Three classes (carbides, nitrides and oxides) of nanoscaled early-transition-metal catalysts have been proposed to replace the expensive Pt catalyst as counter electrodes (CEs) in dye-sensitized solar cells (DSCs). Of these catalysts, Cr(3)C(2), CrN, VC(N), VN, TiC, TiC(N), TiN, and V(2)O(3) all showed excellent catalytic activity for the reduction of I(3)(-) to I(-) in the electrolyte. Further, VC embedded in mesoporous carbon (VC-MC) was prepared through in situ synthesis. The I(3)(-)/I(-) DSC based on the VC-MC CE reached a high power conversion efficiency (PCE) of 7.63%, comparable to the photovoltaic performance of the DSC using a Pt CE (7.50%). In addition, the carbide catalysts demonstrated catalytic activity higher than that of Pt for the regeneration of a new organic redox couple of T(2)/T(-). The T(2)/T(-) DSCs using TiC and VC-MC CEs showed PCEs of 4.96 and 5.15%, much higher than that of the DSC using a Pt CE (3.66%). This work expands the list of potential CE catalysts, which can help reduce the cost of DSCs and thereby encourage their fundamental research and commercial application.

Electronic skin (e-skin) has been under the spotlight due to great potential for applications in robotics, human-machine interfaces, and healthcare. Meanwhile, triboelectric nanogenerators (TENGs) have been emerging as an effective approach to realize self-powered e-skin sensors. In this work, bioinspired TENGs as self-powered e-skin sensors are developed and their applications for robotic tactile sensing are also demonstrated. Through the facile replication of the surface morphology of natural plants, the interlocking microstructures are generated on tribo-layers to enhance triboelectric effects. Along with the adoption of polytetrafluoroethylene (PTFE) tinny burrs on the microstructured tribo-surface, the sensitivity for pressure measurement is boosted with a 14-fold increase. The tactile sensing capability of the TENG e-skin sensors are demonstrated through the characterizations of handshaking pressure and bending angles of each finger of a bionic hand during handshaking with human. The TENG e-skin sensors can also be utilized for tactile object recognition to measure surface roughness and discern hardness. The facile fabrication scheme of the self-powered TENG e-skin sensors enables their great potential for applications in robotic dexterous manipulation, prosthetics, human-machine interfaces, etc.

The design and fabrication of 2D nanostructure electrodes with desired electrochemical activities is highly demanded for electrocatalysis and supercapacitors. Herein, the tuned fabrication of ultrathin and tortuous nickel/cobalt-layered double hydroxide (NiCo-LDH) nanosheets via a graphene oxide (GO) surface-confined strategy is reported, yielding nanosheets with a thickness of 1.7-1.8 nm that is duplicated from the graphene oxides in terms of both the lateral size and the shape. It has been found that the C/O functional groups on the GO surface have functioned to promote the oxidation of Co 2+ to Co 3+ , and to transform the β-phase NiCo-hydroxide (NiCo-OH) into the LDH-phase with tuned homogenous composition and geometry. The ultrathin NiCo-LDH nanosheets mimic the morphology and size of the graphene due to the surface-confined and/or surface-guided growth. The as-obtained NiCo-LDH-graphene (NiCo-LDH-G) nanosheets exhibit a superior electrocatalytic activity for oxygen evolution reaction, evidenced by a small overpotential of 0.337 V (@10 mA cm −2 in 0.1 m KOH electrolyte), and a high charge storage capability of 1489 F g −1 as electrodes for supercapacitors. This 2D surface-confined growth strategy may pave a way for the fabrication of ultrathin 2D materials including but not limited to transition metal hydroxides for high-performance electrochemical applications.