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There is growing acknowledgment that the properties of the electrochemical interfaces play an increasingly pivotal role in improving the performance of the hydrogen evolution reaction (HER). Here, we present, for the first time, direct dynamic spectral evidence illustrating the impact of the interaction between interfacial water molecules and adsorbed hydroxyl species (OHad) on the HER properties of Ni(OH)2using Au/core-Ni(OH)2/shell nanoparticle-enhanced Raman spectroscopy. Notably, our findings highlight that the interaction between OHadand interfacial water molecules promotes the formation of weakly hydrogen-bonded water, fostering an environment conducive to improving the HER performance. Furthermore, the participation of OHadin the reaction is substantiated by the observed deprotonation step of Au@2 nm Ni(OH)2during the HER process. This phenomenon is corroborated by the phase transition of Ni(OH)2to NiO, as verified through Raman and X-ray photoelectron spectroscopy. The significant redshift in the OH-stretching frequency of water molecules during the phase transition confirms that surface OHaddisrupts the hydrogen-bond network of interfacial water molecules. Through manipulation of the shell thickness of Au@Ni(OH)2, we additionally validate the interaction between OHadand interfacial water molecules. In summary, our insights emphasize the potential of electrochemical interfacial engineering as a potent approach to enhance electrocatalytic performance.

Directly monitoring the oxygen reduction reaction (ORR) process in situ is very important to deeply understand the reaction mechanism and is a critical guideline for the design of high-efficiency catalysts, but there is still lack of definite in situ evidence to clarify the effect between adsorbed intermediates and the strain/electronic effect for enhanced ORR performance. Herein, in situ surface-enhanced Raman spectroscopy (SERS) was employed to detect the intermediates during the ORR process on the Au@Pd@Pt core/shell heterogeneous nanoparticles (NPs). Direct spectroscopic evidence of the *OOH intermediate was obtained, and an obvious red shift of the *OOH frequency was identified with the controllable shell thickness of Pd. Detailed experimental characterizations and density functional theory (DFT) calculations demonstrated that such improved ORR activity after inducing Pd into Au@Pt NPs can be attributed to the optimized adsorbate–substrate interaction due to the strain and electronic effect, leading to a higher Pt–O binding energy and a lower O–O binding energy, which was conducive to O–O dissociation and promoted the subsequent reaction. Notably, this work illustrates a relationship between the performance and strain/electronic effect via the intermediate detected by SERS and paves the way for the construction of ORR electrocatalysts with high performance.

PtNi alloy catalysts have excellent catalytic activity and are considered some of the most promising electrocatalysts capable of replacing pure Pt for the oxygen reduction reaction (ORR). For PtNi alloys, Ni-doping can improve performance by changing the electronic and structural properties of the catalyst surface and its interaction with reaction intermediates. However, to date there is no direct spectral evidence detecting or identifying the effect of Ni on the ORR in PtNi alloy catalysts. Herein, we introduce a surface-enhanced Raman spectroscopic (SERS) “borrowing” strategy for investigating ORR processes catalyzed by Au@PtNi nanoparticles (NPs). The bond vibration of adsorbed peroxide intermediate species (*OOH) was obtained, and the effect of Ni on the interaction between surface Pt and *OOH was studied by varying the Ni content in the alloy. The frequency of the *OOH spectral band has an obvious red-shift with increasing Ni content. Combined with density functional theory (DFT) calculations, we show that Ni-doping can optimize *OOH surface binding on the Pt surface, achieving more efficient electron transfer, thus improving the ORR rate. Notably, these results evidence the SERS borrowing strategy as an effective technique for in situobservations of catalytic processes.

We demonstrate that copper-based super-thin high-efficiency boiling heat transfer (BHT) interfaces can be obtained via electroplating hierarchical nickel nanocone coverings on the surface of copper nanocone cores. By regulating surface morphologies, wettability, and mass and heat transfer properties of hierarchical structures, we reveal the regulation rules of their performance. Based on this, we obtain the optimized BHT interfaces with a thickness of only 6.4 μm, which shows 228% enhancement in the maximal heat transfer coefficient, 71% enhancement in the critical heat flux, and 68% decrease in the superheat for the onset of nucleate boiling, as compared to the flat copper surface. Our studies clearly indicate that, although the in situ growth of nickel nanocones can unavoidably increase the interface thermal resistance of hierarchical structures, its optimization can still enhance BHT performance. This may be ascribed to the coupling of several interface effects such as more heat transfer area, more nucleation sites, smaller bubble departure sizes, and stronger liquid supply ability caused by hierarchical structures. Our work opens up a new avenue for the development of copper-based super-thin high-efficiency BHT interfaces, which would help enhance the efficiency of energy utilization and heat dissipation of various thermal devices.

Nanoparticles with a 55 nm Au core and a few monolayers of Pt shell (denoted as Au@PtxML, x= 1–4) are found to have superior activity toward the oxygen reduction reaction (ORR) compared to commercial Pt nanoparticles and polycrystalline Pt (pc-Pt) electrodes in 0.1 M HClO4. The half-wave potential for ORR at Au@Pt1 MLis ca. 20 mV positively shifted. With the decrease of the Pt shell thickness from 4 to 1 monolayer, both the extent of enhancement of the ORR activity and the adsorption strength of oxygen-containing species increase; the latter is confirmed by results from surface-enhanced Raman spectroscopy (SERS) and X-ray photon emission spectroscopy (XPS). Furthermore, SERS results also reveal that adsorbed CO on such catalysts displays a blue shift in Pt–CO and a red shift in C–O stretching frequencies compared to that at pc-Pt under otherwise identical conditions. Positive double layer effects induced by diminishing surface charge density, which leads to the less rigid first layer of water, are suggested to be the origin of the superior ORR performance of Au@PtxMLto that of commercial Pt/C catalysts.