The intermittent nature of renewable energy sources sets a requirement for efficient energy storage to mitigate the conflict between energy supply and demand. Hydrogen is a promising choice for energy storage due to its high energy density. However, the conversion of electrical energy to chemical energy stored in hydrogen through water electrolysis suffers from low efficiency, and the electricity cost dominates the total cost of hydrogen production. Here, we report the study of improving the hydrogen evolution reaction activity of Pt-based catalysts by building a nanoscale surface NiO and Pt interface, further optimizing the performance via tuning the lattice parameter of the core of nanoparticles, which can be achieved by varying the dealloying annealing time. The optimized PtCuNi-O/C and PtNi-O/C catalysts are demonstrated to be one of the best catalysts, with a mass activity (MA) of 9.1 and 8.7 mA/µg_Pt, which is 9.9-fold and 9.5-fold of that of Pt/C, respectively.

The development of pressure sensor arrays capable of distinguishing the shape and texture details of objects is of considerable interest in the emerging fields of smart robots, prostheses, human–machine interfaces, and artificial intelligence (AI). Here we report an integrated pressure sensor array, by combining solution-processed two-dimensional (2D) MoS₂ van der Waals (vdW) thin film transistor (TFT) active matrix and conductive micropyramidal pressure-sensitive rubber (PSR) electrodes made of polydimethylsiloxane/ carbon nanotube composites, to achieve spatially revolved pressure mapping with excellent contrast and low power consumption. We demonstrate a 10 × 10 active matrix by using the 2D MoS₂ vdW-TFTs with high on-off ratio > 10⁶, minimal hysteresis, and excellent device-to-device uniformity. The combination of the vdW-TFT active matrix with the highly uniform micropyramidal PSR electrodes creates an integrated pressure sensing array for spatially resolved pressure mapping. This study demonstrates that the solution-processed 2D vdW-TFTs offer a solution for active-matrix control of pressure sensor arrays, and could be extended for other active-matrix arrays of electronic or optoelectronic devices.

Developing highly efficient electrochemical catalysts for carbon dioxide reduction reaction (CO₂RR) provides a solution to battle global warming issues resulting from ever-increasing carbon footprint due to human activities. Copper (Cu) is known for its efficiency in CO₂RR towards value-added hydrocarbons; hence its unique structural properties along with various Cu alloys have been extensively explored in the past decade. Here, we demonstrate a two-step approach to achieve intimate atomic Cu-Ag interfaces on the surface of Cu nanowires, which show greatly improved CO₂RR selectivity towards methane (CH₄). The specially designed Cu-Ag interfaces showed an impressive maximum Faradaic efficiency (FE) of 72% towards CH₄ production at -1.17 V (vs. reversible hydrogen electrode (RHE)).

Systematic control of grain boundary densities in various platinum (Pt) nanostructures was achieved by specific peptide-assisted assembly and coagulation of nanocrystals. A positive quadratic correlation was observed between the oxygen reduction reaction (ORR) specific activities of the Pt nanostructures and the grain boundary densities on their surfaces. Compared to commercial Pt/C, the grain-boundary-rich strain-free Pt ultrathin nanoplates demonstrated a 15.5 times higher specific activity and a 13.7 times higher mass activity. Simulation studies suggested that the specific activity of ORR was proportional to the resident number and the resident time of oxygen on the catalyst surface, both of which correlate positively with grain boundary density, leading to improved ORR activities.

Direct ethanol fuel cell (DEFC) has received tremendous research interests because of the more convenient storage and transportation of ethanol vs. compressed hydrogen. However, the electrocatalytic ethanol oxidation reaction typically requires precious metal catalysts and is plagued with relatively high over potential and low mass activity. Here we report the synthesis of Pt₃Ag alloy wavy nanowires via a particle attachment mechanism in a facile solvothermal process. Transmission microscopy studies and elemental analyses show highly wavy nanowire structures with an average diameter of 4.6 ± 1.0 nm and uniform Pt₃Ag alloy formation. Electrocatalytic studies demonstrate that the resulting alloy nanowires can function as highly effective electrocatalysts for ethanol oxidation reactions (EOR) with ultrahigh specific activity of 28.0 mA/cm² and mass activity of 6.1 A/mg, far exceeding that of the commercial Pt/carbon samples (1.10 A/mg). The improved electrocatalytic activity may be partly attributed to partial electron transfer from Ag to Pt in the Pt₃Ag alloy, which weakens CO binding and the CO poisoning effect. The one-dimensional nanowire morphology also contributes to favorable charge transport properties that are critical for extracting charge from catalytic active sites to external circuits. The chronoamperometry studies demonstrate considerably improved stability for long term operation compared with the commercial Pt/C samples, making the Pt₃Ag wavy nanowires an attractive electrocatalyst for EOR.

Benzaldehyde byproduct is an imperative intermediate in the production of fine chemicals and additives. Tuning selectivity to benzaldehyde is therefore critical in alcohol oxidation reactions at the industrial level. Herein, we report a simple but innovative method for the synthesis of palladium hydride and nickel palladium hydride nanodendrites with controllable morphology, high stability, and excellent catalytic activity. The synthesized dendrites can maintain the palladium hydride phase even after their use in the chosen catalytic reaction. Remarkably, the high surface area morphology and unique interaction between nickel-rich surface and palladium hydride (β-phase) of these nanodendrites are translated in an enhanced catalytic activity for benzyl alcohol oxidation reaction. Our Ni/PdH_0.43 nanodendrites demonstrated a high selectivity towards benzaldehyde of about 92.0% with a conversion rate of 95.4%, showing higher catalytic selectivity than their PdH_0.43 counterparts and commercial Pd/C. The present study opens the door for further exploration of metal/metal-hydride nanostructures as next-generation catalytic materials.

Direct methanol fuel cells (DMFCs) have received tremendous research interests because of the facile storage of liquid methanol vs. hydrogen. However, the DMFC today is severely plagued by the poor kinetics and rather high overpotential in methanol oxidation reaction (MOR). Here we report the investigation of the ultrathin Rh wavy nanowires as a highly effective MOR electrocatalyst. We show that ultrathin wavy Rh nanowires can be robustly synthesized with 2-3 nm diameters. Electrochemical studies show a current peak at the potential of 0.61 V vs. reversible hydrogen electrode (RHE), considerably lower than that of Pt based catalysts (~ 0.8-0.9 V vs. RHE). Importantly, with ultrathin diameters and favorable charge transport, the Rh nanowires catalysts exhibit an ultrahigh electrochemically active surface area determined from CO-stripping (ECSA_CO) of 144.2 m²/g, far exceeding that of the commercial Rh black samples (20 m²/g). Together, the Rh nanowire catalysts deliver a mass activity of 722 mA/mg at 0.61 V, considerably higher than many previously reported electrocatalysts at the same potential. The chronoamperometry studies also demonstrate good stability and CO-tolerance compared with the Rh black control sample, making ultrathin Rh wavy nanowires an attractive electrocatalyst for MOR.

Controlled syntheses of PtNi metal nanocrystals with unique structures for catalyzing oxygen reduction reactions (ORRs) have attracted great interest. Here, we report the one-step synthesis of single-crystal PtNi octahedra with in situ-developed highly concave features and self-confined composition that are optimal for ORR. Detailed studies revealed that the Pt-rich seeding, subsequent Pt/Ni co-reduction, and Pt–Ni interfusion resulted in uniform single-crystal PtNi octahedra, and that the combination of Ni facet segregation and oxygen etching of a Ni-rich surface led to the concavity and confined Ni content. The concave PtNi nanocrystals exhibited much higher ORR performance than the commercially available Pt/C catalyst in terms of both specific activity (29.1 times higher) and mass activity (12.9 times higher) at 0.9 V (vs. reversible hydrogen electrode (RHE)). The performance was also higher than that of PtNi octahedra without concavity, confirming that the higher activity was closely related to its morphology. Moreover, the concave octahedra also exhibited remarkable stability in ORR (93% mass activity remained after 10, 000 cycles between 0.6 and 1.1 V vs. RHE) owing to the passivation of the unstable sites.