Cost-effective electrocatalysts for the oxygen evolution reaction (OER) are critical to energy conversion and storage processes. A novel strategy is used to synthesize a non-noble-metal-based electrocatalyst of the OER by finely combining layered FeNi double hydroxide that is catalytically active and electric conducting graphene sheets, taking advantage of the electrostatic attraction between the two positively charged nanosheets. The synergy between the catalytic activity of the double hydroxide and the enhanced electron transport arising from the graphene resulted in superior electrocatalytic properties of the FeNi-GO hybrids for the OER with overpotentials as low as 0.21 V, which was further reduced to 0.195 V after the reduction treatment. Moreover, the turnover frequency at the overpotential of 0.3 V has reached 1 s(-1), which is much higher than those previously reported for non-noble-metal-based electrocatalysts.

The maintenance of cellular phosphate (Pi) homeostasis is of great importance in living organisms. The SPX domain-containing protein 1 (SPX1) proteins from both Arabidopsis and rice have been proposed to act as sensors of Pi status. The molecular signal indicating the cellular Pi status and regulating Pi homeostasis in plants, however, remains to be identified, as Pi itself does not bind to the SPX domain. Here, we report the identification of the inositol pyrophosphate InsP 8 as a signaling molecule that regulates Pi homeostasis in Arabidopsis. Polyacrylamide gel electrophoresis profiling of InsPs revealed that InsP 8 level positively correlates with cellular Pi concentration. We demonstrated that the homologs of diphosphoinositol pentakisphosphate kinase (PPIP5K), VIH1 and VIH2, function redundantly to synthesize InsP 8 , and that the vih1 vih2 double mutant overaccumulates Pi. SPX1 directly interacts with PHR1, the central regulator of Pi starvation responses, to inhibit its function under Pi-replete conditions. However, this interaction is compromised in the vih1 vih2 double mutant, resulting in the constitutive induction of Pi starvation-induced genes, indicating that plant cells cannot sense cellular Pi status without InsP 8 . Furthermore, we showed that InsP 8 could directly bind to the SPX domain of SPX1 and is essential for the interaction between SPX1 and PHR1. Collectively, our study suggests that InsP 8 is the intracellular Pi signaling molecule serving as the ligand of SPX1 for controlling Pi homeostasis in plants.