Promoting the oxygen evolution reaction (OER) with saline water is highly desired to realize seawater splitting. This requires OER catalysts to resist serious corrosion and undesirable chloride oxidation. We introduce a 5d transition metal, Ir, to develop a monolayer NiIr-layered double hydroxide (NiIr-LDH) as the catalyst with enhanced OER performance for seawater splitting. The NiIr-LDH catalyst delivers 500 mA/cm 2 at only 361 mV overpotential with ∼99% O 2 Faradaic efficiency in alkaline seawater, which is more active than commercial IrO 2 (763 mV, 23%) and the best known OER catalyst NiFe-LDH (530 mV, 92%). Moreover, it shows negligible activity loss at up to 650 h chronopotentiometry measurements at an industrial level (500 mA/cm 2 ), while commercial IrO 2 and NiFe-LDH rapidly deactivated within 0.2 and 10 h, respectively. The incorporation of Ir into the Ni(OH) 2 layer greatly altered the electron density of Ir and Ni sites, which was revealed by X-ray absorption fine structure and density functional theory (DFT) calculations. Coupling the electrochemical measurements and in situ Raman spectrum with DFT calculations, we further confirm that the generation of rate-limiting intermediate *O and *OOH species was accelerated on Ni and Ir sites, respectively, which is responsible for the high seawater splitting performance. Our results also provide an opportunity to fabricate LDH materials containing 5d metals for applications beyond seawater splitting.

The electrocatalytic conversion of CO 2 into valueadded chemicals is apromising approach to realize ac arbonenergy balance.H owever,l ow current density still limits the application of the CO 2 electroreduction reaction (CO 2 RR). Metal-organic frameworks (MOFs) are one class of promising alternatives for the CO 2 RR due to their periodically arranged isolated metal active sites.H owever,t he poor conductivity of traditional MOFs usually results in al ow current density in CO 2 RR. We have prepared conductive two-dimensional (2D) phthalocyanine-based MOF (NiPc-NiO 4 )n anosheets linked by nickel-catecholate,w hichc an be employed as highly efficient electrocatalysts for the CO 2 RR to CO.T he obtained NiPc-NiO 4 has ag ood conductivity and exhibited av ery high selectivity of 98.4 %t oward CO production and al arge CO partial current density of 34.5 mA cm À2 ,o utperforming the reported MOF catalysts.T his work highlights the potential of conductive crystalline frameworks in electrocatalysis.

Herein, an effective tandem catalysis strategy is developed to improve the selectivity of the CO 2 RR towards C 2 H 4 by multiple distinct catalytic sites in local vicinity.A n earth-abundant elements-based tandem electrocatalyst PTF-(Ni)/Cu is constructed by uniformly dispersing Cu nanoparticles (NPs) on the porphyrinic triazine framework anchored with atomically isolated nickel-nitrogen sites (PTF(Ni)) for the enhanced CO 2 RR to produce C 2 H 4 .T he Faradaic efficiency of C 2 H 4 reaches 57.3 %a tÀ1.1 Vv ersus the reversible hydrogen electrode (RHE), whichi sa bout 6t imes higher than the non-tandem catalyst PTF/Cu, whichproduces CH 4 as the major carbon product. The operando infrared spectroscopya nd theoretic density functional theory (DFT) calculations reveal that the local high concentration of CO generated by PTF(Ni)s ites can facilitate the CÀCc oupling to form C 2 H 4 on the nearby Cu NP sites.T he work offers an effective avenue to design electrocatalysts for the highly selective CO 2 RR to produce multicarbon products via atandem route.