The ability to synthesize compositionally complex nanostructures rapidly is akey to high-throughput functional materials discovery. In addition to beingtime-consuming, a majority of conventional materials synthesis processesclosely follow thermodynamics equilibria, which limit the discovery of newclasses of metastable phases such as high entropy oxides (HEO). Herein, aphotonic flash synthesis of HEO nanoparticles at timescales of millisecondsis demonstrated. By leveraging the abrupt heating and cooling cycles inducedby a high-power-density xenon pulsed light, mixed transition metal saltprecursors undergo rapid chemical transformations. Hence, nanoparticlesform within milliseconds with a strong affinity to bind to the carbon substrate.Oxygen evolution reaction (OER) activity measurements of the synthesizednanoparticles demonstrate two orders of magnitude prolonged stability athigh current densities, without noticeable decay in performance, compared tocommercial IrO2catalyst. This superior catalytic activity originates from thesynergistic effect of different alloying elements mixed at a high entropic state.It is found that Cr addition influences surface activity the most by promotinghigher oxidation states, favoring optimal interaction with OER intermediates.The proposed high-throughput method opens new pathways towarddeveloping next-generation functional materials for various electronics,sensing, and environmental applications, in addition to renewable energyconversion.

The development of multifunctional non-precious transition metal electrocatalysts is technologically significant in hydrogen and oxygen electrochemistry but challenging. Here we exploit interface engineering to construct a novel interface catalyst of Ni3N and Co2N that exhibits multifunctional hydrogen and oxygen electrochemical activities in alkaline media. The interface catalysts of Ni3N/Co2N show superior bifunctional activity for hydrogen electrochemistry comparable to the state-of-the-art Pt catalyst, as well as high oxygen evolution reaction activity. Furthermore, the multifunctional Ni3N/Co2N interface electrocatalysts demonstrate excellent applications in water splitting for H2 generation and a highly stable Swagelok-type Ni–H battery for H2 utilization. Density functional theory calculations further confirm that the interfacial charge transfer from Ni to Co and N in Ni3N/Co2N efficiently enhances the dissociative adsorption of H2 and optimizes the adsorption configurations and binding energies of the intermediate hydrogen and hydroxide in the multifunctional reactions.

The development of active, durable, and nonprecious electrocatalysts for hydrogen electrochemistry is highly desirable but challenging. In this work, we design and fabricate a novel interface catalyst of Ni and Co₂N (Ni/Co₂N) for hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). The Ni/Co₂N interfacial catalysts not only achieve a current density of −10.0 mA cm^–2 with an overpotential of 16.2 mV for HER but also provide a HOR current density of 2.35 mA cm^–2 at 0.1 V vs reversible hydrogen electrode (RHE). Furthermore, the electrode couple made of the Ni/Co₂N interfacial catalysts requires only a cell voltage of 1.57 V to gain a current density of 10 mA cm^–2 for overall water splitting. Hybridizations in the three elements of Ni-3d, N-2p, and Co-3d result in charge transfer in the interfacial junction of the Ni and Co₂N materials. Our density functional theory calculations show that both the interfacial N and Co sites of Ni/Co₂N prefer to hydrogen adsorption in the hydrogen catalytic activities. This study provides a new approach for the construction of multifunctional catalysts for hydrogen electrochemistry.

Many of the existing electrochemical catalysts suffer from poor selectivity, instability, and low exchange current densities. These shortcomings call for a comprehensive exploration of the catalytic processes at the fundamental nanometer length scale levels. Here we exploit infrared (IR) nanoimaging and nanospectroscopy to directly visualize catalytic reactions on the surface of Cu₂O polyhedral single crystals with nanoscale spatial resolution. Nano-IR data revealed signatures of this common catalyst after electrochemical reduction of carbon dioxides (CO₂). We discuss the utility of nano-IR methods for surface/facet engineering of efficient electrochemical catalysts.

According to density functional theory, monolayer (ML) MoS₂ is predicted to possess electrocatalytic activity for the hydrogen evolution reaction (HER) that approaches that of platinum. However, its observed HER activity is much lower, which is widely believed to result from a large Schottky barrier between ML MoS₂ and its electrical contact. In order to better understand the role of contact resistance in limiting the performance of ML MoS₂ HER electrocatalysts, this study has employed well-defined test platforms that allow for the simultaneous measurement of contact resistance and electrocatalytic activity toward the HER during electrochemical testing. At open circuit potential, these measurements reveal that a 0.5 M H₂SO₄ electrolyte can act as a strong p-dopant that depletes free electrons in MoS₂ and leads to extremely high contact resistance, even if the contact resistance of the as-made device in air is originally very low. However, under applied negative potentials this doping is mitigated by a strong electrolyte-mediated gating effect which can reduce the contact and sheet resistances of properly configured ML MoS₂ electrocatalysts by more than 5 orders of magnitude. At potentials relevant to HER, the contact resistance becomes negligible and the performance of MoS₂ electrodes is limited by HER kinetics. These findings have important implications for the design of low-dimensional semiconducting electrocatalysts and photocatalysts.