Question: For which invention are both Christian Friedrich Schönbein, a the German-Swiss chemist and William Robert Grove, the Welsh judge and physical scientist given credit?
Context: Yards from scrimmage is an American football and Canadian football statistical measure.  In the game of football, progress is measured by advancing the football towards the opposing team's goal line.  Progress can be made during play by the offensive team by advancing the ball from the point of progress at the start of play known as the line of scrimmage.  When the offensive team advances the ball by rushing the football, the player who carries the ball is given credit for the difference in progress measured in rushing yards.  When the offensive team advances the ball by pass reception, the player who catches the reception is given credit for the difference in progress measured in reception yards.  Although the ball may also be advanced by penalty these yards are not considered yards from scrimmage.  Progress lost via quarterback sacks are classified variously by league of play with rules having changed over time within some leagues.  The total of rushing yards and receiving yards is known as yards from scrimmage.  This definition of yardage differs from total offense which gives credit for passing yardage to the person throwing the football rather than receiving the football. Wilhelm Weith (9 May 1846, in Bad Homburg vor der Höhe – 29 November 1881, in Ajaccio) was a German-Swiss chemist. The principle of a fuel cell was discovered by Christian Friedrich Schönbein in 1838, and the first fuel cell was constructed by Sir William Robert Grove in 1839.  The fuel cells made at this time were most similar to today's phosphoric acid fuel cells.  Most hydrogen fuel cells today are of the proton exchange membrane (PEM) type.  A PEM converts the chemical energy released during the electrochemical reaction of hydrogen and oxygen into electrical energy.  The Energy Policy Act of 1992 was the first national legislation that called for large-scale hydrogen research.  A five-year program was conducted that investigated the production of hydrogen from renewable energy sources and the feasibility of existing natural gas pipelines to carry hydrogen.  It also called for the research into hydrogen storage systems for electric vehicles and the development of fuel cells suitable to power an electric motor vehicle. The Grove cell was an early electric primary cell named after its inventor, Welsh physical scientist William Robert Grove, and consisted of a zinc anode in dilute sulfuric acid and a platinum cathode in concentrated nitric acid, the two separated by a porous ceramic pot. All-purpose yards or all-purpose yardage is an American football and Canadian football statistical measure.  It is virtually the same as the statistic that some football leagues refer to as combined net yards.  In the game of football, progress is measured by advancing the football towards the opposing team's goal line.  Progress can be made during play by the offensive team by advancing the ball from its point of progress at the start of play known as the line of scrimmage or by the defensive team after taking possession of the football via a change of possession (such as punt, kickoff, interception, punt block, blocked kick or fumble).  When the offensive team advances the ball by rushing the football, the player who carries the ball is given credit for the difference in progress measured in rushing yards.  When the offensive team advances the ball by pass reception, the player who catches the reception is given credit for the difference in progress measured in reception yards.  Although the ball may also be advanced by penalty, these yards are not considered all-purpose yards.  Progress lost via quarterback sacks is classified variously.  Thus, all-purpose yards is a combined total of rushing yards, receiving yards, and all forms of return yards only.  Some sources do not specify which types of return yards count toward this total because the most common forms of return yards are kick and punt return yards. Pompejus Alexander Bolley (7 May 1812 in Heidelberg – 3 August 1870 in Zürich) was a German-Swiss chemist known for his work in dye chemistry. Christian Friedrich Schönbein (18 October 1799 – 29 August 1868) was a German-Swiss chemist who is best known for inventing the fuel cell (1838) at the same time as William Robert Grove, Robert Cumming and his discoveries of guncotton and ozone. Explosions-Polka, op.  43, is a polka written by Johann Strauss II in 1847.  The title was inspired by a discovery of guncotton or nitrocellulose by German scientist Christian Friedrich Schönbein in 1840.  The Viennese press eagerly reported this discovery many years later in 1846, describing many products that can then be made 'explosive'. Sir William Robert Grove, PC, FRS FRSE (11 July 1811 – 1 August 1896) was a Welsh judge and physical scientist.  He anticipated the general theory of the conservation of energy, and was a pioneer of fuel cell technology.  He invented the Grove voltaic cell. Böttger was born in Aschersleben, Germany in 1806.  After attending the primary school there he joined the school of the Franksche Stiftung in Halle an der Saale at the age of eleven.  In 1824, Böttger started to study theology, but in parallel also attended the science lectures at the University Halle.  The lectures of Johann Salomo Christoph Schweigger had a strong influence on him.  Böttger left the university in 1828 and worked as cleric and teacher at different locations.  The contact with Schweigger never faded and in 1831 Böttger decided to leave the theology career.  He was offered a job at the voluntary association for chemistry in Frankfurt in 1835.  His first major work in Frankfurt was the improvement of the electrotyping method for the production of printing plates.  Böttger received his PhD from the University of Jena in 1837 and was appointed as full professor in Frankfurt in 1842.  Böttger married Christiane Harpke in 1841, and they had eight children.  He and Christian Friedrich Schönbein, a German-Swiss chemist, discovered nitrocellulose independently in 1846.  Both scientists collaborated to earn money with the invention, but they were not successful.  The development of the safety match in 1848 and the synthesis of the first organocopper compound, the explosive copper(I) acetylide CuC in 1859 were examples for his chemistry research.  Böttger stayed at the University of Frankfurt am Main for the rest of his life, although he was offered positions at other universities.  He died of a liver illness in 1881.
Answer: fuel cell