Designing highly efficient electrocatalysts for oxygen evolution reaction (OER) plays a key role in the development of various renewable energy storage and conversion devices. In this work, we developed metallic Co4N porous nanowire arrays directly grown on flexible substrates as highly active OER electrocatalysts for the first time. Benefiting from the collaborative advantages of metallic character, 1D porous nanowire arrays, and unique 3D electrode configuration, surface oxidation activated Co4N porous nanowire arrays/carbon cloth achieved an extremely small overpotential of 257 mV at a current density of 10 mA cm(-2), and a low Tafel slope of 44 mV dec(-1) in an alkaline medium, which is the best OER performance among reported Co-based electrocatalysts to date. Moreover, in-depth mechanistic investigations demonstrate the active phases are the metallic Co4N core inside with a thin cobalt oxides/hydroxides shell during the OER process. Our finding introduces a new concept to explore the design of high-efficiency OER electrocatalysts.

Two Pt single-atom catalysts (SACs) of Pt-GDY1 and Pt-GDY2 were prepared on graphdiyne (GDY)supports. The isolated Pt atoms are dispersed on GDY through the coordination interactions between Pt atoms and alkynyl C atoms in GDY, with the formation of five-coordinated C -Pt-Cl species in Pt-GDY1 and four-coordinated C -Pt-Cl species in Pt-GDY2. Pt-GDY2 shows exceptionally high catalytic activity for the hydrogen evolution reaction (HER), with a mass activity up to 3.3 and 26.9 times more active than Pt-GDY1 and the state-of-the-art commercial Pt/C catalysts, respectively. Pt-GDY2 possesses higher total unoccupied density of states of Pt 5d orbital and close to zero value of Gibbs free energy of the hydrogen adsorption (|ΔGPtH* |) at the Pt active sites, which are responsible for its excellent catalytic performance. This work can help better understand the structure-catalytic activity relationship in Pt SACs.

Designing highly efficient electrocatalysts for oxygen evolution reaction (OER) playsakey role in the development of various renewable energy storage and conversion devices.In this work, we developed metallic Co 4 Nporous nanowire arrays directly grown on flexible substrates as highly active OER electrocatalysts for the first time.B enefiting from the collaborative advantages of metallic character,1 Dp orous nanowire arrays,a nd unique 3D electrode configuration, surface oxidation activated Co 4 Np orous nanowire arrays/carbon cloth achieved an extremely small overpotential of 257 mV at ac urrent density of 10 mA cm À2 ,a nd al ow Tafel slope of 44 mV dec À1 in an alkaline medium, which is the best OER performance among reported Co-based electrocatalysts to date. Moreover,in-depth mechanistic investigations demonstrate the active phases are the metallic Co 4 Nc ore inside with at hin cobalt oxides/hydroxides shell during the OER process.O ur finding introduces anew concept to explore the design of highefficiency OER electrocatalysts.

Two-dimensional materials have been an ideal material platform for constructing flexible ultrathin-film supercapacitors, offering great advantages of flexibility, ultra-thinness and even transparency. Exploring new two-dimensional pseudocapacitive materials with high electrochemical activity is needed to achieve flexible ultrathin-film supercapacitors with higher energy densities. Here we report an inorganic graphene analogue, a 1 -vanadyl phosphate ultrathin nanosheets with less than six atomic layers, as a promising material to construct a flexible ultrathin-film pseudocapacitor in all-solid-state. The material exhibits a high potential plateau of B1.0 V in aqueous solutions, approaching the electrochemical potential window of water (1.23 V). The as-established flexible supercapacitor achieves a high redox potential (1.0 V) and a high areal capacitance of 8,360.5 mF cm À 2 , leading to a high energy density of 1.7 mWh cm À 2 and a power density of 5.2 mW cm À 2 .

Developing highly active catalysts for the oxygen evolution reaction (OER) is of paramount importance for designing various renewable energy storage and conversion devices. Herein, we report the synthesis of a category of Co-Pi analogue, namely cobalt-based borate (Co-Bi ) ultrathin nanosheets/graphene hybrid by a room-temperature synthesis approach. Benefiting from the high surface active sites exposure yield, enhanced electron transfer capacity, and strong synergetic coupled effect, this Co-Bi NS/G hybrid shows high catalytic activity with current density of 10 mA cm(-2) at overpotential of 290 mV and Tafel slope of 53 mV dec(-1) in alkaline medium. Moreover, Co-Bi NS/G electrocatalysts also exhibit promising performance under neutral conditions, with a low onset potential of 235 mV and high current density of 14.4 mA cm(-2) at 1.8 V, which is the best OER performance among well-developed Co-based OER electrocatalysts to date. Our finding paves a way to develop highly active OER electrocatalysts.

The reaction of precursors containing both nitrogen and oxygen atoms with Ni II under 500 8 8Cc an generate aN /O mixing coordinated Ni-N 3 Os ingle-atom catalyst (SAC) in which the oxygen atom can be gradually removed under high temperature due to the weaker NiÀOi nteraction, resulting in avacancy-defect Ni-N 3 -V SACatNisite under 800 8 8C. Forthe reaction of Ni II with the precursor simply containing nitrogen atoms,o nly an o-vacancy-defect Ni-N 4 SACw as obtained. Experimental and DFT calculations reveal that the presence of av acancy-defect in Ni-N 3 -V SACc an dramatically boost the electrocatalytic activity for CO 2 reduction, with extremely high CO 2 reduction current density of 65 mA cm À2 and high Faradaic efficiency over 90 %a tÀ0.9 Vv s. RHE, as well as arecordhigh turnover frequency of 1.35 10 5 h À1 ,muchhigher than those of Ni-N 4 SAC, and being one of the best reported electrocatalysts for CO 2 -to-CO conversion to date.

We report a facile one step method for fabricating g-C3N4nanosheets with enhanced photocatalytic H2evolution activity.

The design and synthesis of efficient metal‐free photoelectrocatalysts for water splitting are of great significance, as nonmetal elements are generally earth abundant and environment friendly. As a typical metal‐free semiconductor, g‐C3N4 has received much attention in the field of photocatalytic water splitting. However, the poor photoinduced hole mobility of g‐C3N4 restrains its catalytic performance. Herein, for the first time, graphdiyne (GDY) is used to interact with g‐C3N4 to construct a metal‐free 2D/2D heterojunction of g‐C3N4/GDY as an efficient photoelectrocatalyst for water splitting. The g‐C3N4/GDY photocathode exhibits enhanced photocarriers separation due to excellent hole transfer nature of graphdiyne and the structure of 2D/2D heterojunction of g‐C3N4/GDY, realizing a sevenfold increase in electron life time (610 μs) compared to that of g‐C3N4 (88 μs), and a threefold increase in photocurrent density (−98 μA cm−2) compared to that of g‐C3N4 photocathode (−32 μA cm−2) at a potential of 0 V versus normal hydrogen electrode (NHE) in neutral aqueous solution. The photoelectrocatalytic performance can be further improved by fabricating Pt@g‐C3N4/GDY, which displays an photocurrent of −133 μA cm−2 at a potential of 0 V versus NHE in neutral aqueous solution. This work provides a new strategy for the design of efficient metal‐free photoelectrocatalysts for water splitting.