mg porous scaffolds fabricated by laser powder bed fusion,and was loaded with a bioactive factor BMP2 and an antibacterial drug vancomycin.The microstructure,degradation behavior,biocompatibility,antibacterial performance and osteogenic activities were systematically investigated.Compared with as-built Zn-1Mg scaffolds,the rapid increase of Zn2+,which resulted to the deteriorated cell viability and osteogenic differentiation,was inhibited due to the physical barrier of the composite coating.In vitro cellular and bacterial assay indicated that the loaded BMP2 and vancomycin considerably enhanced the cytocompatibility and antibacterial performance.Significantly improved osteogenic and antibacterial functions were also observed according to in vivo implantation in the lateral femoral condyle of rats.The design,influence and mechanism of the composite coating were discussed accordingly.It was concluded that the additively manufactured Zn-1Mg porous scaffolds together with the composite coating could modulate biodegradable performance and contribute to effective promotion of bone recovery and antibacterial function.